Difference between revisions of "GRUB"

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{{Article summary text|{{Boot process overview}}}}
 
{{Article summary text|{{Boot process overview}}}}
 
{{Article summary heading|Related}}
 
{{Article summary heading|Related}}
{{Article summary wiki|Burg}} - Burg is a brand-new boot loader based on GRUB2. It uses a new object format which allows it to be built in a wider range of OS, including Linux, Windows, OS X, Solaris, FreeBSD, etc. It also has a highly configurable menu system which works in both text and graphic mode.  
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{{Article summary wiki|BURG}} - BURG is a brand-new boot loader based on GRUB2. It can be built on a wider range of OS, and has a highly configurable menu system which works in both text and graphic mode.
 +
{{Article summary wiki|GRUB Legacy}} - previous Version, now obsolete.
 
{{Article summary heading|Resources}}
 
{{Article summary heading|Resources}}
{{Article summary wiki|GRUB_EFI_Examples}}
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{{Article summary wiki|GRUB EFI Examples}}
{{Article summary link|GNU GRUB -- GNU Project|https://www.gnu.org/software/grub/}}
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{{Article summary link|GNU GRUB - GNU Project|https://www.gnu.org/software/grub/}}
 
{{Article summary end}}
 
{{Article summary end}}
 
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[https://www.gnu.org/software/grub/ GRUB] - not to be confused with [[GRUB Legacy]] - is the next generation of the GRand Unified Bootloader. GRUB is derived from [http://www.nongnu.org/pupa/ PUPA] which was a research project to develop the next generation of what is now GRUB Legacy. GRUB has been rewritten from scratch to clean up everything and provide modularity and portability [https://www.gnu.org/software/grub/grub-faq.html#q1].
{{Merge|Network_Installation_Guide#GRUB|No mention of PXE capability in this article}}
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[https://www.gnu.org/software/grub/ GRUB2] is the next generation of the GRand Unified Bootloader (GRUB). GRUB2 is derived from [http://www.nongnu.org/pupa/ PUPA] which was a research project to investigate the next generation of GRUB. GRUB2 has been rewritten from scratch to clean up everything and provide modularity and portability [https://www.gnu.org/software/grub/grub-faq.html#q1].
+
  
 
In brief, the ''bootloader'' is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the Linux kernel. The kernel, in turn, initializes the rest of the operating system.
 
In brief, the ''bootloader'' is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the Linux kernel. The kernel, in turn, initializes the rest of the operating system.
  
 
== Preface ==
 
== Preface ==
Here is some information that needs to be clarified:
 
 
* The name ''GRUB'' officially refers to version ''2'' of the software, see [https://www.gnu.org/software/grub/]. If you are looking for the article on the legacy version, see [[GRUB Legacy]].
 
* The name ''GRUB'' officially refers to version ''2'' of the software, see [https://www.gnu.org/software/grub/]. If you are looking for the article on the legacy version, see [[GRUB Legacy]].
 +
* GRUB supports [[Btrfs]] as root (without a separate {{ic|/boot}} filesystem) compressed with either zlib or LZO.
  
* From 1.99-6 onwards, GRUB2 supports [[Btrfs]] as root (without a separate {{ic|/boot}} filesystem) compressed with either zlib or LZO.
+
=== Notes for current GRUB Legacy users ===
 +
* Upgrade from [[GRUB Legacy]] to GRUB is the much same as fresh installing GRUB which is covered [[#Installation|below]].
 +
* There are differences in the commands of GRUB Legacy and GRUB. Familiarize yourself with [https://www.gnu.org/software/grub/manual/grub.html#Commands GRUB commands] before proceeding (e.g. "find" has been replaced with "search").
 +
* GRUB is now ''modular'' and no longer requires "stage 1.5". As a result, the bootloader itself is limited -- modules are loaded from the hard drive as needed to expand functionality (e.g. for [[LVM]] or RAID support).
 +
* Device naming has changed between GRUB Legacy and GRUB. Partitions are numbered from 1 instead of 0 while drives are still numbered from 0, and prefixed with partition-table type. For example, {{ic|/dev/sda1}} would be referred to as {{ic|(hd0,msdos1)}} (for MBR) or {{ic|(hd0,gpt1)}} (for GPT).
  
* For GRUB2 UEFI info, it is recommended to read the [[UEFI]], [[GPT]] and [[UEFI_Bootloaders]] pages before reading this page.
+
==== Backup Important Data ====
  
=== Notes for current GRUB Legacy users ===
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Although a GRUB installation should run smoothly, it is strongly recommended to keep the GRUB Legacy files before upgrading to GRUB2.
* Upgrade from [[GRUB Legacy]] to [[GRUB]](2) is the much same as fresh installing GRUB(2)which is covered [[#Installation|below]].
+
  
* There are differences in the commands of GRUB and GRUB2. Familiarize yourself with [https://www.gnu.org/software/grub/manual/grub.html#Commands GRUB2 commands] before proceeding (e.g. "find" has been replaced with "search").
+
# mv /boot/grub /boot/grub-legacy
  
* GRUB2 is now ''modular'' and no longer requires "stage 1.5". As a result, the bootloader itself is limited -- modules are loaded from the hard drive as needed to expand functionality (e.g. for [[LVM]] or RAID support).
+
Backup the MBR which contains the boot code and partition table (Replace {{ic|/dev/sd'''X'''}} with your actual disk path)
  
* Device naming has changed between GRUB and GRUB2. Partitions are numbered from 1 instead of 0 while drives are still numbered from 0, and prefixed with partition-table type. For example, {{ic|/dev/sda1}} would be referred to as {{ic|(hd0,msdos1)}} (for MBR) or {{ic|(hd0,gpt1)}} (for GPT) using GRUB2.
+
# dd if=/dev/sdX of=/path/to/backup/mbr_backup bs=512 count=1
  
=== Preliminary Requirements for GRUB2 ===
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Only 446 bytes of the MBR contain boot code, the next 64 contain the partition table. If you do not want to overwrite your partition table when restoring, it is strongly advised to backup only the MBR boot code:
  
==== BIOS systems ====
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# dd if=/dev/sdX of=/path/to/backup/bootcode_backup bs=446 count=1
  
===== [[GPT]] specific instructions =====
+
If unable to install GRUB2 correctly, see [[#Restore GRUB Legacy]].
  
GRUB2 in BIOS-GPT configuration requires a [http://www.gnu.org/software/grub/manual/html_node/BIOS-installation.html#BIOS-installation BIOS Boot Partition] to embed its {{ic|core.img}} in the absence of post-MBR gap in GPT partitioned systems (which is taken over by the GPT Primary Header and Primary Partition table). This partition is used by GRUB2 only in BIOS-GPT setups. No such partition type exists in case of MBR partitioning (at least not for GRUB2). This partition is also not required if the system is UEFI based, as no embedding of bootsectors takes place in that case. Syslinux does not require this partition.
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=== Preliminary Requirements ===
  
For a BIOS-GPT configuration, create a 2 MiB partition using cgdisk or GNU Parted with no filesystem. The location of the partition in the partition table does not matter but it should be within the first 2 TiB region of the disk. It is advisable to put it somewhere in the beginning of the disk before the {{ic|/boot}} partition. Set the partition type to "EF02" in cgdisk or {{ic|set <BOOT_PART_NUM> bios_grub on}} in GNU Parted.
+
==== BIOS systems ====
  
{{Note|This partition should be created before {{ic|grub-install}} or {{ic|grub-setup}} is run.}}
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===== [[GUID Partition Table]] (GPT) specific instructions =====
 +
GRUB in BIOS-GPT configuration requires a [http://www.gnu.org/software/grub/manual/html_node/BIOS-installation.html BIOS Boot Partition] to embed its {{ic|core.img}} in the absence of post-MBR gap in GPT partitioned systems (which is taken over by the GPT Primary Header and Primary Partition table). This partition is used by GRUB only in BIOS-GPT setups. No such partition type exists in case of MBR partitioning (at least not for GRUB). This partition is also not required if the system is UEFI based, as no embedding of bootsectors takes place in that case.
  
===== [[MBR]] aka msdos partitioning specific instructions =====
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For a BIOS-GPT configuration, create a 1007 KiB partition at the beginning of the disk using cgdisk or GNU Parted with no filesystem. The size of 1007 KiB will allow for the following partition to be correctly alligned at 1024 KiB. If needed, the partition can also be located somewhere else on the disk, but it should be within the first 2 TiB region. Set the partition type to {{ic|0xEF02}} in gdisk, {{ic|EF02}} in cgdisk or {{ic|set <BOOT_PART_NUM> bios_grub on}} in GNU Parted.
  
Usually the post-MBR gap (after the 512 byte MBR region and before the start of the 1st partition) in many MBR (or msdos disklabel) partitioned systems is 31 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 to 2 MiB is recommended to provide sufficient room for embedding GRUB2's {{ic|core.img}} ({{bug|24103}}). It is advisable to use a partitioner which supports 1 MiB partition alignment to obtain this space as well as satisfy other non-512 byte sector issues (which are unrelated to embedding of {{ic|core.img}}).
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{{Note|This partition should be created before {{ic|grub-install}} or {{ic|grub-setup}} is run.}}
 +
{{Note|gdisk will only allow you to create this partition on the position which will waste the least amount of space (sector 34-2047) if you create it last, after all the other partitions. This is because gdisk will auto-align partitions to 2048-sector boundaries if possible.}}
  
MBR partitioning has better support in other operating systems, such as Microsoft Windows (up to Windows 7) and Haiku, than GPT partitioning. If you dual boot another operating system, consider using MBR partitioning.
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===== [[Master Boot Record]] (MBR) specific instructions =====
 +
Usually the post-MBR gap (after the 512 byte MBR region and before the start of the 1st partition) in many MBR (or msdos disklabel) partitioned systems is 31 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 to 2 MiB is recommended to provide sufficient room for embedding GRUB's {{ic|core.img}} ({{bug|24103}}). It is advisable to use a partitioner which supports 1 MiB partition alignment to obtain this space as well as satisfy other non-512 byte sector issues (which are unrelated to embedding of {{ic|core.img}}).
  
{{Warning|Create the 2MiB partition mentioned above BEFORE you convert to GPT. If you do not, gparted will not resize your boot partition to allow its creation, and when you reboot GRUB2 will not know where to look.}}
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MBR partitioning has better support than GPT partitioning in some operating systems, such as older versions of Microsoft Windows (up to Windows 7) and Haiku. If you dual boot such an operating system, consider using MBR partitioning.
  
[[GUID_Partition_Table#Convert_from_MBR_to_GPT]]
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A MBR disk may be convertible to GPT if there is a small amount of extra space available. See [[GUID Partition Table#Convert from MBR to GPT]].
  
 
==== UEFI systems ====
 
==== UEFI systems ====
===== Preface =====
+
{{Note|It is recommended to read and understand the [[Unified Extensible Firmware Interface|UEFI]], [[GUID Partition Table|GPT]] and [[UEFI Bootloaders]] pages.}}
{{Note|It is recommended to read and understand the [[UEFI]], [[GPT]] and [[UEFI_Bootloaders]] pages.}}
+
  
===== Create and Mount the UEFI SYSTEM PARTITION =====
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===== Create and Mount the UEFI System Partition =====
 
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Follow [[Unified Extensible Firmware Interface#EFI System Partition]] for instructions on creating a UEFI System Partition. Then mount the UEFI System Partition at {{ic|/boot/efi}}. If you have mounted the UEFI System Partition at some other mountpoint, replace {{ic|/boot/efi}} in the below instructions with that mountpoint:
Follow [[Unified_Extensible_Firmware_Interface#Create_an_UEFI_System_Partition_in_Linux]] for instructions on creating a UEFI SYSTEM PARTITION. Then mount the UEFI SYSTEM PARTITION at {{ic|/boot/efi}}. If you have mounted the UEFISYS partition in some other mountpoint, replace {{ic|/boot/efi}} in the below instructions with that mountpoint:
+
  
 
  # mkdir -p /boot/efi
 
  # mkdir -p /boot/efi
  # mount -t vfat <UEFISYS_PART_DEVICE> /boot/efi
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  # mount -t vfat <UEFI_SYSTEM_PARTITION> /boot/efi
  
Create a <UEFI_SYSTEM_PARTITION>{{ic|/EFI}} directory, if it does not exist:
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Create a {{ic|/boot/efi/EFI}} directory:
  
  # mkdir -p /boot/efi/EFI
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  # mkdir /boot/efi/EFI
  
 
== Installation ==
 
== Installation ==
Line 85: Line 87:
 
=== BIOS systems ===
 
=== BIOS systems ===
  
==== Backup Important Data ====
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GRUB can be [[pacman|installed]] with the {{Pkg|grub-bios}} package from the [[official repositories]]. It will replace {{Pkg|grub-legacy}} or {{Pkg|grub}}, if it is installed.
  
Although a GRUB(2) installation should run smoothly, it is strongly recommended to keep the GRUB Legacy files before installing {{Pkg|grub-bios}}.
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{{Note|Simply installing the package won't update the {{ic|/boot/grub/i386-pc/core.img}} file and the GRUB modules in {{ic|/boot/grub/i386-pc}}. You need to update them manually using {{ic|grub-install}} as explained below.}}
  
# mv /boot/grub /boot/grub-legacy
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==== Install boot files ====
  
Backup the MBR which contains the boot code and partition table (Replace {{ic|/dev/sd'''X'''}} with your actual disk path)
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There are 3 ways to install GRUB boot files in BIOS booting:
 +
*[[#Install to GPT BIOS Boot Partition]] (recommended with [[GPT]])
 +
*[[#Install to 440-byte MBR boot code region]] (recommended with [[MBR]])
 +
*[[#Install to Partition or Partitionless Disk]] (not recommended)
 +
*[[#Generate core.img alone]] (safest method, but requires another BIOS bootloader like [[GRUB Legacy]] or [[Syslinux]] to be installed to chainload {{ic|/boot/grub/i386-pc/core.img}})
  
# dd if=/dev/sdX of=/path/to/backup/mbr_backup bs=512 count=1
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{{Note|See http://www.gnu.org/software/grub/manual/html_node/BIOS-installation.html for additional documentation.}}
  
Only 446 bytes of the MBR contain boot code, the next 64 contain the partition table. If you do not want to overwrite your partition table when restoring, it is strongly advised to backup only the MBR boot code:
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===== Install to GPT BIOS Boot Partition =====
  
# dd if=/dev/sdX of=/path/to/backup/bootcode_backup bs=446 count=1
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[[GUID Partition Table]] disks do not have a reserved "boot track". Therefore you must create a BIOS Boot Partition ({{ic|0xEF02}}) to hold the GRUB core image.
  
If unable to install GRUB2 correctly, see [[GRUB2#Restore_GRUB_Legacy]].
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Using GNU Parted, you can set this using a command such as the following:
  
==== Install grub-bios package ====
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# parted /dev/disk set <partition-number> bios_grub on
  
The GRUB(2) packages can be installed with pacman (and will replace {{Pkg|grub-legacy}} or {{Pkg|grub}}, if it is installed):
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If you are using gdisk, set the partition type to {{ic|0xEF02}}. With partitioning programs that require setting the GUID directly, it should be {{ic|‘21686148-6449-6e6f-744e656564454649’}} (stored on disk as {{ic|"!haHdInotNeedEFI"}} if interpreted as ASCII).
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# pacman -S grub-bios
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{{Note|Simply installing the package won't update the {{ic|/boot/grub/i386-pc/core.img}} file and the GRUB(2) modules in {{ic|/boot/grub/i386-pc}}. You need to update them manually using {{ic|grub-install}} as explained below.}}
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{{Warning|Be very careful which partition you select when marking it as a BIOS Boot Partition. When GRUB finds a BIOS Boot Partition during installation, it will automatically overwrite part of it. Make sure that the partition does not contain any other data.}}
 
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==== Install grub-bios boot files ====
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There are 3 ways to install GRUB(2) boot files in BIOS booting:
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*[[#Install_to_440-byte_MBR_boot_code_region]] (recommended) ,  
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*[[#Install_to_Partition_or_Partitionless_Disk]] (not recommended),
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*[[#Generate_core.img_alone]] (safest method, but requires another BIOS bootloader like [[grub-legacy]] or [[syslinux]] to be installed to chainload {{ic|/boot/grub/i386-pc/core.img}}).
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+
===== Install to 440-byte MBR boot code region =====
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To setup {{ic|grub-bios}} in the 440-byte Master Boot Record boot code region, populate the {{ic|/boot/grub}} directory, generate the {{ic|/boot/grub/i386-pc/core.img}} file, and embed it in the 31 KiB (minimum size - varies depending on partition alignment) post-MBR gap (MBR disks) or in BIOS Boot Partition (GPT disks), run:
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To setup {{ic|grub-bios}} on a GPT disk, populate the {{ic|/boot/grub}} directory, generate the {{ic|/boot/grub/i386-pc/core.img}} file, and embed it in the BIOS Boot Partition, run:
  
 
  # modprobe dm-mod
 
  # modprobe dm-mod
Line 125: Line 120:
 
  # cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
 
  # cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
  
where {{ic|/dev/sda}} is the destination of the installation (in this case the MBR of the first SATA disk). If you use [[LVM]] for your {{ic|/boot}}, you can install GRUB2 on multiple physical disks.  
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where {{ic|/dev/sda}} is the destination of the installation.
  
{{Note|Without {{ic|--target}} or {{ic|--directory}} option, grub-install cannot determine for which firmware grub(2) is being installed. In such cases grub-install will show {{ic|source_dir doesn't exist. Please specify --target or --directory}} message. Also, {{ic|--target&#61;i386-pc}} is correct for 64-bit systems, as well.}}
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===== Install to 440-byte MBR boot code region =====
  
{{Note|After executing the {{ic|grub-install}} command, the directory {{ic|/boot/grub/locale}} may already exist, thus running {{ic|# mkdir -p /boot/grub/locale}} is obsolete.}}
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To setup {{ic|grub-bios}} in the 440-byte Master Boot Record boot code region, populate the {{ic|/boot/grub}} directory, generate the {{ic|/boot/grub/i386-pc/core.img}} file, embed it in the 31 KiB (minimum size - varies depending on partition alignment) post-MBR gap, and generate the configuration file, run:
  
The {{ic|--no-floppy}} tells {{ic|grub-bios}} utilities not to search for any floppy devices which reduces the overall execution time of {{ic|grub-install}} on many systems (it will also prevent the issue below from occurring). Otherwise you get an error that looks like this:
+
# modprobe dm-mod
 +
# grub-install --recheck /dev/sda
 +
# grub-mkconfig -o /boot/grub/grub.cfg
  
grub-probe: error: Cannot get the real path of '/dev/fd0'
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where {{ic|/dev/sda}} is the destination of the installation (in this case the MBR of the first SATA disk). If you use [[LVM]] for your {{ic|/boot}}, you can install GRUB on multiple physical disks.
Auto-detection of a filesystem module failed.
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Please specify the module with the option '--modules' explicitly.
+
  
{{Note|{{ic|--no-floppy}} has been removed from {{ic|grub-install}} in 2.00~beta2 upstream release, and replaced with {{ic|--allow-floppy}}.}}
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{{Warning|Make sure to check the {{ic|/boot}} directory if you use the latter. Sometimes the {{ic|boot-directory}} parameter creates another {{ic|/boot}} folder inside of {{ic|/boot}}. A wrong install would look like: {{ic|/boot/boot/grub/}}.}}
 
+
{{Warning|Make sure to check the {{ic|/boot}} directory if you use the latter. Sometimes the {{ic| boot-directory}} parameter creates another {{ic|/boot}} folder inside of {{ic|/boot}}. A wrong install would look like: {{ic|/boot/boot/grub/}}.}}
+
  
 
===== Install to Partition or Partitionless Disk =====
 
===== Install to Partition or Partitionless Disk =====
  
{{Note|{{ic|grub-bios}} (any version - including upstream Bazaar repo) does not encourage installation to a partition boot sector or a partitionless disk like GRUB Legacy or Syslinux does. This kind of setup is prone to breakage, especially during updates, and is not supported by Arch devs.}}
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{{Note|grub-bios does not encourage installation to a partition boot sector or a partitionless disk like GRUB Legacy or Syslinux does. This kind of setup is prone to breakage, especially during updates, and is not supported by Arch devs.}}
  
To set up {{ic|grub-bios}} to a partition boot sector, to a partitionless disk (also called superfloppy) or to a floppy disk, run (using for example {{ic|/dev/sdaX}} as the {{ic|/boot}} partition):
+
To set up grub-bios to a partition boot sector, to a partitionless disk (also called superfloppy) or to a floppy disk, run (using for example {{ic|/dev/sdaX}} as the {{ic|/boot}} partition):
 
   
 
   
 
  # modprobe dm-mod  
 
  # modprobe dm-mod  
 +
# grub-install --target=i386-pc --recheck --debug --force /dev/sdaX
 
  # chattr -i /boot/grub/i386-pc/core.img
 
  # chattr -i /boot/grub/i386-pc/core.img
# grub-install --target=i386-pc --recheck --debug --force /dev/sdaX
 
 
  # mkdir -p /boot/grub/locale
 
  # mkdir -p /boot/grub/locale
 
  # cp /usr/share/locale/en@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
 
  # cp /usr/share/locale/en@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
Line 183: Line 176:
 
  # cp /usr/share/locale/en@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
 
  # cp /usr/share/locale/en@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
  
You can then chainload GRUB2's {{ic|core.img}} from GRUB Legacy or syslinux as a Linux kernel or a multiboot kernel.
+
You can then chainload GRUB's {{ic|core.img}} from GRUB Legacy or syslinux as a Linux kernel or a multiboot kernel.
  
==== Generate GRUB2 BIOS Config file ====
+
==== Generate config file ====
  
Finally, generate a configuration for GRUB2 (this is explained in greater detail in the Configuration section):
+
Finally, generate a configuration for GRUB (this is explained in greater detail in the Configuration section):
  
 
  # grub-mkconfig -o /boot/grub/grub.cfg
 
  # grub-mkconfig -o /boot/grub/grub.cfg
Line 193: Line 186:
 
{{Note|The file path is {{ic|/boot/grub/grub.cfg}}, NOT {{ic|/boot/grub/i386-pc/grub.cfg}}.}}
 
{{Note|The file path is {{ic|/boot/grub/grub.cfg}}, NOT {{ic|/boot/grub/i386-pc/grub.cfg}}.}}
  
If grub(2) complains about "no suitable mode found" while booting, go to [[#Correct_GRUB2_No_Suitable_Mode_Found_Error]].
+
If GRUB complains about "no suitable mode found" while booting, go to [[#Correct No Suitable Mode Found Error]].
  
 
If {{ic|grub-mkconfig}} fails, convert your {{ic|/boot/grub/menu.lst}} file to {{ic|/boot/grub/grub.cfg}} using:
 
If {{ic|grub-mkconfig}} fails, convert your {{ic|/boot/grub/menu.lst}} file to {{ic|/boot/grub/grub.cfg}} using:
Line 234: Line 227:
 
</nowiki>}}
 
</nowiki>}}
  
If you forgot to create a GRUB2 {{ic|/boot/grub/grub.cfg}} config file and simply rebooted into GRUB2 Command Shell, type:
+
If you forgot to create a GRUB {{ic|/boot/grub/grub.cfg}} config file and simply rebooted into GRUB Command Shell, type:
  
 
  sh:grub> insmod legacycfg
 
  sh:grub> insmod legacycfg
 
  sh:grub> legacy_configfile ${prefix}/menu.lst
 
  sh:grub> legacy_configfile ${prefix}/menu.lst
  
Boot into Arch and re-create the proper GRUB2 {{ic|/boot/grub/grub.cfg}} config file.
+
Boot into Arch and re-create the proper GRUB {{ic|/boot/grub/grub.cfg}} config file.
  
 
{{Note|This option works only in BIOS systems, not in UEFI systems.}}
 
{{Note|This option works only in BIOS systems, not in UEFI systems.}}
  
==== Multiboot in BIOS ====
+
==== Multiboot ====
  
===== Boot Microsoft Windows installed in BIOS-MBR mode =====
+
===== Microsoft Windows installed in BIOS-MBR mode =====
  
{{Note|GRUB(2) supports booting {{ic|bootmgr}} directly and chainload of partition boot sector is no longer required to boot Windows in a BIOS-MBR setup.}}
+
{{Note|GRUB supports booting {{ic|bootmgr}} directly and chainload of partition boot sector is no longer required to boot Windows in a BIOS-MBR setup.}}
  
{{Warning|Take note that it is the SYSTEM PARTITION that has the bootmgr, not your "real" windows partition (C:), ie: when showing all UUID's with blkid it is the partition with LABEL&#61;"SYSTEM RESERVED" which is only about 100 mb big much like the boot partition for arch. See http://en.wikipedia.org/wiki/System_partition_and_boot_partition for some more info.}}
+
{{Warning|Take note that it is the '''system partition''' that has {{ic|bootmgr}}, not your "real" Windows partition (usually C:). When showing all UUIDs with blkid, the system partition is the one with {{ic|LABEL&#61;"SYSTEM RESERVED"}} and is only about 100 MB in size (much like the boot partition for Arch). See [[Wikipedia:System partition and boot partition]] for more info.}}
  
 
Find the UUID of the NTFS filesystem of the Windows's SYSTEM PARTITION where the {{ic|bootmgr}} and its files reside. For example, if Windows {{ic|bootmgr}} exists at {{ic|/media/SYSTEM_RESERVED/bootmgr}}:
 
Find the UUID of the NTFS filesystem of the Windows's SYSTEM PARTITION where the {{ic|bootmgr}} and its files reside. For example, if Windows {{ic|bootmgr}} exists at {{ic|/media/SYSTEM_RESERVED/bootmgr}}:
Line 260: Line 253:
 
  # grub-probe --target=hints_string /media/SYSTEM_RESERVED/bootmgr
 
  # grub-probe --target=hints_string /media/SYSTEM_RESERVED/bootmgr
 
  --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1
 
  --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1
 
{{Note|{{ic|grub-probe}} should be run as root.}}
 
  
 
{{Note|For Windows XP, replace {{ic|bootmgr}} with {{ic|ntldr}} in the above commands.}}
 
{{Note|For Windows XP, replace {{ic|bootmgr}} with {{ic|ntldr}} in the above commands.}}
Line 275: Line 266:
 
     insmod search_fs_uuid
 
     insmod search_fs_uuid
 
     insmod ntldr     
 
     insmod ntldr     
     search --fs-uuid --no-floppy --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE
+
     search --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE
 
     ntldr /bootmgr
 
     ntldr /bootmgr
 
}</pre>
 
}</pre>
Line 286: Line 277:
 
     insmod search_fs_uuid
 
     insmod search_fs_uuid
 
     insmod ntldr     
 
     insmod ntldr     
     search --fs-uuid --no-floppy --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE
+
     search --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE
 
     ntldr /ntldr
 
     ntldr /ntldr
 
  }
 
  }
  
=== UEFI systems ===
+
{{ic|/etc/grub.d/40_custom}} can be used as a template to create {{ic|/etc/grub.d/nn_custom}}. Where {{ic|nn}} defines the precendence, indicating the order the script is executed.  The order scripts are executed determine the placement in the grub boot menu.
  
{{Note|It is recommended to read the [[UEFI]], [[GPT]] and [[UEFI_Bootloaders]] pages before reading this part.}}
+
{{Note|{{ic|nn}} should be greater than 06 to ensure necessary scripts are executed first.}}
  
==== Hardware-Specific UEFI Examples ====
+
=== UEFI systems ===
 
+
It is well know that different motherboard manufactures implement UEFI differently.  Users experiencing problems getting Grub/EFI to work properly are encouraged to share detailed steps for hardware-specific cases where UEFI booting does not work as described below.  In an effort to keep the parent [[GRUB]] article neat and tidy, see the [[GRUB EFI Examples]] page for these special cases.
+
 
+
==== Install grub-uefi package ====
+
 
+
{{Note|Unless specified as EFI 1.x , EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware. Also unless stated explicitly, the instructions are general and not Mac specific. Some of them may not work or may be different in Macs. Apple's EFI implementation is neither a EFI 1.x version nor UEFI 2.x version but mixes up both. This kind of firmware does not fall under any one UEFI Specification version and is therefore not a standard UEFI firmware.}}
+
 
+
GRUB(2) UEFI bootloader is available in Arch Linux only from version 1.99~rc1. To install, first [[Unified_Extensible_Firmware_Interface#Detecting_UEFI_Firmware_Arch|detect which UEFI firmware arch]] you have (either x86_64 or i386).
+
 
+
Depending on that, install the appropriate package
+
  
For 64-bit aka x86_64 UEFI firmware:
+
{{Note|It is well know that different motherboard manufactures implement UEFI differently.  Users experiencing problems getting Grub/EFI to work properly are encouraged to share detailed steps for hardware-specific cases where UEFI booting does not work as described below. In an effort to keep the parent [[GRUB]] article neat and tidy, see the [[GRUB EFI Examples]] page for these special cases.}}
  # pacman -S grub-efi-x86_64
+
  
For 32-bit aka i386 UEFI firmware:
+
First [[Unified Extensible Firmware Interface#Detecting UEFI Firmware Arch|detect which UEFI firmware arch]] you have (either x86_64 or i386). Depending on the result, install the appropriate package:
# pacman -S grub-efi-i386
+
*For 64-bit aka x86_64 UEFI firmware, install {{Pkg|grub-efi-x86_64}}
 +
*For 32-bit aka i386 UEFI firmware, install {{Pkg|grub-efi-i386}}
  
{{Note|Simply installing the package will not update the {{ic|core.efi}} file and the GRUB(2) modules in the UEFI System Partition. You need to do this manually using {{ic|grub-install}} as explained below.}}
+
{{Note|Simply installing the package will not update the {{ic|core.efi}} file and the GRUB modules in the UEFI System Partition. You need to do this manually using {{ic|grub-install}} as explained below.}}
  
==== Install grub-uefi boot files ====
+
==== Install boot files ====
  
===== Install to UEFI SYSTEM PARTITION =====
+
===== Install to UEFI System Partition =====
  
 
{{Note|The below commands assume you are using {{ic|grub-efi-x86_64}} (for {{ic|grub-efi-i386}} replace {{ic|x86_64}} with {{ic|i386}} in the below commands).}}
 
{{Note|The below commands assume you are using {{ic|grub-efi-x86_64}} (for {{ic|grub-efi-i386}} replace {{ic|x86_64}} with {{ic|i386}} in the below commands).}}
  
{{Note|To do this, you need to boot using UEFI and not the BIOS. If you booted by just copying the ISO file to the USB drive, you will need to follow [[UEFI#Create_UEFI_bootable_USB_from_ISO|this guide]] or grub-install will show errors.}}
+
{{Note|To do this, you need to boot using UEFI and not the BIOS. If you booted by just copying the ISO file to the USB drive, you will need to follow [[Unified Extensible Firmware Interface#Create UEFI bootable USB from ISO|this guide]] or grub-install will show errors.}}
  
The UEFI system partition will need to be mounted at {{ic|/boot/efi/}} for the GRUB(2) install script to detect it:
+
The UEFI system partition will need to be mounted at {{ic|/boot/efi/}} for the GRUB install script to detect it:
  
 
  # mkdir -p /boot/efi
 
  # mkdir -p /boot/efi
Line 334: Line 315:
 
  # cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
 
  # cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
  
{{Note|Without {{ic|--target}} or {{ic|--directory}} option, grub-install cannot determine for which firmware grub(2) is being installed. In such cases grub-install will show {{ic|source_dir doesn't exist. Please specify --target or --directory}} message.}}
+
{{Note|Without {{ic|--target}} or {{ic|--directory}} option, grub-install cannot determine for which firmware GRUB is being installed. In such cases {{ic|grub-install}} will show {{ic|source_dir doesn't exist. Please specify --target or --directory}} message.}}
  
If you want to install grub(2) modules and {{ic|grub.cfg}} at the directory {{ic|/boot/efi/EFI/grub}} and the {{ic|grubx64.efi}} application at {{ic|/boot/efi/EFI/arch_grub}} (ie. all the grub(2) uefi files inside the UEFISYS partition itself) use:
+
If you want to install GRUB modules and {{ic|grub.cfg}} at the directory {{ic|/boot/efi/EFI/grub}} and the {{ic|grubx64.efi}} application at {{ic|/boot/efi/EFI/arch_grub}} (ie. all the GRUB UEFI files inside the UEFISYS partition itself) use:
  
 
  # modprobe dm-mod  
 
  # modprobe dm-mod  
Line 376: Line 357:
 
{{Note|In GRUB 2.00, the {{ic|grub-install}} option {{ic|--efi-directory}} replaces {{ic|--root-directory}} and the latter is deprecated.}}
 
{{Note|In GRUB 2.00, the {{ic|grub-install}} option {{ic|--efi-directory}} replaces {{ic|--root-directory}} and the latter is deprecated.}}
  
{{Note|The options {{ic|--efi-directory}} and {{ic|--bootloader-id}} are specific to GRUB(2) UEFI.}}
+
{{Note|The options {{ic|--efi-directory}} and {{ic|--bootloader-id}} are specific to GRUB UEFI.}}
 
   
 
   
 
In all the cases the UEFI SYSTEM PARTITION should be mounted for {{ic|grub-install}} to install {{ic|grubx64.efi}} in it, which will be launched by the firmware (using the {{ic|efibootmgr}} created boot entry in non-Mac systems).
 
In all the cases the UEFI SYSTEM PARTITION should be mounted for {{ic|grub-install}} to install {{ic|grubx64.efi}} in it, which will be launched by the firmware (using the {{ic|efibootmgr}} created boot entry in non-Mac systems).
  
If you notice carefully, there is no <device_path> option (Eg: {{ic|/dev/sda}}) at the end of the {{ic|grub-install}} command unlike the case of setting up GRUB(2) for BIOS systems. Any <device_path> provided will be ignored by the install script as UEFI bootloaders do not use MBR or Partition boot sectors at all.
+
If you notice carefully, there is no <device_path> option (Eg: {{ic|/dev/sda}}) at the end of the {{ic|grub-install}} command unlike the case of setting up GRUB for BIOS systems. Any <device_path> provided will be ignored by the install script as UEFI bootloaders do not use MBR or Partition boot sectors at all.
  
You may now be able to UEFI boot your system by creating a {{ic|grub.cfg}} file by following [[#Generate_GRUB2_UEFI_Config_file]] and [[#Create_GRUB2_entry_in_the_Firmware_Boot_Manager]].
+
You may now be able to UEFI boot your system by creating a {{ic|grub.cfg}} file by following [[#Generate UEFI Config file]] and [[#Create GRUB entry in the Firmware Boot Manager]].
  
==== Generate GRUB2 UEFI Config file ====
+
==== Generate config file ====
  
Finally, generate a configuration for GRUB(2) (this is explained in greater detail in the Configuration section):
+
Finally, generate a configuration for GRUB (this is explained in greater detail in the Configuration section):
  
 
  # grub-mkconfig -o <boot-directory>/grub/grub.cfg
 
  # grub-mkconfig -o <boot-directory>/grub/grub.cfg
Line 402: Line 383:
 
This is independent of the value of {{ic|--bootloader-id}} option.
 
This is independent of the value of {{ic|--bootloader-id}} option.
  
If GRUB2 complains about "no suitable mode found" while booting, try [[#Correct_GRUB2_No_Suitable_Mode_Found_Error]].
+
If GRUB complains about "no suitable mode found" while booting, try [[#Correct No Suitable Mode Found Error]].
  
==== Create GRUB2 Standalone UEFI Application ====
+
==== Create GRUB entry in the Firmware Boot Manager ====
  
It is possible to create a {{ic|grubx64_standalone.efi}} application which has all the modules embeddded in a memdisk within the uefi application, thus removing the need for having a separate directory populated with all the GRUB2 uefi modules and other related files. This is done using the {{ic|grub-mkstandalone}} command which is included in {{Pkg|grub-common}} >= 1:1.99-6 package.
+
{{ic|grub-install}} automatically tries to create a menu entry in the boot manager. If it doesn't, then see [[Beginners' Guide#GRUB]] for instructions to use {{ic|efibootmgr}} to create a menu entry. However, the problem is likely to be that you haven't booted your CD/USB in UEFI mode, as in [[Unified Extensible Firmware Interface#Create UEFI bootable USB from ISO]].
 +
 
 +
==== Create GRUB Standalone UEFI Application ====
 +
 
 +
It is possible to create a {{ic|grubx64_standalone.efi}} application which has all the modules embeddded in a memdisk within the UEFI application, thus removing the need for having a separate directory populated with all the GRUB UEFI modules and other related files. This is done using the {{ic|grub-mkstandalone}} command which is included in {{Pkg|grub-common}}.
  
 
The easiest way to do this would be with the install command already mentioned before, but specifying the modules to include. For example:
 
The easiest way to do this would be with the install command already mentioned before, but specifying the modules to include. For example:
Line 424: Line 409:
 
If you pass {{ic|/home/user/Desktop/grub.cfg}} the file will be included as {{ic|(memdisk)/home/user/Desktop/grub.cfg}}. If you pass {{ic|/home/user/Desktop/boot/grub/grub.cfg}} the file will be included as {{ic|(memdisk)/home/user/Desktop/boot/grub/grub.cfg}}. That is the reason for cd'ing into {{ic|/home/user/Desktop/boot/grub/}} and passing {{ic|boot/grub/grub.cfg}}, to include the file as {{ic|(memdisk)/boot/grub/grub.cfg}}, which is what {{ic|grub.efi}} expects the file to be.
 
If you pass {{ic|/home/user/Desktop/grub.cfg}} the file will be included as {{ic|(memdisk)/home/user/Desktop/grub.cfg}}. If you pass {{ic|/home/user/Desktop/boot/grub/grub.cfg}} the file will be included as {{ic|(memdisk)/home/user/Desktop/boot/grub/grub.cfg}}. That is the reason for cd'ing into {{ic|/home/user/Desktop/boot/grub/}} and passing {{ic|boot/grub/grub.cfg}}, to include the file as {{ic|(memdisk)/boot/grub/grub.cfg}}, which is what {{ic|grub.efi}} expects the file to be.
  
You need to create an UEFI Boot Manager entry for {{ic|/boot/efi/EFI/arch_grub/grubx64_standalone.efi}} using {{ic|efibootmgr}}. Follow [[#Create GRUB2 entry in the Firmware Boot Manager]].
+
You need to create an UEFI Boot Manager entry for {{ic|/boot/efi/EFI/arch_grub/grubx64_standalone.efi}} using {{ic|efibootmgr}}. Follow [[#Create GRUB entry in the Firmware Boot Manager]].
  
==== Multiboot in UEFI ====
+
==== Multiboot ====
  
===== Chainload Microsoft Windows x86_64 UEFI-GPT =====
+
===== Microsoft Windows installed in UEFI-GPT mode =====
  
 
Find the UUID of the FAT32 filesystem in the UEFI SYSTEM PARTITION where the Windows UEFI Bootloader files reside. For example, if Windows {{ic|bootmgfw.efi}} exists at {{ic|/boot/efi/EFI/Microsoft/Boot/bootmgfw.efi}} (ignore the upper-lower case differences since that is immaterial in FAT filesystem):
 
Find the UUID of the FAT32 filesystem in the UEFI SYSTEM PARTITION where the Windows UEFI Bootloader files reside. For example, if Windows {{ic|bootmgfw.efi}} exists at {{ic|/boot/efi/EFI/Microsoft/Boot/bootmgfw.efi}} (ignore the upper-lower case differences since that is immaterial in FAT filesystem):
Line 438: Line 423:
 
  --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1
 
  --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1
  
{{Note|{{ic|grub-probe}} should be run as root.}}
+
Then, add this code to {{ic|/etc/grub.d/40_custom}} to chainload Windows x86_64 (Vista SP1+, 7 or 8) installed in UEFI-GPT mode:
 
+
Then, add this code to {{ic|/boot/grub/grub.cfg}} OR {{ic|/boot/efi/EFI/grub/grub.cfg}} to chainload Windows x86_64 (Vista SP1+, 7 or 8) installed in UEFI-GPT mode:
+
  
 
  menuentry "Microsoft Windows Vista/7/8 x86_64 UEFI-GPT" {
 
  menuentry "Microsoft Windows Vista/7/8 x86_64 UEFI-GPT" {
Line 447: Line 430:
 
     insmod search_fs_uuid
 
     insmod search_fs_uuid
 
     insmod chain
 
     insmod chain
     search --fs-uuid --no-floppy --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1 1ce5-7f28
+
     search --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1 1ce5-7f28
 
     chainloader /efi/Microsoft/Boot/bootmgfw.efi
 
     chainloader /efi/Microsoft/Boot/bootmgfw.efi
 
  }
 
  }
 +
 +
Afterwards remake {{ic|/boot/grub/grub.cfg}}
 +
 +
# grub-mkconfig -o /boot/grub/grub.cfg
  
 
== Configuration ==
 
== Configuration ==
Line 455: Line 442:
 
You can also choose to automatically generate or manually edit {{ic|grub.cfg}}.
 
You can also choose to automatically generate or manually edit {{ic|grub.cfg}}.
  
{{Note|For EFI systems, if GRUB2 was installed with the {{ic|--boot-directory}} option set, the {{ic|grub.cfg}} file must be placed in the same directory as {{ic|grubx64.efi}}. Otherwise, the {{ic|grub.cfg}} file goes in {{ic|/boot/grub/}}, just like in the BIOS version of GRUB2.}}
+
{{Note|For EFI systems, if GRUB was installed with the {{ic|--boot-directory}} option set, the {{ic|grub.cfg}} file must be placed in the same directory as {{ic|grubx64.efi}}. Otherwise, the {{ic|grub.cfg}} file goes in {{ic|/boot/grub/}}, just like in GRUB BIOS.}}
  
{{Note|Here is a quite complete description of how to configure GRUB2: http://members.iinet.net/~herman546/p20/GRUB2%20Configuration%20File%20Commands.html }}
+
{{Note|Here is a quite complete description of how to configure GRUB: http://members.iinet.net/~herman546/p20/GRUB2%20Configuration%20File%20Commands.html }}
  
=== Automatically generating using grub-mkconfig (Recommended) ===
+
=== Automatically generating using grub-mkconfig ===
  
The GRUB2 {{ic|menu.lst}} equivalent configuration files are {{ic|/etc/default/grub}} and {{ic|/etc/grub.d/*}}. {{ic|grub-mkconfig}} uses these files to generate {{ic|grub.cfg}}. By default the script outputs to stdout. To generate a {{ic|grub.cfg}} file run the command:
+
The GRUB {{ic|menu.lst}} equivalent configuration files are {{ic|/etc/default/grub}} and {{ic|/etc/grub.d/*}}. {{ic|grub-mkconfig}} uses these files to generate {{ic|grub.cfg}}. By default the script outputs to stdout. To generate a {{ic|grub.cfg}} file run the command:
  
 
  # grub-mkconfig -o /boot/grub/grub.cfg
 
  # grub-mkconfig -o /boot/grub/grub.cfg
Line 496: Line 483:
 
|/boot/grub/grub.cfg
 
|/boot/grub/grub.cfg
 
|<nowiki>
 
|<nowiki>
# Config file for GRUB2 - The GNU GRand Unified Bootloader
+
# Config file for GRUB - The GNU GRand Unified Bootloader
 
# /boot/grub/grub.cfg
 
# /boot/grub/grub.cfg
  
Line 531: Line 518:
 
=== Dual-booting ===
 
=== Dual-booting ===
  
{{Note|If you want GRUB2 to automatically search for other systems, you may wish to install {{Pkg|os-prober}}.}}
+
{{Note|If you want GRUB to automatically search for other systems, you may wish to install {{Pkg|os-prober}}.}}
  
 
==== Using grub-mkconfig ====
 
==== Using grub-mkconfig ====
Line 574: Line 561:
 
==== With Windows via EasyBCD and NeoGRUB ====
 
==== With Windows via EasyBCD and NeoGRUB ====
  
Since EasyBCD's NeoGRUB currently does not understand the GRUB2 menu format, chainload to it by replacing the contents of your {{ic|C:\NST\menu.lst}} file with lines similar to the following:
+
Since EasyBCD's NeoGRUB currently does not understand the GRUB menu format, chainload to it by replacing the contents of your {{ic|C:\NST\menu.lst}} file with lines similar to the following:
  
 
  default 0
 
  default 0
Line 585: Line 572:
 
===Visual Configuration===
 
===Visual Configuration===
  
In GRUB2 it is possible, by default, to change the look of the menu. Make sure to initialize, if not done already, GRUB2 graphical terminal, gfxterm, with proper video mode, gfxmode, in GRUB2. This can be seen in the section [[#Correct_GRUB2_No_Suitable_Mode_Found_Error]]. This video mode is passed by GRUB2 to the linux kernel via 'gfxpayload' so any visual configurations need this mode in order to be in effect.
+
In GRUB it is possible, by default, to change the look of the menu. Make sure to initialize, if not done already, GRUB graphical terminal, gfxterm, with proper video mode, gfxmode, in GRUB. This can be seen in the section [[#Correct No Suitable Mode Found Error]]. This video mode is passed by GRUB to the linux kernel via 'gfxpayload' so any visual configurations need this mode in order to be in effect.
  
 
====Setting the framebuffer resolution ====
 
====Setting the framebuffer resolution ====
  
GRUB2 can set the framebuffer for both GRUB2 itself and the kernel. The old {{ic|1=vga=}} way is deprecated. The preferred method is editing {{ic|/etc/default/grub}} as the following sample:
+
GRUB can set the framebuffer for both GRUB itself and the kernel. The old {{ic|1=vga=}} way is deprecated. The preferred method is editing {{ic|/etc/default/grub}} as the following sample:
  
 
  GRUB_GFXMODE=1024x768x32
 
  GRUB_GFXMODE=1024x768x32
Line 595: Line 582:
  
 
To generate the changes, run:  
 
To generate the changes, run:  
  grub-mkconfig -o /boot/grub/grub.cfg
+
  # grub-mkconfig -o /boot/grub/grub.cfg
  
 
The {{ic|gfxpayload}} property will make sure the kernel keeps the resolution.
 
The {{ic|gfxpayload}} property will make sure the kernel keeps the resolution.
  
 
{{Note|If this example does not work for you try to replace {{ic|1=gfxmode="1024x768x32"}} by {{ic|1=vbemode="0x105"}}. Remember to replace the specified resolution with one suitable for your screen.}}
 
{{Note|If this example does not work for you try to replace {{ic|1=gfxmode="1024x768x32"}} by {{ic|1=vbemode="0x105"}}. Remember to replace the specified resolution with one suitable for your screen.}}
{{Note|To show all the modes you can use {{ic|1=# hwinfo --framebuffer}} (hwinfo is available in [community]), while at GRUB2 prompt you can use the {{ic|1=vbeinfo}} command.}}
+
{{Note|To show all the modes you can use {{ic|1=# hwinfo --framebuffer}} (hwinfo is available in [community]), while at GRUB prompt you can use the {{ic|1=vbeinfo}} command.}}
  
 
If this method does not work for you, the deprecated {{ic|1=vga=}} method will still work. Just
 
If this method does not work for you, the deprecated {{ic|1=vga=}} method will still work. Just
Line 612: Line 599:
 
Some times for Intel graphic adapters neither {{ic|1=# hwinfo --framebuffer}} nor {{ic|1=vbeinfo}} will show you the desired resolution. In this case you can use {{ic|915resolution}} hack. This hack will temporarily modify video BIOS and add needed resolution. See [http://915resolution.mango-lang.org/ 915resolution's home page]
 
Some times for Intel graphic adapters neither {{ic|1=# hwinfo --framebuffer}} nor {{ic|1=vbeinfo}} will show you the desired resolution. In this case you can use {{ic|915resolution}} hack. This hack will temporarily modify video BIOS and add needed resolution. See [http://915resolution.mango-lang.org/ 915resolution's home page]
  
In the following I will proceed with the example for my system. Please adjust the recipe for your needs. First you need to find a video mode which will be modified later. For that, run {{ic|915resolution}} in GRUB2 command shell:
+
In the following I will proceed with the example for my system. Please adjust the recipe for your needs. First you need to find a video mode which will be modified later. For that, run {{ic|915resolution}} in GRUB command shell:
 
  915resolution -l
 
  915resolution -l
 
The output will be something like:
 
The output will be something like:
Line 621: Line 608:
 
Next, our purpose is to overwrite mode 30. (You can choose what ever mode you want.) In the file {{ic|/etc/grub.d/00_header}} just before the {{ic|set gfxmode&#61;${GRUB_GFXMODE}}} line insert:
 
Next, our purpose is to overwrite mode 30. (You can choose what ever mode you want.) In the file {{ic|/etc/grub.d/00_header}} just before the {{ic|set gfxmode&#61;${GRUB_GFXMODE}}} line insert:
 
  915resolution 30 1440 900
 
  915resolution 30 1440 900
Here we are overwriting the mode {{ic|30}} with {{ic|1440x900}} resolution. Lastly we need to set {{ic|GRUB_GFXMODE}} as described earlier, regenerate GRUB2 configuration file and reboot to test changes:
+
Here we are overwriting the mode {{ic|30}} with {{ic|1440x900}} resolution. Lastly we need to set {{ic|GRUB_GFXMODE}} as described earlier, regenerate GRUB configuration file and reboot to test changes:
 
  # grub-mkconfig -o /boot/grub/grub.cfg
 
  # grub-mkconfig -o /boot/grub/grub.cfg
 
  # reboot
 
  # reboot
Line 627: Line 614:
 
====Background image and bitmap fonts====
 
====Background image and bitmap fonts====
  
GRUB2 comes with support for background images and bitmap fonts in {{ic|pf2}} format. The unifont font is included in the {{Pkg|grub-common}} package under the filename {{ic|unicode.pf2}}, or, as only ASCII characters under the name {{ic|ascii.pf2}}.
+
GRUB comes with support for background images and bitmap fonts in {{ic|pf2}} format. The unifont font is included in the {{Pkg|grub-common}} package under the filename {{ic|unicode.pf2}}, or, as only ASCII characters under the name {{ic|ascii.pf2}}.
  
 
Image formats supported include tga, png and jpeg, providing the correct modules are loaded. The maximum supported resolution depends on your hardware.
 
Image formats supported include tga, png and jpeg, providing the correct modules are loaded. The maximum supported resolution depends on your hardware.
  
Make sure you have set up the proper [https://wiki.archlinux.org/index.php/GRUB2#Setting_the_framebuffer_resolution framebuffer resolution].
+
Make sure you have set up the proper [[#Setting the framebuffer resolution|framebuffer resolution]].
  
 
Edit {{ic|/etc/default/grub}} like this:
 
Edit {{ic|/etc/default/grub}} like this:
Line 655: Line 642:
 
====Theme====
 
====Theme====
  
Here is an example for configuring Starfield theme which was included in GRUB2 package.
+
Here is an example for configuring Starfield theme which was included in GRUB package.
  
 
Edit {{ic|/etc/default/grub}}
 
Edit {{ic|/etc/default/grub}}
Line 668: Line 655:
 
====Menu colors====
 
====Menu colors====
  
You can set the menu colors in GRUB2. The available colors for GRUB2 are at https://www.gnu.org/software/grub/manual/html_node/Theme-file-format.html#Theme-file-format.
+
You can set the menu colors in GRUB. The available colors for GRUB can be found in [https://www.gnu.org/software/grub/manual/html_node/Theme-file-format.html the GRUB Manual].
 
Here is an example:
 
Here is an example:
  
Line 680: Line 667:
 
====Hidden menu====
 
====Hidden menu====
  
One of the unique features of GRUB2 is hiding/skipping the menu and showing it by holding {{keypress|Esc}} when needed. You can also adjust whether you want to see the timeout counter.
+
One of the unique features of GRUB is hiding/skipping the menu and showing it by holding {{keypress|Esc}} when needed. You can also adjust whether you want to see the timeout counter.
  
 
Edit {{ic|/etc/default/grub}} as you wish. Here is an example where the comments from the beginning of the two lines have been removed to enable the feature, the timeout has been set to five seconds and to be shown to the user:
 
Edit {{ic|/etc/default/grub}} as you wish. Here is an example where the comments from the beginning of the two lines have been removed to enable the feature, the timeout has been set to five seconds and to be shown to the user:
Line 687: Line 674:
  
 
and run:
 
and run:
  grub-mkconfig -o /boot/grub/grub.cfg
+
  # grub-mkconfig -o /boot/grub/grub.cfg
  
 
====Disable framebuffer====
 
====Disable framebuffer====
  
Users who use NVIDIA proprietary driver might wish to disable GRUB2's framebuffer as it can cause problems with the binary driver.
+
Users who use NVIDIA proprietary driver might wish to disable GRUB's framebuffer as it can cause problems with the binary driver.
  
 
To disable framebuffer, edit {{ic|/etc/default/grub}} and uncomment the following line:
 
To disable framebuffer, edit {{ic|/etc/default/grub}} and uncomment the following line:
Line 698: Line 685:
 
and run:
 
and run:
 
  grub-mkconfig -o /boot/grub/grub.cfg
 
  grub-mkconfig -o /boot/grub/grub.cfg
 +
 +
Another option if you want to keep the framebuffer in GRUB is to revert to text mode just before starting the kernel. To do that modify the variable in {{ic|/etc/default/grub}}:
 +
GRUB_GFXPAYLOAD_LINUX=text
 +
 +
and rebuild the configuration as before.
  
 
=== Other Options ===
 
=== Other Options ===
Line 724: Line 716:
 
==== RAID ====
 
==== RAID ====
  
GRUB2 provides convenient handling of RAID volumes. You need to add {{ic|insmod mdraid}} which allows you to address the volume natively. For example, {{ic|/dev/md0}} becomes:
+
GRUB provides convenient handling of RAID volumes. You need to add {{ic|insmod mdraid}} which allows you to address the volume natively. For example, {{ic|/dev/md0}} becomes:
 
  set root=(md0)
 
  set root=(md0)
  
Line 733: Line 725:
 
One naming scheme for [[Persistent block device naming]] is the use of globally unique UUIDs to detect partitions instead of the "old" {{ic|/dev/sd*}}. Advantages are covered up in the above linked article.  
 
One naming scheme for [[Persistent block device naming]] is the use of globally unique UUIDs to detect partitions instead of the "old" {{ic|/dev/sd*}}. Advantages are covered up in the above linked article.  
  
Persistent naming via filesystem UUIDs are used by default in GRUB2.  
+
Persistent naming via filesystem UUIDs are used by default in GRUB.  
  
 
{{Note|The {{ic|/boot/grub.cfg}} file needs regeneration with the new UUID in {{ic|/etc/default/grub}} every time a relevant filesystem is resized or recreated. Remember this when modifying partitions & filesystems with a Live-CD.}}
 
{{Note|The {{ic|/boot/grub.cfg}} file needs regeneration with the new UUID in {{ic|/etc/default/grub}} every time a relevant filesystem is resized or recreated. Remember this when modifying partitions & filesystems with a Live-CD.}}
Line 752: Line 744:
  
 
  menuentry "Arch Linux, session texte" {
 
  menuentry "Arch Linux, session texte" {
     search --label --no-floppy --set=root archroot
+
     search --label --set=root archroot
 
     linux /boot/vmlinuz-linux root=/dev/disk/by-label/archroot ro
 
     linux /boot/vmlinuz-linux root=/dev/disk/by-label/archroot ro
 
     initrd /boot/initramfs-linux.img
 
     initrd /boot/initramfs-linux.img
Line 759: Line 751:
 
==== Recall previous entry ====
 
==== Recall previous entry ====
  
GRUB2 can remember the last entry you booted from and use this as the default entry to boot from next time. This is useful if you have multiple kernels (i.e., the current Arch one and the LTS kernel as a fallback option) or operating systems. To do this, edit {{ic|/etc/default/grub}} and change the setting of {{ic|GRUB_DEFAULT}}:
+
GRUB can remember the last entry you booted from and use this as the default entry to boot from next time. This is useful if you have multiple kernels (i.e., the current Arch one and the LTS kernel as a fallback option) or operating systems. To do this, edit {{ic|/etc/default/grub}} and change the setting of {{ic|GRUB_DEFAULT}}:
  
 
  GRUB_DEFAULT=saved
 
  GRUB_DEFAULT=saved
Line 771: Line 763:
 
==== Security ====
 
==== Security ====
  
If you want to secure GRUB2 so it is not possible for anyone to change boot parameters or use the command line, you can add a user/password combination to GRUB2's configuration files. To do this, run the command {{ic|grub-mkpasswd-pbkdf2}}. Enter a password and confirm it. The output will look like this:
+
If you want to secure GRUB so it is not possible for anyone to change boot parameters or use the command line, you can add a user/password combination to GRUB's configuration files. To do this, run the command {{ic|grub-mkpasswd-pbkdf2}}. Enter a password and confirm it. The output will look like this:
  
 
{{bc|<nowiki>
 
{{bc|<nowiki>
Line 783: Line 775:
 
where {{ic|<password>}} is the string generated by {{ic|grub-mkpasswd_pbkdf2}}.
 
where {{ic|<password>}} is the string generated by {{ic|grub-mkpasswd_pbkdf2}}.
  
Regenerate your configuration file. Your GRUB2 command line, boot parameters and all boot entries are now protected.
+
Regenerate your configuration file. Your GRUB command line, boot parameters and all boot entries are now protected.
  
 
This can be relaxed and further customized with more users as described in the "Security" part of [https://www.gnu.org/software/grub/manual/grub.html#Security the GRUB manual].
 
This can be relaxed and further customized with more users as described in the "Security" part of [https://www.gnu.org/software/grub/manual/grub.html#Security the GRUB manual].
Line 789: Line 781:
 
==== Root Encryption ====
 
==== Root Encryption ====
  
To let GRUB2 automatically add the kernel parameters for root encryption,
+
To let GRUB automatically add the kernel parameters for root encryption,
 
add {{ic|1=cryptdevice=/dev/yourdevice:label}} to {{ic|GRUB_CMDLINE_LINUX}} in {{ic|/etc/default/grub}}.
 
add {{ic|1=cryptdevice=/dev/yourdevice:label}} to {{ic|GRUB_CMDLINE_LINUX}} in {{ic|/etc/default/grub}}.
  
Line 802: Line 794:
 
Regenerate the configuration.
 
Regenerate the configuration.
  
=== Booting an ISO Directly From GRUB2 ===
+
==== Boot non-default entry only once ====
 +
 
 +
The command {{ic|grub-reboot}} is very helpful to boot another entry than the default only once. GRUB loads the entry passed in the first command line argument, when the system is rebooted the next time. Most importantly GRUB returns to loading the default entry for all future booting. Changing the configuration file or selecting an entry in the GRUB menu is not necessary.
 +
 
 +
=== Booting an ISO Directly From GRUB ===
 
Edit {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} to add an entry for the target ISO. When finished, update the GRUB menu as with the usual {{ic|grub-mkconfig -o /boot/grub/grub.cfg}} (as root).
 
Edit {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} to add an entry for the target ISO. When finished, update the GRUB menu as with the usual {{ic|grub-mkconfig -o /boot/grub/grub.cfg}} (as root).
  
 
==== Arch ISO ====
 
==== Arch ISO ====
{{Note|Be sure to adjust the {{ic|hdX,Y}} in the third line to point to the correct disk/partition number of the isofile. Also adjust the {{ic|img_dev}} line to match this same location. However, if booting the ISO from USB on a computer which also has one internal HDD, then it needs to be {{ic|hd0,Y}} with {{ic|sdbY}}, instead of {{ic|sdaY}}.}}
+
{{Note|The example assumes that the iso is in {{ic|/archives}} on {{ic|hd0,6}}. Users must adjust the location and hdd/partition in ALL of the lines below to match their systems. However, if booting the ISO from USB on a computer which also has one internal HDD, then it needs to be {{ic|hd0,Y}} with {{ic|sdbY}}, instead of {{ic|sdaY}}.}}
  
  menuentry "Archlinux-2011.08.19-netinstall-x86_64.iso" {
+
'''Example using x86_64'''
    set isofile="/archives/archlinux-2011.08.19-netinstall-x86_64.iso"
+
  menuentry "Archlinux-2013.01.04-dual.iso" --class iso {
    loopback loop (hd0,7)$isofile
+
  set isofile="/archives/archlinux-2013.01.04-dual.iso"
    linux (loop)/arch/boot/x86_64/vmlinuz archisolabel=ARCH_201108 img_dev=/dev/sda7 img_loop=$isofile earlymodules=loop
+
  loopback loop (hd0,6)$isofile
    initrd (loop)/arch/boot/x86_64/archiso.img
+
  linux (loop)/arch/boot/x86_64/vmlinuz archisolabel=ARCH_201301 img_dev=/dev/sda6 img_loop=$isofile earlymodules=loop
 +
  initrd (loop)/arch/boot/x86_64/archiso.img
 
  }
 
  }
  
  menuentry "Archlinux-2012.07.15-netinstall-dual.iso" {
+
'''Example using i686'''
    set isofile="/archives/archlinux-2012.07.15-netinstall-dual.iso"
+
  menuentry "Archlinux-2013.01.04-dual.iso" --class iso {
    loopback loop (hd0,7)$isofile
+
  set isofile="/archives/archlinux-2013.01.04-dual.iso"
    linux (loop)/arch/boot/x86_64/vmlinuz archisolabel=ARCH_201207 img_dev=/dev/sda7 img_loop=$isofile
+
  loopback loop (hd0,6)$isofile
    initrd (loop)/arch/boot/x86_64/archiso.img
+
  linux (loop)/arch/boot/i686/vmlinuz archisolabel=ARCH_201301 img_dev=/dev/sda6 img_loop=$isofile earlymodules=loop
 +
  initrd (loop)/arch/boot/i686/archiso.img
 
  }
 
  }
  
Line 825: Line 823:
  
 
==== Ubuntu ISO ====
 
==== Ubuntu ISO ====
{{Note|Be sure to adjust the {{ic|hdX,Y}} in the third line to point to the correct disk or partition number of the ISO file.}}
+
{{Note|The example assumes that the iso is in {{ic|/archives}} on {{ic|hd0,6}}. Users must adjust the location and hdd/partition in the lines below to match their systems.}}
 +
 
 +
menuentry "ubuntu-13.04-desktop-amd64.iso" {
 +
    set isofile="/archives/ubuntu-13.04-desktop-amd64.iso"
 +
    loopback loop (hd0,6)$isofile
 +
    linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=$isofile quiet noeject noprompt splash --
 +
    initrd (loop)/casper/initrd.lz
 +
}
  
 
  menuentry "ubuntu-12.04-desktop-amd64.iso" {
 
  menuentry "ubuntu-12.04-desktop-amd64.iso" {
     set isofile="/path/to/ubuntu-12.04-desktop-amd64.iso"
+
     set isofile="/archives/ubuntu-12.04-desktop-amd64.iso"
     loopback loop (hdX,Y)$isofile
+
     loopback loop (hd0,6)$isofile
 
     linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile quiet noeject noprompt splash --
 
     linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile quiet noeject noprompt splash --
 
     initrd (loop)/casper/initrd.lz
 
     initrd (loop)/casper/initrd.lz
Line 840: Line 845:
 
== Using the command shell ==
 
== Using the command shell ==
  
Since the MBR is too small to store all GRUB2 modules, only the menu and a few basic commands reside there. The majority of GRUB2 functionality remains in modules in {{ic|/boot/grub}}, which are inserted as needed. In error conditions (e.g. if the partition layout changes) GRUB2 may fail to boot. When this happens, a command shell may appear.
+
Since the MBR is too small to store all GRUB modules, only the menu and a few basic commands reside there. The majority of GRUB functionality remains in modules in {{ic|/boot/grub}}, which are inserted as needed. In error conditions (e.g. if the partition layout changes) GRUB may fail to boot. When this happens, a command shell may appear.
  
GRUB2 offers multiple shells/prompts. If there is a problem reading the menu but the bootloader is able to find the disk, you will likely be dropped to the "normal" shell:
+
GRUB offers multiple shells/prompts. If there is a problem reading the menu but the bootloader is able to find the disk, you will likely be dropped to the "normal" shell:
 
  sh:grub>
 
  sh:grub>
  
Line 855: Line 860:
 
=== Pager support ===
 
=== Pager support ===
  
GRUB2 supports pager for reading commands that provide long output (like the help command). This works only in normal shell mode and not in rescue mode. To enable pager, in GRUB2 command shell type:
+
GRUB supports pager for reading commands that provide long output (like the help command). This works only in normal shell mode and not in rescue mode. To enable pager, in GRUB command shell type:
 
  sh:grub> set pager=1
 
  sh:grub> set pager=1
  
Line 861: Line 866:
  
 
Following package may be installed from [[AUR]]
 
Following package may be installed from [[AUR]]
* [https://aur.archlinux.org/packages.php?ID=44020 grub-customizer] (requires gettext gksu gtkmm hicolor-icon-theme openssl)
+
* {{aur|grub-customizer}} (requires gettext gksu gtkmm hicolor-icon-theme openssl)
*:Customize the bootloader (GRUB2 or BURG)
+
*:Customize the bootloader (GRUB or BURG)
* [http://kde-apps.org/content/show.php?content=139643 grub2-editor] (requires kdelibs)
+
* {{aur|grub2-editor}} (requires kdelibs)
*:A KDE4 control module for configuring the GRUB2 bootloader
+
*:A KDE4 control module for configuring the GRUB bootloader
* [http://kde-apps.org/content/show.php?content=137886 kcm-grub2] (requires kdelibs python2-qt kdebindings-python)
+
* {{aur|kcm-grub2}} (requires kdelibs python2-qt kdebindings-python)
*:This Kcm module manages the most common settings of Grub2.
+
*:This Kcm module manages the most common settings of GRUB.
* [http://sourceforge.net/projects/startup-manager/ startupmanager] (requires gnome-python imagemagick yelp python2 xorg-xrandr)
+
* {{aur|startupmanager}} (requires gnome-python imagemagick yelp python2 xorg-xrandr)
*:GUI app for changing the settings of GRUB, GRUB2, Usplash and Splashy
+
*:GUI app for changing the settings of GRUB Legacy, GRUB, Usplash and Splashy
  
 
== parttool for hide/unhide ==
 
== parttool for hide/unhide ==
Line 910: Line 915:
 
  boot
 
  boot
  
After successfully booting the Arch Linux installation, users can correct {{ic|grub.cfg}} as needed and then reinstall GRUB2.
+
After successfully booting the Arch Linux installation, users can correct {{ic|grub.cfg}} as needed and then reinstall GRUB.
  
to reinstall GRUB2 and fix the problem completely, changing {{ic|/dev/sda}} if needed. See [[#Bootloader installation]] for details.
+
To reinstall GRUB and fix the problem completely, changing {{ic|/dev/sda}} if needed. See [[#Bootloader installation]] for details.
  
 
== Combining the use of UUIDs and basic scripting ==
 
== Combining the use of UUIDs and basic scripting ==
Line 926: Line 931:
 
      
 
      
 
       # Get the boot/root devices and set them in the root and grub_boot variables
 
       # Get the boot/root devices and set them in the root and grub_boot variables
       search --fs-uuid --no-floppy --set=root $the_root_uuid
+
       search --fs-uuid --set=root $the_root_uuid
       search --fs-uuid --no-floppy --set=grub_boot $the_boot_uuid
+
       search --fs-uuid --set=grub_boot $the_boot_uuid
 
      
 
      
 
       # Check to see if boot and root are equal.
 
       # Check to see if boot and root are equal.
Line 944: Line 949:
 
Any troubleshooting should be added here.
 
Any troubleshooting should be added here.
  
=== Enable GRUB2 debug messages ===
+
=== Intel BIOS not booting GPT ===
 +
 
 +
Some Intel BIOS's require at least one bootable MBR partition to be present at boot, causing GPT-partitioned boot setups to be unbootable.
 +
 
 +
This can be circumvented by using (for instance) fdisk to mark one of the GPT partitions (preferably the 1007KiB partition you've created for GRUB already) bootable in the MBR. This can be achieved, using fdisk, by the following commands: Start fdisk against the disk you're installing, for instance "fdisk /dev/sda", then press "a" and select the partition you wish to mark as bootable (probably #1) by pressing the corresponding number, finally press "w" to write the changes to the MBR.
 +
 
 +
Note that the bootable-marking must be done in fdisk or similar, not in GParted or others, as they will not set the bootable flag in the MBR.
 +
 
 +
More information is available [http://www.rodsbooks.com/gdisk/bios.html here]
 +
 
 +
=== Enable debug messages ===
  
 
Add:
 
Add:
Line 953: Line 968:
 
to {{ic|grub.cfg}}.
 
to {{ic|grub.cfg}}.
  
=== Correct GRUB2 No Suitable Mode Found Error ===
+
=== Correct No Suitable Mode Found Error ===
  
 
If you get this error when booting any menuentry:
 
If you get this error when booting any menuentry:
Line 960: Line 975:
 
  Booting however
 
  Booting however
  
Then you need to initialize GRUB2 graphical terminal ({{ic|gfxterm}}) with proper video mode ({{ic|gfxmode}}) in GRUB2. This video mode is passed by GRUB2 to the linux kernel via 'gfxpayload'. In case of UEFI systems, if the GRUB2 video mode is not initialized, no kernel boot messages will be shown in the terminal (atleast until KMS kicks in).
+
Then you need to initialize GRUB graphical terminal ({{ic|gfxterm}}) with proper video mode ({{ic|gfxmode}}) in GRUB. This video mode is passed by GRUB to the linux kernel via 'gfxpayload'. In case of UEFI systems, if the GRUB video mode is not initialized, no kernel boot messages will be shown in the terminal (atleast until KMS kicks in).
  
Copy {{ic|/usr/share/grub/unicode.pf2}} to ${GRUB2_PREFIX_DIR} ({{ic|/boot/grub/}} in case of BIOS and UEFI systems). If GRUB2 UEFI was installed with {{ic|1=--boot-directory=/boot/efi/EFI}} set, then the directory is {{ic|/boot/efi/EFI/grub/}}:
+
Copy {{ic|/usr/share/grub/unicode.pf2}} to ${GRUB_PREFIX_DIR} ({{ic|/boot/grub/}} in case of BIOS and UEFI systems). If GRUB UEFI was installed with {{ic|1=--boot-directory=/boot/efi/EFI}} set, then the directory is {{ic|/boot/efi/EFI/grub/}}:
  
  # cp /usr/share/grub/unicode.pf2 ${GRUB2_PREFIX_DIR}
+
  # cp /usr/share/grub/unicode.pf2 ${GRUB_PREFIX_DIR}
  
If {{ic|/usr/share/grub/unicode.pf2}} does not exist, install {{Pkg|bdf-unifont}}, create the {{ic|unifont.pf2}} file and then copy it to {{ic|${GRUB2_PREFIX_DIR<nowiki>}</nowiki>}}:
+
If {{ic|/usr/share/grub/unicode.pf2}} does not exist, install {{Pkg|bdf-unifont}}, create the {{ic|unifont.pf2}} file and then copy it to {{ic|${GRUB_PREFIX_DIR<nowiki>}</nowiki>}}:
  
 
  # grub-mkfont -o unicode.pf2 /usr/share/fonts/misc/unifont.bdf
 
  # grub-mkfont -o unicode.pf2 /usr/share/fonts/misc/unifont.bdf
  
Then, in the {{ic|grub.cfg}} file, add the following lines to enable GRUB2 to pass the video mode correctly to the kernel, without of which you will only get a black screen (no output) but booting (actually) proceeds successfully without any system hang.
+
Then, in the {{ic|grub.cfg}} file, add the following lines to enable GRUB to pass the video mode correctly to the kernel, without of which you will only get a black screen (no output) but booting (actually) proceeds successfully without any system hang.
  
 
BIOS systems:
 
BIOS systems:
Line 993: Line 1,008:
 
  fi
 
  fi
  
As you can see for gfxterm (graphical terminal) to function properly, {{ic|unicode.pf2}} font file should exist in {{ic|${GRUB2_PREFIX_DIR<nowiki>}</nowiki>}}.
+
As you can see for gfxterm (graphical terminal) to function properly, {{ic|unicode.pf2}} font file should exist in {{ic|${GRUB_PREFIX_DIR<nowiki>}</nowiki>}}.
  
 
=== msdos-style error message ===
 
=== msdos-style error message ===
Line 1,002: Line 1,017:
 
  grub-setup: error: If you really want blocklists, use --force.
 
  grub-setup: error: If you really want blocklists, use --force.
  
This error may occur when you try installing GRUB2 in a VMware container. Read more about it [https://bbs.archlinux.org/viewtopic.php?pid=581760#p581760 here]. It happens when the first partition starts just after the MBR (block 63), without the usual space of 1 MiB (2048 blocks) before the first partition. Read [[#MBR_aka_msdos_partitioning_specific_instructions]]
+
This error may occur when you try installing GRUB in a VMware container. Read more about it [https://bbs.archlinux.org/viewtopic.php?pid=581760#p581760 here]. It happens when the first partition starts just after the MBR (block 63), without the usual space of 1 MiB (2048 blocks) before the first partition. Read [[#Master Boot Record (MBR) specific instructions]]
  
=== UEFI GRUB2 drops to shell ===
+
=== GRUB UEFI drops to shell ===
  
If GRUB loads but drops you into the rescue shell with no errors, it may be because of a missing or misplaced {{ic|grub.cfg}}. This will happen if GRUB2 UEFI was installed with {{ic|--boot-directory}} and {{ic|grub.cfg}} is missing OR if the partition number of the boot partition changed (which is hard-coded into the {{ic|grubx64.efi}} file).
+
If GRUB loads but drops you into the rescue shell with no errors, it may be because of a missing or misplaced {{ic|grub.cfg}}. This will happen if GRUB UEFI was installed with {{ic|--boot-directory}} and {{ic|grub.cfg}} is missing OR if the partition number of the boot partition changed (which is hard-coded into the {{ic|grubx64.efi}} file).
  
=== UEFI GRUB2 not loaded ===
+
=== GRUB UEFI not loaded ===
 
In some cases the EFI may fail to load GRUB correctly. Provided everything is set up correctly, the output of:
 
In some cases the EFI may fail to load GRUB correctly. Provided everything is set up correctly, the output of:
 
  efibootmgr -v
 
  efibootmgr -v
Line 1,030: Line 1,045:
  
 
=== Boot freezes ===
 
=== Boot freezes ===
If booting gets stuck without any error message after grub2 loading the kernel and the initial ramdisk, try removing the {{ic|add_efi_memmap}} kernel parameter.
+
If booting gets stuck without any error message after GRUB loading the kernel and the initial ramdisk, try removing the {{ic|add_efi_memmap}} kernel parameter.
  
 
=== Restore GRUB Legacy ===
 
=== Restore GRUB Legacy ===
Line 1,054: Line 1,069:
 
== References ==
 
== References ==
  
# Official GRUB2 Manual - https://www.gnu.org/software/grub/manual/grub.html
+
# Official GRUB Manual - https://www.gnu.org/software/grub/manual/grub.html
# Ubuntu wiki page for GRUB2 - https://help.ubuntu.com/community/Grub2
+
# Ubuntu wiki page for GRUB - https://help.ubuntu.com/community/Grub2
# GRUB2 wiki page describing steps to compile for UEFI systems - https://help.ubuntu.com/community/UEFIBooting
+
# GRUB wiki page describing steps to compile for UEFI systems - https://help.ubuntu.com/community/UEFIBooting
 
# Wikipedia's page on [[Wikipedia:BIOS Boot partition|BIOS Boot partition]]
 
# Wikipedia's page on [[Wikipedia:BIOS Boot partition|BIOS Boot partition]]
  
 
== External Links ==
 
== External Links ==
  
# [https://github.com/the-ridikulus-rat/My_Shell_Scripts/blob/master/grub/grub_bios.sh A Linux Bash Shell script to compile and install GRUB(2) for BIOS from BZR Source]
+
# [https://github.com/the-ridikulus-rat/My_Shell_Scripts/blob/master/grub/grub_bios.sh A Linux Bash Shell script to compile and install GRUB for BIOS from BZR Source]
# [https://github.com/the-ridikulus-rat/My_Shell_Scripts/blob/master/grub/grub_uefi.sh A Linux Bash Shell script to compile and install GRUB(2) for UEFI from BZR Source]
+
# [https://github.com/the-ridikulus-rat/My_Shell_Scripts/blob/master/grub/grub_uefi.sh A Linux Bash Shell script to compile and install GRUB for UEFI from BZR Source]

Revision as of 15:11, 29 April 2013

Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary text Template:Article summary heading Template:Article summary wiki - BURG is a brand-new boot loader based on GRUB2. It can be built on a wider range of OS, and has a highly configurable menu system which works in both text and graphic mode. Template:Article summary wiki - previous Version, now obsolete. Template:Article summary heading Template:Article summary wiki Template:Article summary link Template:Article summary end GRUB - not to be confused with GRUB Legacy - is the next generation of the GRand Unified Bootloader. GRUB is derived from PUPA which was a research project to develop the next generation of what is now GRUB Legacy. GRUB has been rewritten from scratch to clean up everything and provide modularity and portability [1].

In brief, the bootloader is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the Linux kernel. The kernel, in turn, initializes the rest of the operating system.

Contents

Preface

  • The name GRUB officially refers to version 2 of the software, see [2]. If you are looking for the article on the legacy version, see GRUB Legacy.
  • GRUB supports Btrfs as root (without a separate /boot filesystem) compressed with either zlib or LZO.

Notes for current GRUB Legacy users

  • Upgrade from GRUB Legacy to GRUB is the much same as fresh installing GRUB which is covered below.
  • There are differences in the commands of GRUB Legacy and GRUB. Familiarize yourself with GRUB commands before proceeding (e.g. "find" has been replaced with "search").
  • GRUB is now modular and no longer requires "stage 1.5". As a result, the bootloader itself is limited -- modules are loaded from the hard drive as needed to expand functionality (e.g. for LVM or RAID support).
  • Device naming has changed between GRUB Legacy and GRUB. Partitions are numbered from 1 instead of 0 while drives are still numbered from 0, and prefixed with partition-table type. For example, /dev/sda1 would be referred to as (hd0,msdos1) (for MBR) or (hd0,gpt1) (for GPT).

Backup Important Data

Although a GRUB installation should run smoothly, it is strongly recommended to keep the GRUB Legacy files before upgrading to GRUB2.

# mv /boot/grub /boot/grub-legacy

Backup the MBR which contains the boot code and partition table (Replace /dev/sdX with your actual disk path)

# dd if=/dev/sdX of=/path/to/backup/mbr_backup bs=512 count=1

Only 446 bytes of the MBR contain boot code, the next 64 contain the partition table. If you do not want to overwrite your partition table when restoring, it is strongly advised to backup only the MBR boot code:

# dd if=/dev/sdX of=/path/to/backup/bootcode_backup bs=446 count=1

If unable to install GRUB2 correctly, see #Restore GRUB Legacy.

Preliminary Requirements

BIOS systems

GUID Partition Table (GPT) specific instructions

GRUB in BIOS-GPT configuration requires a BIOS Boot Partition to embed its core.img in the absence of post-MBR gap in GPT partitioned systems (which is taken over by the GPT Primary Header and Primary Partition table). This partition is used by GRUB only in BIOS-GPT setups. No such partition type exists in case of MBR partitioning (at least not for GRUB). This partition is also not required if the system is UEFI based, as no embedding of bootsectors takes place in that case.

For a BIOS-GPT configuration, create a 1007 KiB partition at the beginning of the disk using cgdisk or GNU Parted with no filesystem. The size of 1007 KiB will allow for the following partition to be correctly alligned at 1024 KiB. If needed, the partition can also be located somewhere else on the disk, but it should be within the first 2 TiB region. Set the partition type to 0xEF02 in gdisk, EF02 in cgdisk or set <BOOT_PART_NUM> bios_grub on in GNU Parted.

Note: This partition should be created before grub-install or grub-setup is run.
Note: gdisk will only allow you to create this partition on the position which will waste the least amount of space (sector 34-2047) if you create it last, after all the other partitions. This is because gdisk will auto-align partitions to 2048-sector boundaries if possible.
Master Boot Record (MBR) specific instructions

Usually the post-MBR gap (after the 512 byte MBR region and before the start of the 1st partition) in many MBR (or msdos disklabel) partitioned systems is 31 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 to 2 MiB is recommended to provide sufficient room for embedding GRUB's core.img (FS#24103). It is advisable to use a partitioner which supports 1 MiB partition alignment to obtain this space as well as satisfy other non-512 byte sector issues (which are unrelated to embedding of core.img).

MBR partitioning has better support than GPT partitioning in some operating systems, such as older versions of Microsoft Windows (up to Windows 7) and Haiku. If you dual boot such an operating system, consider using MBR partitioning.

A MBR disk may be convertible to GPT if there is a small amount of extra space available. See GUID Partition Table#Convert from MBR to GPT.

UEFI systems

Note: It is recommended to read and understand the UEFI, GPT and UEFI Bootloaders pages.
Create and Mount the UEFI System Partition

Follow Unified Extensible Firmware Interface#EFI System Partition for instructions on creating a UEFI System Partition. Then mount the UEFI System Partition at /boot/efi. If you have mounted the UEFI System Partition at some other mountpoint, replace /boot/efi in the below instructions with that mountpoint:

# mkdir -p /boot/efi
# mount -t vfat <UEFI_SYSTEM_PARTITION> /boot/efi

Create a /boot/efi/EFI directory:

# mkdir /boot/efi/EFI

Installation

BIOS systems

GRUB can be installed with the grub-bios package from the official repositories. It will replace grub-legacy or grub, if it is installed.

Note: Simply installing the package won't update the /boot/grub/i386-pc/core.img file and the GRUB modules in /boot/grub/i386-pc. You need to update them manually using grub-install as explained below.

Install boot files

There are 3 ways to install GRUB boot files in BIOS booting:

Install to GPT BIOS Boot Partition

GUID Partition Table disks do not have a reserved "boot track". Therefore you must create a BIOS Boot Partition (0xEF02) to hold the GRUB core image.

Using GNU Parted, you can set this using a command such as the following:

# parted /dev/disk set <partition-number> bios_grub on

If you are using gdisk, set the partition type to 0xEF02. With partitioning programs that require setting the GUID directly, it should be ‘21686148-6449-6e6f-744e656564454649’ (stored on disk as "!haHdInotNeedEFI" if interpreted as ASCII).

Warning: Be very careful which partition you select when marking it as a BIOS Boot Partition. When GRUB finds a BIOS Boot Partition during installation, it will automatically overwrite part of it. Make sure that the partition does not contain any other data.

To setup grub-bios on a GPT disk, populate the /boot/grub directory, generate the /boot/grub/i386-pc/core.img file, and embed it in the BIOS Boot Partition, run:

# modprobe dm-mod
# grub-install --target=i386-pc --recheck --debug /dev/sda
# mkdir -p /boot/grub/locale
# cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo

where /dev/sda is the destination of the installation.

Install to 440-byte MBR boot code region

To setup grub-bios in the 440-byte Master Boot Record boot code region, populate the /boot/grub directory, generate the /boot/grub/i386-pc/core.img file, embed it in the 31 KiB (minimum size - varies depending on partition alignment) post-MBR gap, and generate the configuration file, run:

# modprobe dm-mod
# grub-install --recheck /dev/sda
# grub-mkconfig -o /boot/grub/grub.cfg

where /dev/sda is the destination of the installation (in this case the MBR of the first SATA disk). If you use LVM for your /boot, you can install GRUB on multiple physical disks.

Warning: Make sure to check the /boot directory if you use the latter. Sometimes the boot-directory parameter creates another /boot folder inside of /boot. A wrong install would look like: /boot/boot/grub/.
Install to Partition or Partitionless Disk
Note: grub-bios does not encourage installation to a partition boot sector or a partitionless disk like GRUB Legacy or Syslinux does. This kind of setup is prone to breakage, especially during updates, and is not supported by Arch devs.

To set up grub-bios to a partition boot sector, to a partitionless disk (also called superfloppy) or to a floppy disk, run (using for example /dev/sdaX as the /boot partition):

# modprobe dm-mod 
# grub-install --target=i386-pc --recheck --debug --force /dev/sdaX
# chattr -i /boot/grub/i386-pc/core.img
# mkdir -p /boot/grub/locale
# cp /usr/share/locale/en@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
# chattr +i /boot/grub/i386-pc/core.img

You need to use the --force option to allow usage of blocklists and should not use --grub-setup=/bin/true (which is similar to simply generating core.img).

grub-install will give out warnings like which should give you the idea of what might go wrong with this approach:

/sbin/grub-setup: warn: Attempting to install GRUB to a partitionless disk or to a partition. This is a BAD idea.
/sbin/grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists. 
                        However, blocklists are UNRELIABLE and their use is discouraged.

Without --force you may get the below error and grub-setup will not setup its boot code in the partition boot sector:

/sbin/grub-setup: error: will not proceed with blocklists

With --force you should get:

Installation finished. No error reported.

The reason why grub-setup does not by default allow this is because in case of partition or a partitionless disk is that grub-bios relies on embedded blocklists in the partition bootsector to locate the /boot/grub/i386-pc/core.img file and the prefix dir /boot/grub. The sector locations of core.img may change whenever the filesystem in the partition is being altered (files copied, deleted etc.). For more info see https://bugzilla.redhat.com/show_bug.cgi?id=728742 and https://bugzilla.redhat.com/show_bug.cgi?id=730915.

The workaround for this is to set the immutable flag on /boot/grub/i386-pc/core.img (using chattr command as mentioned above) so that the sector locations of the core.img file in the disk is not altered. The immutable flag on /boot/grub/i386-pc/core.img needs to be set only if grub-bios is installed to a partition boot sector or a partitionless disk, not in case of installation to MBR or simple generation of core.img without embedding any bootsector (mentioned above).

Generate core.img alone

To populate the /boot/grub directory and generate a /boot/grub/i386-pc/core.img file without embedding any grub-bios bootsector code in the MBR, post-MBR region, or the partition bootsector, add --grub-setup=/bin/true to grub-install:

# modprobe dm-mod
# grub-install --target=i386-pc --grub-setup=/bin/true --recheck --debug /dev/sda
# mkdir -p /boot/grub/locale
# cp /usr/share/locale/en@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo

You can then chainload GRUB's core.img from GRUB Legacy or syslinux as a Linux kernel or a multiboot kernel.

Generate config file

Finally, generate a configuration for GRUB (this is explained in greater detail in the Configuration section):

# grub-mkconfig -o /boot/grub/grub.cfg
Note: The file path is /boot/grub/grub.cfg, NOT /boot/grub/i386-pc/grub.cfg.

If GRUB complains about "no suitable mode found" while booting, go to #Correct No Suitable Mode Found Error.

If grub-mkconfig fails, convert your /boot/grub/menu.lst file to /boot/grub/grub.cfg using:

# grub-menulst2cfg /boot/grub/menu.lst /boot/grub/grub.cfg

For example:

/boot/grub/menu.lst
default=0
timeout=5

title  Arch Linux Stock Kernel
root   (hd0,0)
kernel /vmlinuz-linux root=/dev/sda2 ro
initrd /initramfs-linux.img

title  Arch Linux Stock Kernel Fallback
root   (hd0,0)
kernel /vmlinuz-linux root=/dev/sda2 ro
initrd /initramfs-linux-fallback.img
/boot/grub/grub.cfg
set default='0'; if [ x"$default" = xsaved ]; then load_env; set default="$saved_entry"; fi
set timeout=5

menuentry 'Arch Linux Stock Kernel' {
  set root='(hd0,1)'; set legacy_hdbias='0'
  legacy_kernel   '/vmlinuz-linux' '/vmlinuz-linux' 'root=/dev/sda2' 'ro'
  legacy_initrd '/initramfs-linux.img' '/initramfs-linux.img'
  
}

menuentry 'Arch Linux Stock Kernel Fallback' {
  set root='(hd0,1)'; set legacy_hdbias='0'
  legacy_kernel   '/vmlinuz-linux' '/vmlinuz-linux' 'root=/dev/sda2' 'ro'
  legacy_initrd '/initramfs-linux-fallback.img' '/initramfs-linux-fallback.img'
}

If you forgot to create a GRUB /boot/grub/grub.cfg config file and simply rebooted into GRUB Command Shell, type:

sh:grub> insmod legacycfg
sh:grub> legacy_configfile ${prefix}/menu.lst

Boot into Arch and re-create the proper GRUB /boot/grub/grub.cfg config file.

Note: This option works only in BIOS systems, not in UEFI systems.

Multiboot

Microsoft Windows installed in BIOS-MBR mode
Note: GRUB supports booting bootmgr directly and chainload of partition boot sector is no longer required to boot Windows in a BIOS-MBR setup.
Warning: Take note that it is the system partition that has bootmgr, not your "real" Windows partition (usually C:). When showing all UUIDs with blkid, the system partition is the one with LABEL="SYSTEM RESERVED" and is only about 100 MB in size (much like the boot partition for Arch). See Wikipedia:System partition and boot partition for more info.

Find the UUID of the NTFS filesystem of the Windows's SYSTEM PARTITION where the bootmgr and its files reside. For example, if Windows bootmgr exists at /media/SYSTEM_RESERVED/bootmgr:

For Windows Vista/7/8:

# grub-probe --target=fs_uuid /media/SYSTEM_RESERVED/bootmgr
69B235F6749E84CE
# grub-probe --target=hints_string /media/SYSTEM_RESERVED/bootmgr
--hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1
Note: For Windows XP, replace bootmgr with ntldr in the above commands.

Then, add the below code to /etc/grub.d/40_custom or /boot/grub/custom.cfg and regenerate grub.cfg with grub-mkconfig as explained above to boot Windows (XP, Vista, 7 or 8) installed in BIOS-MBR mode:

For Windows Vista/7/8:

menuentry "Microsoft Windows Vista/7/8 BIOS-MBR" {
    insmod part_msdos
    insmod ntfs
    insmod search_fs_uuid
    insmod ntldr     
    search --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE
    ntldr /bootmgr
}

For Windows XP:

menuentry "Microsoft Windows XP" {
    insmod part_msdos
    insmod ntfs
    insmod search_fs_uuid
    insmod ntldr     
    search --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE
    ntldr /ntldr
}

/etc/grub.d/40_custom can be used as a template to create /etc/grub.d/nn_custom. Where nn defines the precendence, indicating the order the script is executed. The order scripts are executed determine the placement in the grub boot menu.

Note: nn should be greater than 06 to ensure necessary scripts are executed first.

UEFI systems

Note: It is well know that different motherboard manufactures implement UEFI differently. Users experiencing problems getting Grub/EFI to work properly are encouraged to share detailed steps for hardware-specific cases where UEFI booting does not work as described below. In an effort to keep the parent GRUB article neat and tidy, see the GRUB EFI Examples page for these special cases.

First detect which UEFI firmware arch you have (either x86_64 or i386). Depending on the result, install the appropriate package:

Note: Simply installing the package will not update the core.efi file and the GRUB modules in the UEFI System Partition. You need to do this manually using grub-install as explained below.

Install boot files

Install to UEFI System Partition
Note: The below commands assume you are using grub-efi-x86_64 (for grub-efi-i386 replace x86_64 with i386 in the below commands).
Note: To do this, you need to boot using UEFI and not the BIOS. If you booted by just copying the ISO file to the USB drive, you will need to follow this guide or grub-install will show errors.

The UEFI system partition will need to be mounted at /boot/efi/ for the GRUB install script to detect it:

# mkdir -p /boot/efi
# mount -t vfat /dev/sdXY /boot/efi

Install GRUB UEFI application to /boot/efi/EFI/arch_grub and its modules to /boot/grub/x86_64-efi (recommended) using:

# modprobe dm-mod
# grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=arch_grub --recheck --debug
# mkdir -p /boot/grub/locale
# cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
Note: Without --target or --directory option, grub-install cannot determine for which firmware GRUB is being installed. In such cases grub-install will show source_dir doesn't exist. Please specify --target or --directory message.

If you want to install GRUB modules and grub.cfg at the directory /boot/efi/EFI/grub and the grubx64.efi application at /boot/efi/EFI/arch_grub (ie. all the GRUB UEFI files inside the UEFISYS partition itself) use:

# modprobe dm-mod 
# grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=arch_grub --boot-directory=/boot/efi/EFI --recheck --debug
# mkdir -p /boot/efi/EFI/grub/locale
# cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/efi/EFI/grub/locale/en.mo

The --efi-directory option mentions the mountpoint of UEFI SYSTEM PARTITION , --bootloader-id mentions the name of the directory used to store the grubx64.efi file and --boot-directory mentions the directory wherein the actual modules will be installed (and into which grub.cfg should be created).

The actual paths are:

<efi-directory>/<EFI or efi>/<bootloader-id>/grubx64.efi
<boot-directory>/grub/x86_64-efi/<all modules, grub.efi, core.efi, grub.cfg>
Note: the --bootloader-id option does not change <boot-directory>/grub, i.e. you cannot install the modules to <boot-directory>/<bootloader-id>, the path is hard-coded to be <boot-directory>/grub.

In --efi-directory=/boot/efi --boot-directory=/boot/efi/EFI --bootloader-id=grub:

<efi-directory>/<EFI or efi>/<bootloader-id> == <boot-directory>/grub == /boot/efi/EFI/grub

In --efi-directory=/boot/efi --boot-directory=/boot/efi/EFI --bootloader-id=arch_grub:

<efi-directory>/<EFI or efi>/<bootloader-id> == /boot/efi/EFI/arch_grub
<boot-directory>/grub == /boot/efi/EFI/grub

In --efi-directory=/boot/efi --boot-directory=/boot --bootloader-id=arch_grub:

<efi-directory>/<EFI or efi>/<bootloader-id> == /boot/efi/EFI/arch_grub
<boot-directory>/grub == /boot/grub

In --efi-directory=/boot/efi --boot-directory=/boot --bootloader-id=grub:

<efi-directory>/<EFI or efi>/<bootloader-id> == /boot/efi/EFI/grub
<boot-directory>/grub == /boot/grub

The <efi-directory>/<EFI or efi>/<bootloader-id>/grubx64.efi is an exact copy of <boot-directory>/grub/x86_64-efi/core.efi.

Note: In GRUB 2.00, the grub-install option --efi-directory replaces --root-directory and the latter is deprecated.
Note: The options --efi-directory and --bootloader-id are specific to GRUB UEFI.

In all the cases the UEFI SYSTEM PARTITION should be mounted for grub-install to install grubx64.efi in it, which will be launched by the firmware (using the efibootmgr created boot entry in non-Mac systems).

If you notice carefully, there is no <device_path> option (Eg: /dev/sda) at the end of the grub-install command unlike the case of setting up GRUB for BIOS systems. Any <device_path> provided will be ignored by the install script as UEFI bootloaders do not use MBR or Partition boot sectors at all.

You may now be able to UEFI boot your system by creating a grub.cfg file by following #Generate UEFI Config file and #Create GRUB entry in the Firmware Boot Manager.

Generate config file

Finally, generate a configuration for GRUB (this is explained in greater detail in the Configuration section):

# grub-mkconfig -o <boot-directory>/grub/grub.cfg
Note: The file path is <boot-directory>/grub/grub.cfg, NOT <boot-directory>/grub/x86_64-efi/grub.cfg.

If you used --boot-directory=/boot:

# grub-mkconfig -o /boot/grub/grub.cfg

If you used --boot-directory=/boot/efi/EFI:

# grub-mkconfig -o /boot/efi/EFI/grub/grub.cfg

This is independent of the value of --bootloader-id option.

If GRUB complains about "no suitable mode found" while booting, try #Correct No Suitable Mode Found Error.

Create GRUB entry in the Firmware Boot Manager

grub-install automatically tries to create a menu entry in the boot manager. If it doesn't, then see Beginners' Guide#GRUB for instructions to use efibootmgr to create a menu entry. However, the problem is likely to be that you haven't booted your CD/USB in UEFI mode, as in Unified Extensible Firmware Interface#Create UEFI bootable USB from ISO.

Create GRUB Standalone UEFI Application

It is possible to create a grubx64_standalone.efi application which has all the modules embeddded in a memdisk within the UEFI application, thus removing the need for having a separate directory populated with all the GRUB UEFI modules and other related files. This is done using the grub-mkstandalone command which is included in grub-common.

The easiest way to do this would be with the install command already mentioned before, but specifying the modules to include. For example:

# grub-mkstandalone --directory="/usr/lib/grub/x86_64-efi/" --format="x86_64-efi" --compression="xz" \
--output="/boot/efi/EFI/arch_grub/grubx64_standalone.efi" <any extra files you want to include>

The grubx64_standalone.efi file expects grub.cfg to be within its $prefix which is (memdisk)/boot/grub. The memdisk is embedded within the efi app. The grub-mkstandlone script allow passing files to be included in the memdisk image to be as the arguments to the script (in <any extra files you want to include>).

If you have the grub.cfg at /home/user/Desktop/grub.cfg, then create a temporary /home/user/Desktop/boot/grub/ directory, copy the /home/user/Desktop/grub.cfg to /home/user/Desktop/boot/grub/grub.cfg, cd into /home/user/Desktop/boot/grub/ and run:

# grub-mkstandalone --directory="/usr/lib/grub/x86_64-efi/" --format="x86_64-efi" --compression="xz" \
--output="/boot/efi/EFI/arch_grub/grubx64_standalone.efi" "boot/grub/grub.cfg"

The reason to cd into /home/user/Desktop/boot/grub/ and to pass the file path as boot/grub/grub.cfg (notice the lack of a leading slash - boot/ vs /boot/ ) is because dir1/dir2/file is included as (memdisk)/dir1/dir2/file by the grub-mkstandalone script.

If you pass /home/user/Desktop/grub.cfg the file will be included as (memdisk)/home/user/Desktop/grub.cfg. If you pass /home/user/Desktop/boot/grub/grub.cfg the file will be included as (memdisk)/home/user/Desktop/boot/grub/grub.cfg. That is the reason for cd'ing into /home/user/Desktop/boot/grub/ and passing boot/grub/grub.cfg, to include the file as (memdisk)/boot/grub/grub.cfg, which is what grub.efi expects the file to be.

You need to create an UEFI Boot Manager entry for /boot/efi/EFI/arch_grub/grubx64_standalone.efi using efibootmgr. Follow #Create GRUB entry in the Firmware Boot Manager.

Multiboot

Microsoft Windows installed in UEFI-GPT mode

Find the UUID of the FAT32 filesystem in the UEFI SYSTEM PARTITION where the Windows UEFI Bootloader files reside. For example, if Windows bootmgfw.efi exists at /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi (ignore the upper-lower case differences since that is immaterial in FAT filesystem):

# grub-probe --target=fs_uuid /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi
1ce5-7f28
# grub-probe --target=hints_string /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi
--hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1

Then, add this code to /etc/grub.d/40_custom to chainload Windows x86_64 (Vista SP1+, 7 or 8) installed in UEFI-GPT mode:

menuentry "Microsoft Windows Vista/7/8 x86_64 UEFI-GPT" {
    insmod part_gpt
    insmod fat
    insmod search_fs_uuid
    insmod chain
    search --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1 1ce5-7f28
    chainloader /efi/Microsoft/Boot/bootmgfw.efi
}

Afterwards remake /boot/grub/grub.cfg

# grub-mkconfig -o /boot/grub/grub.cfg

Configuration

You can also choose to automatically generate or manually edit grub.cfg.

Note: For EFI systems, if GRUB was installed with the --boot-directory option set, the grub.cfg file must be placed in the same directory as grubx64.efi. Otherwise, the grub.cfg file goes in /boot/grub/, just like in GRUB BIOS.
Note: Here is a quite complete description of how to configure GRUB: http://members.iinet.net/~herman546/p20/GRUB2%20Configuration%20File%20Commands.html

Automatically generating using grub-mkconfig

The GRUB menu.lst equivalent configuration files are /etc/default/grub and /etc/grub.d/*. grub-mkconfig uses these files to generate grub.cfg. By default the script outputs to stdout. To generate a grub.cfg file run the command:

# grub-mkconfig -o /boot/grub/grub.cfg

/etc/grub.d/10_linux is set to automatically add menu items for Arch linux that work out of the box, to any generated configuration. Other operating systems may need to be added manually to /etc/grub.d/40_custom or /boot/grub/custom.cfg

Additional arguments

To pass custom additional arguments to the Linux image, you can set the GRUB_CMDLINE_LINUX variable in /etc/default/grub.

For example, use GRUB_CMDLINE_LINUX="resume=/dev/sdaX" where sdaX is your swap partition to enable resume after hibernation.

You can also use GRUB_CMDLINE_LINUX="resume=/dev/disk/by-uuid/${swap_uuid}", where ${swap_uuid} is the UUID of your swap partition.

Multiple entries are separated by spaces within the double quotes. So, for users who want both resume and systemd it would look like this: GRUB_CMDLINE_LINUX="resume=/dev/sdaX init=/usr/lib/systemd/systemd"

See Kernel parameters for more info.

Manually creating grub.cfg

Warning: Editing this file is strongly not recommended. The file is generated by the grub-mkconfig command, and it is best to edit your /etc/default/grub or one of the scripts in the /etc/grub.d folder.

A basic GRUB config file uses the following options

  • (hdX,Y) is the partition Y on disk X, partition numbers starting at 1, disk numbers starting at 0
  • set default=N is the default boot entry that is chosen after timeout for user action
  • set timeout=M is the time M to wait in seconds for a user selection before default is booted
  • menuentry "title" {entry options} is a boot entry titled title
  • set root=(hdX,Y) sets the boot partition, where the kernel and GRUB modules are stored (boot need not be a separate partition, and may simply be a directory under the "root" partition (/)

An example configuration:

/boot/grub/grub.cfg
# Config file for GRUB - The GNU GRand Unified Bootloader
# /boot/grub/grub.cfg

# DEVICE NAME CONVERSIONS
#
#  Linux           Grub
# -------------------------
#  /dev/fd0        (fd0)
#  /dev/sda        (hd0)
#  /dev/sdb2       (hd1,2)
#  /dev/sda3       (hd0,3)
#

# Timeout for menu
set timeout=5

# Set default boot entry as Entry 0
set default=0

# (0) Arch Linux
menuentry "Arch Linux" {
    set root=(hd0,1)
    linux /vmlinuz-linux root=/dev/sda3 ro
    initrd /initramfs-linux.img
}

## (1) Windows
#menuentry "Windows" {
#set root=(hd0,3)
#chainloader +1
#}

Dual-booting

Note: If you want GRUB to automatically search for other systems, you may wish to install os-prober.

Using grub-mkconfig

The best way to add other entries is editing the /etc/grub.d/40_custom or /boot/grub/custom.cfg . The entries in this file will be automatically added when running grub-mkconfig. After adding the new lines, run:

# grub-mkconfig -o /boot/grub/grub.cfg 

to generate an updated grub.cfg.

With GNU/Linux

Assuming that the other distro is on partition sda2:

menuentry "Other Linux" {
set root=(hd0,2)
linux /boot/vmlinuz (add other options here as required)
initrd /boot/initrd.img (if the other kernel uses/needs one)
}
With FreeBSD

Requires that FreeBSD is installed on a single partition with UFS. Assuming it is installed on sda4:

menuentry "FreeBSD" {
set root=(hd0,4)
chainloader +1
}
With Windows

This assumes that your Windows partition is sda3. Remember you need to point set root and chainloader to the system reserve partition that windows made when it installed, not the actual partition windows is on. This example works if your system reserve partition is sda3.

# (2) Windows XP
menuentry "Windows XP" {
    set root=(hd0,3)
    chainloader (hd0,3)+1
}

If the Windows bootloader is on an entirely different hard drive than GRUB, it may be necessary to trick Windows into believing that it is the first hard drive. This was possible with drivemap. Assuming GRUB is on hd0 and Windows is on hd2, you need to add the following after set root:

drivemap -s hd0 hd2

With Windows via EasyBCD and NeoGRUB

Since EasyBCD's NeoGRUB currently does not understand the GRUB menu format, chainload to it by replacing the contents of your C:\NST\menu.lst file with lines similar to the following:

default 0
timeout 1
title       Chainload into GRUB v2
root        (hd0,7)
kernel      /boot/grub/i386-pc/core.img

Visual Configuration

In GRUB it is possible, by default, to change the look of the menu. Make sure to initialize, if not done already, GRUB graphical terminal, gfxterm, with proper video mode, gfxmode, in GRUB. This can be seen in the section #Correct No Suitable Mode Found Error. This video mode is passed by GRUB to the linux kernel via 'gfxpayload' so any visual configurations need this mode in order to be in effect.

Setting the framebuffer resolution

GRUB can set the framebuffer for both GRUB itself and the kernel. The old vga= way is deprecated. The preferred method is editing /etc/default/grub as the following sample:

GRUB_GFXMODE=1024x768x32
GRUB_GFXPAYLOAD_LINUX=keep

To generate the changes, run:

# grub-mkconfig -o /boot/grub/grub.cfg

The gfxpayload property will make sure the kernel keeps the resolution.

Note: If this example does not work for you try to replace gfxmode="1024x768x32" by vbemode="0x105". Remember to replace the specified resolution with one suitable for your screen.
Note: To show all the modes you can use # hwinfo --framebuffer (hwinfo is available in [community]), while at GRUB prompt you can use the vbeinfo command.

If this method does not work for you, the deprecated vga= method will still work. Just add it next to the "GRUB_CMDLINE_LINUX_DEFAULT=" line in /etc/default/grub for eg: "GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=792" will give you a 1024x768 resolution.

You can choose one of these resolutions: 640×480, 800×600, 1024×768, 1280×1024, 1600×1200, 1920×1200

915resolution hack

Some times for Intel graphic adapters neither # hwinfo --framebuffer nor vbeinfo will show you the desired resolution. In this case you can use 915resolution hack. This hack will temporarily modify video BIOS and add needed resolution. See 915resolution's home page

In the following I will proceed with the example for my system. Please adjust the recipe for your needs. First you need to find a video mode which will be modified later. For that, run 915resolution in GRUB command shell:

915resolution -l

The output will be something like:

Intel 800/900 Series VBIOS Hack : version 0.5.3
...
Mode 30 : 640x480, 8 bits/pixel
...

Next, our purpose is to overwrite mode 30. (You can choose what ever mode you want.) In the file /etc/grub.d/00_header just before the set gfxmode=${GRUB_GFXMODE} line insert:

915resolution 30 1440 900

Here we are overwriting the mode 30 with 1440x900 resolution. Lastly we need to set GRUB_GFXMODE as described earlier, regenerate GRUB configuration file and reboot to test changes:

# grub-mkconfig -o /boot/grub/grub.cfg
# reboot

Background image and bitmap fonts

GRUB comes with support for background images and bitmap fonts in pf2 format. The unifont font is included in the grub-common package under the filename unicode.pf2, or, as only ASCII characters under the name ascii.pf2.

Image formats supported include tga, png and jpeg, providing the correct modules are loaded. The maximum supported resolution depends on your hardware.

Make sure you have set up the proper framebuffer resolution.

Edit /etc/default/grub like this:

GRUB_BACKGROUND="/boot/grub/myimage"
#GRUB_THEME="/path/to/gfxtheme"
GRUB_FONT="/path/to/font.pf2"
Note: If you have installed GRUB on a separate partition, /boot/grub/myimage becomes /grub/myimage.

To generate the changes and add the information into grub.cfg, run:

grub-mkconfig -o /boot/grub/grub.cfg

If adding the splash image was successful, the user will see "Found background image..." in the terminal as the command is executed. If this phrase is not seen, the image information was probably not incorporated into the grub.cfg file.

If the image is not displayed, check:

  • The path and the filename in /etc/default/grub are correct.
  • The image is of the proper size and format (tga, png, 8-bit jpg).
  • The image was saved in the RGB mode, and is not indexed.
  • The console mode is not enabled in /etc/default/grub.
  • The command grub-mkconfig must be executed to place the background image information into the /boot/grub/grub.cfg file.

Theme

Here is an example for configuring Starfield theme which was included in GRUB package.

Edit /etc/default/grub

GRUB_THEME="/usr/share/grub/themes/starfield/theme.txt"

Generate the changes:

grub-mkconfig -o /boot/grub/grub.cfg

If configuring the theme was successful, you'll see Found theme: /usr/share/grub/themes/starfield/theme.txt in the terminal. Your splash image will usually not be displayed when using a theme.

Menu colors

You can set the menu colors in GRUB. The available colors for GRUB can be found in the GRUB Manual. Here is an example:

Edit /etc/default/grub:

GRUB_COLOR_NORMAL="light-blue/black"
GRUB_COLOR_HIGHLIGHT="light-cyan/blue"

Generate the changes:

grub-mkconfig -o /boot/grub/grub.cfg

Hidden menu

One of the unique features of GRUB is hiding/skipping the menu and showing it by holding Template:Keypress when needed. You can also adjust whether you want to see the timeout counter.

Edit /etc/default/grub as you wish. Here is an example where the comments from the beginning of the two lines have been removed to enable the feature, the timeout has been set to five seconds and to be shown to the user:

GRUB_HIDDEN_TIMEOUT=5
GRUB_HIDDEN_TIMEOUT_QUIET=false

and run:

# grub-mkconfig -o /boot/grub/grub.cfg

Disable framebuffer

Users who use NVIDIA proprietary driver might wish to disable GRUB's framebuffer as it can cause problems with the binary driver.

To disable framebuffer, edit /etc/default/grub and uncomment the following line:

GRUB_TERMINAL_OUTPUT=console

and run:

grub-mkconfig -o /boot/grub/grub.cfg

Another option if you want to keep the framebuffer in GRUB is to revert to text mode just before starting the kernel. To do that modify the variable in /etc/default/grub:

GRUB_GFXPAYLOAD_LINUX=text

and rebuild the configuration as before.

Other Options

LVM

If you use LVM for your /boot, add the following before menuentry lines:

insmod lvm

and specify your root in the menuentry as:

set root=lvm/lvm_group_name-lvm_logical_boot_partition_name

Example:

# (0) Arch Linux
menuentry "Arch Linux" {
insmod lvm
set root=lvm/VolumeGroup-lv_boot
# you can only set following two lines
linux /vmlinuz-linux root=/dev/mapper/VolumeGroup-root ro
initrd /initramfs-linux.img
}

RAID

GRUB provides convenient handling of RAID volumes. You need to add insmod mdraid which allows you to address the volume natively. For example, /dev/md0 becomes:

set root=(md0)

whereas a partitioned RAID volume (e.g. /dev/md0p1) becomes:

set root=(md0,1)

Persistent block device naming

One naming scheme for Persistent block device naming is the use of globally unique UUIDs to detect partitions instead of the "old" /dev/sd*. Advantages are covered up in the above linked article.

Persistent naming via filesystem UUIDs are used by default in GRUB.

Note: The /boot/grub.cfg file needs regeneration with the new UUID in /etc/default/grub every time a relevant filesystem is resized or recreated. Remember this when modifying partitions & filesystems with a Live-CD.

Whether to use UUIDs is controlled by an option in /etc/default/grub:

# GRUB_DISABLE_LINUX_UUID=true

Either way, do not forget to generate the changes:

# grub-mkconfig -o /boot/grub/grub.cfg

Using Labels

It is possible to use labels, human-readable strings attached to filesystems, by using the --label option to search. First of all, label your existing partition:

# tune2fs -L <LABEL> <PARTITION>

Then, add an entry using labels. An example of this:

menuentry "Arch Linux, session texte" {
    search --label --set=root archroot
    linux /boot/vmlinuz-linux root=/dev/disk/by-label/archroot ro
    initrd /boot/initramfs-linux.img
}

Recall previous entry

GRUB can remember the last entry you booted from and use this as the default entry to boot from next time. This is useful if you have multiple kernels (i.e., the current Arch one and the LTS kernel as a fallback option) or operating systems. To do this, edit /etc/default/grub and change the setting of GRUB_DEFAULT:

GRUB_DEFAULT=saved

This ensures that GRUB will default to the saved entry. To enable saving the selected entry, add the following line to /etc/default/grub:

GRUB_SAVEDEFAULT=true
Note: Manually added menu items, eg Windows in /etc/grub.d/40_custom or /boot/grub/custom.cfg , will need savedefault added. Remember to regenerate your configuration file.

Security

If you want to secure GRUB so it is not possible for anyone to change boot parameters or use the command line, you can add a user/password combination to GRUB's configuration files. To do this, run the command grub-mkpasswd-pbkdf2. Enter a password and confirm it. The output will look like this:

Your PBKDF2 is grub.pbkdf2.sha512.10000.C8ABD3E93C4DFC83138B0C7A3D719BC650E6234310DA069E6FDB0DD4156313DA3D0D9BFFC2846C21D5A2DDA515114CF6378F8A064C94198D0618E70D23717E82.509BFA8A4217EAD0B33C87432524C0B6B64B34FBAD22D3E6E6874D9B101996C5F98AB1746FE7C7199147ECF4ABD8661C222EEEDB7D14A843261FFF2C07B1269A
Then, add the following to /etc/grub.d/00_header:
cat << EOF

set superusers="username"
password_pbkdf2 username <password>

EOF

where <password> is the string generated by grub-mkpasswd_pbkdf2.

Regenerate your configuration file. Your GRUB command line, boot parameters and all boot entries are now protected.

This can be relaxed and further customized with more users as described in the "Security" part of the GRUB manual.

Root Encryption

To let GRUB automatically add the kernel parameters for root encryption, add cryptdevice=/dev/yourdevice:label to GRUB_CMDLINE_LINUX in /etc/default/grub.

Example with root mapped to /dev/mapper/root:

GRUB_CMDLINE_LINUX="cryptdevice=/dev/sda2:root"

Also, disable the usage of UUIDs for the rootfs:

GRUB_DISABLE_LINUX_UUID=true

Regenerate the configuration.

Boot non-default entry only once

The command grub-reboot is very helpful to boot another entry than the default only once. GRUB loads the entry passed in the first command line argument, when the system is rebooted the next time. Most importantly GRUB returns to loading the default entry for all future booting. Changing the configuration file or selecting an entry in the GRUB menu is not necessary.

Booting an ISO Directly From GRUB

Edit /etc/grub.d/40_custom or /boot/grub/custom.cfg to add an entry for the target ISO. When finished, update the GRUB menu as with the usual grub-mkconfig -o /boot/grub/grub.cfg (as root).

Arch ISO

Note: The example assumes that the iso is in /archives on hd0,6. Users must adjust the location and hdd/partition in ALL of the lines below to match their systems. However, if booting the ISO from USB on a computer which also has one internal HDD, then it needs to be hd0,Y with sdbY, instead of sdaY.

Example using x86_64

menuentry "Archlinux-2013.01.04-dual.iso" --class iso {
  set isofile="/archives/archlinux-2013.01.04-dual.iso"
  loopback loop (hd0,6)$isofile
  linux (loop)/arch/boot/x86_64/vmlinuz archisolabel=ARCH_201301 img_dev=/dev/sda6 img_loop=$isofile earlymodules=loop
  initrd (loop)/arch/boot/x86_64/archiso.img
}

Example using i686

menuentry "Archlinux-2013.01.04-dual.iso" --class iso {
  set isofile="/archives/archlinux-2013.01.04-dual.iso"
  loopback loop (hd0,6)$isofile
  linux (loop)/arch/boot/i686/vmlinuz archisolabel=ARCH_201301 img_dev=/dev/sda6 img_loop=$isofile earlymodules=loop
  initrd (loop)/arch/boot/i686/archiso.img
}
Tip: For thumbdrives, use Persistent block device names for the "img_dev" kernel parameter. Ex: img_dev=/dev/disk/by-label/CORSAIR

Ubuntu ISO

Note: The example assumes that the iso is in /archives on hd0,6. Users must adjust the location and hdd/partition in the lines below to match their systems.
menuentry "ubuntu-13.04-desktop-amd64.iso" {
    set isofile="/archives/ubuntu-13.04-desktop-amd64.iso"
    loopback loop (hd0,6)$isofile
    linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=$isofile quiet noeject noprompt splash --
    initrd (loop)/casper/initrd.lz
}
menuentry "ubuntu-12.04-desktop-amd64.iso" {
    set isofile="/archives/ubuntu-12.04-desktop-amd64.iso"
    loopback loop (hd0,6)$isofile
    linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile quiet noeject noprompt splash --
    initrd (loop)/casper/initrd.lz
}

Other ISOs

Other working configurations from link Source.

Using the command shell

Since the MBR is too small to store all GRUB modules, only the menu and a few basic commands reside there. The majority of GRUB functionality remains in modules in /boot/grub, which are inserted as needed. In error conditions (e.g. if the partition layout changes) GRUB may fail to boot. When this happens, a command shell may appear.

GRUB offers multiple shells/prompts. If there is a problem reading the menu but the bootloader is able to find the disk, you will likely be dropped to the "normal" shell:

sh:grub>

If there is a more serious problem (e.g. GRUB cannot find required files), you may instead be dropped to the "rescue" shell:

grub rescue>

The rescue shell is a restricted subset of the normal shell, offering much less functionality. If dumped to the rescue shell, first try inserting the "normal" module, then starting the "normal" shell:

grub rescue> set prefix=(hdX,Y)/boot/grub
grub rescue> insmod (hdX,Y)/boot/grub/i386-pc/normal.mod
rescue:grub> normal

Pager support

GRUB supports pager for reading commands that provide long output (like the help command). This works only in normal shell mode and not in rescue mode. To enable pager, in GRUB command shell type:

sh:grub> set pager=1

GUI configuration tools

Following package may be installed from AUR

  • grub-customizerAUR (requires gettext gksu gtkmm hicolor-icon-theme openssl)
    Customize the bootloader (GRUB or BURG)
  • grub2-editorAUR (requires kdelibs)
    A KDE4 control module for configuring the GRUB bootloader
  • kcm-grub2AUR (requires kdelibs python2-qt kdebindings-python)
    This Kcm module manages the most common settings of GRUB.
  • startupmanagerAUR (requires gnome-python imagemagick yelp python2 xorg-xrandr)
    GUI app for changing the settings of GRUB Legacy, GRUB, Usplash and Splashy

parttool for hide/unhide

If you have a Windows 9x paradigm with hidden C:\ disks GRUB can hide/unhide it using parttool. For example, to boot the third C:\ disk of three Windows 9x installations on the CLI enter the CLI and:

parttool hd0,1 hidden+ boot-
parttool hd0,2 hidden+ boot-
parttool hd0,3 hidden- boot+
set root=hd0,3
chainloader +1
boot

Using the rescue console

See #Using the command shell first. If unable to activate the standard shell, one possible solution is to boot using a live CD or some other rescue disk to correct configuration errors and reinstall GRUB. However, such a boot disk is not always available (nor necessary); the rescue console is surprisingly robust.

The available commands in GRUB rescue include insmod, ls, set, and unset. This example uses set and insmod. set modifies variables and insmod inserts new modules to add functionality.

Before starting, the user must know the location of their /boot partition (be it a separate partition, or a subdirectory under their root):

grub rescue> set prefix=(hdX,Y)/boot/grub

where X is the physical drive number and Y is the partition number.

To expand console capabilities, insert the linux module:

grub rescue> insmod (hdX,Y)/boot/grub/linux.mod
Note: With a separate boot partition, omit /boot from the path, (i.e. type set prefix=(hdX,Y)/grub and insmod (hdX,Y)/grub/linux.mod).

This introduces the linux and initrd commands, which should be familiar (see #Configuration).

An example, booting Arch Linux:

set root=(hd0,5)
linux /boot/vmlinuz-linux root=/dev/sda5
initrd /boot/initramfs-linux.img
boot

With a separate boot partition, again change the lines accordingly:

set root=(hd0,5)
linux /vmlinuz-linux root=/dev/sda6
initrd /initramfs-linux.img
boot

After successfully booting the Arch Linux installation, users can correct grub.cfg as needed and then reinstall GRUB.

To reinstall GRUB and fix the problem completely, changing /dev/sda if needed. See #Bootloader installation for details.

Combining the use of UUIDs and basic scripting

If you like the idea of using UUIDs to avoid unreliable BIOS mappings or are struggling with GRUB's syntax, here is an example boot menu item that uses UUIDs and a small script to direct GRUB to the proper disk partitions for your system. All you need to do is replace the UUIDs in the sample with the correct UUIDs for your system. The example applies to a system with a boot and root partition. You will obviously need to modify the GRUB configuration if you have additional partitions:

 menuentry "Arch Linux 64" {
     # Set the UUIDs for your boot and root partition respectively
     set the_boot_uuid=ece0448f-bb08-486d-9864-ac3271bd8d07
     set the_root_uuid=c55da16f-e2af-4603-9e0b-03f5f565ec4a
   
     # (Note: This may be the same as your boot partition)
   
     # Get the boot/root devices and set them in the root and grub_boot variables
     search --fs-uuid --set=root $the_root_uuid
     search --fs-uuid --set=grub_boot $the_boot_uuid
   
     # Check to see if boot and root are equal.
     # If they are, then append /boot to $grub_boot (Since $grub_boot is actually the root partition)
     if [ $the_boot_uuid == $the_root_uuid] ; then
         set grub_boot=$grub_boot/boot
     fi
   
     # $grub_boot now points to the correct location, so the following will properly find the kernel and initrd
     linux ($grub_boot)/vmlinuz-linux root=/dev/disk/by-uuid/$uuid_os_root ro
     initrd ($grub_boot)/initramfs-linux.img
 }

Troubleshooting

Any troubleshooting should be added here.

Intel BIOS not booting GPT

Some Intel BIOS's require at least one bootable MBR partition to be present at boot, causing GPT-partitioned boot setups to be unbootable.

This can be circumvented by using (for instance) fdisk to mark one of the GPT partitions (preferably the 1007KiB partition you've created for GRUB already) bootable in the MBR. This can be achieved, using fdisk, by the following commands: Start fdisk against the disk you're installing, for instance "fdisk /dev/sda", then press "a" and select the partition you wish to mark as bootable (probably #1) by pressing the corresponding number, finally press "w" to write the changes to the MBR.

Note that the bootable-marking must be done in fdisk or similar, not in GParted or others, as they will not set the bootable flag in the MBR.

More information is available here

Enable debug messages

Add:

set pager=1
set debug=all

to grub.cfg.

Correct No Suitable Mode Found Error

If you get this error when booting any menuentry:

error: no suitable mode found
Booting however

Then you need to initialize GRUB graphical terminal (gfxterm) with proper video mode (gfxmode) in GRUB. This video mode is passed by GRUB to the linux kernel via 'gfxpayload'. In case of UEFI systems, if the GRUB video mode is not initialized, no kernel boot messages will be shown in the terminal (atleast until KMS kicks in).

Copy /usr/share/grub/unicode.pf2 to ${GRUB_PREFIX_DIR} (/boot/grub/ in case of BIOS and UEFI systems). If GRUB UEFI was installed with --boot-directory=/boot/efi/EFI set, then the directory is /boot/efi/EFI/grub/:

# cp /usr/share/grub/unicode.pf2 ${GRUB_PREFIX_DIR}

If /usr/share/grub/unicode.pf2 does not exist, install bdf-unifont, create the unifont.pf2 file and then copy it to ${GRUB_PREFIX_DIR}:

# grub-mkfont -o unicode.pf2 /usr/share/fonts/misc/unifont.bdf

Then, in the grub.cfg file, add the following lines to enable GRUB to pass the video mode correctly to the kernel, without of which you will only get a black screen (no output) but booting (actually) proceeds successfully without any system hang.

BIOS systems:

insmod vbe

UEFI systems:

insmod efi_gop
insmod efi_uga

After that add the following code (common to both BIOS and UEFI):

insmod font
if loadfont ${prefix}/fonts/unicode.pf2
then
    insmod gfxterm
    set gfxmode=auto
    set gfxpayload=keep
    terminal_output gfxterm
fi

As you can see for gfxterm (graphical terminal) to function properly, unicode.pf2 font file should exist in ${GRUB_PREFIX_DIR}.

msdos-style error message

grub-setup: warn: This msdos-style partition label has no post-MBR gap; embedding won't be possible!
grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists.
            However, blocklists are UNRELIABLE and its use is discouraged.
grub-setup: error: If you really want blocklists, use --force.

This error may occur when you try installing GRUB in a VMware container. Read more about it here. It happens when the first partition starts just after the MBR (block 63), without the usual space of 1 MiB (2048 blocks) before the first partition. Read #Master Boot Record (MBR) specific instructions

GRUB UEFI drops to shell

If GRUB loads but drops you into the rescue shell with no errors, it may be because of a missing or misplaced grub.cfg. This will happen if GRUB UEFI was installed with --boot-directory and grub.cfg is missing OR if the partition number of the boot partition changed (which is hard-coded into the grubx64.efi file).

GRUB UEFI not loaded

In some cases the EFI may fail to load GRUB correctly. Provided everything is set up correctly, the output of:

efibootmgr -v

might look something like this:

BootCurrent: 0000
Timeout: 3 seconds
BootOrder: 0000,0001,0002
Boot0000* Grub	HD(1,800,32000,23532fbb-1bfa-4e46-851a-b494bfe9478c)File(\efi\grub\grub.efi)
Boot0001* Shell	HD(1,800,32000,23532fbb-1bfa-4e46-851a-b494bfe9478c)File(\EfiShell.efi)
Boot0002* Festplatte	BIOS(2,0,00)P0: SAMSUNG HD204UI

If everything works correctly, the EFI would now automatically load GRUB.

If the screen only goes black for a second and the next boot option is tried afterwards, according to this post, moving GRUB to the partition root can help. The boot option has to be deleted and recreated afterwards. The entry for GRUB should look like this then:

Boot0000* Grub	HD(1,800,32000,23532fbb-1bfa-4e46-851a-b494bfe9478c)File(\grub.efi)

Invalid signature

If trying to boot Windows results in an "invalid signature" error, e.g. after reconfiguring partitions or adding additional hard drives, (re)move GRUB's device configuration and let it reconfigure:

# mv /boot/grub/device.map /boot/grub/device.map-old
# grub-mkconfig -o /boot/grub/grub.cfg

grub-mkconfig should now mention all found boot options, including Windows. If it works, remove /boot/grub/device.map-old.

Boot freezes

If booting gets stuck without any error message after GRUB loading the kernel and the initial ramdisk, try removing the add_efi_memmap kernel parameter.

Restore GRUB Legacy

  • Move GRUB2 files out of the way:
# mv /boot/grub /boot/grub.nonfunctional
  • Copy GRUB Legacy back to /boot:
# cp -af /boot/grub-legacy /boot/grub
  • Replace MBR and next 62 sectors of sda with backed up copy
Warning: This command also restores the partition table, so be careful of overwriting a modified partition table with the old one. It will mess up your system.
# dd if=/path/to/backup/first-sectors of=/dev/sdX bs=512 count=1

A safer way is to restore only the MBR boot code use:

# dd if=/path/to/backup/mbr-boot-code of=/dev/sdX bs=446 count=1

References

  1. Official GRUB Manual - https://www.gnu.org/software/grub/manual/grub.html
  2. Ubuntu wiki page for GRUB - https://help.ubuntu.com/community/Grub2
  3. GRUB wiki page describing steps to compile for UEFI systems - https://help.ubuntu.com/community/UEFIBooting
  4. Wikipedia's page on BIOS Boot partition

External Links

  1. A Linux Bash Shell script to compile and install GRUB for BIOS from BZR Source
  2. A Linux Bash Shell script to compile and install GRUB for UEFI from BZR Source