Difference between revisions of "GRUB"
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− | [[Category:Boot loaders | + | [[Category:Boot loaders]] |
− | + | [[cs:GRUB2]] | |
+ | [[de:GRUB]] | ||
+ | [[es:GRUB2]] | ||
[[fr:GRUB2]] | [[fr:GRUB2]] | ||
+ | [[id:GRUB2]] | ||
+ | [[it:GRUB2]] | ||
+ | [[ru:GRUB2]] | ||
+ | [[tr:GRUB2]] | ||
+ | [[zh-CN:GRUB2]] | ||
+ | [[zh-TW:GRUB2]] | ||
{{Article summary start}} | {{Article summary start}} | ||
{{Article summary text|Covers various aspects of the next generation of the GRand Unified Bootloader (GRUB2).}} | {{Article summary text|Covers various aspects of the next generation of the GRand Unified Bootloader (GRUB2).}} | ||
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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| | + | {{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 link|GNU GRUB | + | {{Article summary wiki|GRUB EFI Examples}} |
+ | {{Article summary link|GNU GRUB - GNU Project|https://www.gnu.org/software/grub/}} | ||
{{Article summary end}} | {{Article summary end}} | ||
− | + | [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]]. | ||
− | + | * From 1.99-6 onwards, GRUB2 supports [[Btrfs]] as root (without a separate {{ic|/boot}} filesystem) compressed with either zlib or LZO. | |
− | + | * For GRUB2 UEFI info, it is recommended to read the [[Unified Extensible Firmware Interface|UEFI]], [[GUID Partition Table|GPT]] and [[UEFI Bootloaders]] pages before reading this page. | |
=== Notes for current GRUB Legacy users === | === Notes for current GRUB Legacy users === | ||
+ | * Upgrade from [[GRUB Legacy]] to GRUB2 is the much same as fresh installing GRUB2 which is covered [[#Installation|below]]. | ||
− | * There are differences in the commands of GRUB and GRUB2. Familiarize yourself with [ | + | * 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"). |
* 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). | * 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). | ||
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==== BIOS systems ==== | ==== BIOS systems ==== | ||
− | ===== [[ | + | ===== [[GUID Partition Table]] (GPT) specific instructions ===== |
− | + | GRUB2 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 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. | |
− | GRUB2 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). | ||
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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. | |
− | + | {{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.}} | ||
− | 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 | + | ===== [[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 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}}). | ||
− | If you | + | 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. |
− | + | 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 ==== | ||
+ | {{Note|It is recommended to read and understand the [[Unified Extensible Firmware Interface|UEFI]], [[GUID Partition Table|GPT]] and [[UEFI Bootloaders]] pages.}} | ||
− | ===== Create and Mount the UEFI | + | ===== 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 {{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: | |
− | Follow [[ | ||
# mkdir -p /boot/efi | # mkdir -p /boot/efi | ||
# mount -t vfat <UEFISYS_PART_DEVICE> /boot/efi | # mount -t vfat <UEFISYS_PART_DEVICE> /boot/efi | ||
− | Create a <UEFI_SYSTEM_PARTITION>/ | + | Create a <UEFI_SYSTEM_PARTITION>{{ic|/EFI}} directory, if it does not exist: |
− | # mkdir -p /boot/efi/ | + | # mkdir -p /boot/efi/EFI |
== Installation == | == Installation == | ||
− | === | + | === BIOS systems === |
− | + | ==== Backup Important Data ==== | |
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− | + | Although a GRUB(2) installation should run smoothly, it is strongly recommended to keep the GRUB Legacy files before installing {{Pkg|grub-bios}}. | |
− | + | # mv /boot/grub /boot/grub-legacy | |
− | + | Backup the MBR which contains the boot code and partition table (Replace {{ic|/dev/sd'''X'''}} 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]]. | |
− | + | ==== Install grub-bios package ==== | |
− | + | The GRUB(2) packages can be installed with pacman (and will replace {{Pkg|grub-legacy}} or {{Pkg|grub}}, if it is installed): | |
+ | |||
+ | # pacman -S grub-bios | ||
− | {{Note| | + | {{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.}} |
− | + | ==== Install grub-bios boot files ==== | |
− | + | There are 3 ways to install GRUB(2) 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}}) | ||
− | + | {{Note|See http://www.gnu.org/software/grub/manual/html_node/BIOS-installation.html for additional documentation.}} | |
− | + | ===== Install to 440-byte MBR boot code region ===== | |
− | + | 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: | |
− | + | # modprobe dm-mod | |
− | + | # grub-install --recheck /dev/sda | |
− | # | + | # grub-mkconfig -o /boot/grub/grub.cfg |
− | + | 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. | |
− | + | {{Note|{{ic|--no-floppy}} has been removed from {{ic|grub-install}} in 2.00~beta2 upstream release, and replaced with {{ic|--allow-floppy}}.}} | |
− | + | {{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 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 {{Keypress|0xEF02}}. With partitioning programs that require setting the GUID directly, it should be {{ic|‘21686148-6449-6e6f-744e656564454649’}} (stored on disk as {{ic|"Hah!IdontNeedEFI"}} 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.}} | |
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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: |
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# modprobe dm-mod | # 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 {{ic|/dev/sda}} is the destination of the installation. | |
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− | where {{ic|/dev/sda}} is the destination of the installation | ||
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− | + | ===== Install to Partition or Partitionless Disk ===== | |
− | {{Note| | + | {{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.}} |
− | To | + | 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): |
− | # | + | # modprobe dm-mod |
− | # | + | # grub-install --target=i386-pc --recheck --debug --force /dev/sdaX |
− | # chattr +i /boot/grub/core.img | + | # 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 {{ic|--force}} option to allow usage of blocklists and should not use {{ic|1=--grub-setup=/bin/true}} (which is similar to simply generating core.img). | + | You need to use the {{ic|--force}} option to allow usage of blocklists and should not use {{ic|1=--grub-setup=/bin/true}} (which is similar to simply generating {{ic|core.img}}). |
− | + | {{ic|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. | + | /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. | + | /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. | However, blocklists are UNRELIABLE and their use is discouraged. | ||
− | Without {{ic|--force}} you may get the below error and grub-setup will not setup its boot code in the partition boot sector | + | Without {{ic|--force}} you may get the below error and {{ic|grub-setup}} will not setup its boot code in the partition boot sector: |
/sbin/grub-setup: error: will not proceed with blocklists | /sbin/grub-setup: error: will not proceed with blocklists | ||
− | With {{ic|--force}} you should get | + | With {{ic|--force}} you should get: |
Installation finished. No error reported. | 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 | + | The reason why {{ic|grub-setup}} does not by default allow this is because in case of partition or a partitionless disk is that {{ic|grub-bios}} relies on embedded blocklists in the partition bootsector to locate the {{ic|/boot/grub/i386-pc/core.img}} file and the prefix dir {{ic|/boot/grub}}. The sector locations of {{ic|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 {{ic|/boot/grub/core.img}} (using chattr command as mentioned above) so that the sector locations of the {{ic|core.img}} file in the disk is not altered. The immutable flag on {{ic|/boot/grub/core.img}} needs to be set only if | + | The workaround for this is to set the immutable flag on {{ic|/boot/grub/i386-pc/core.img}} (using chattr command as mentioned above) so that the sector locations of the {{ic|core.img}} file in the disk is not altered. The immutable flag on {{ic|/boot/grub/i386-pc/core.img}} needs to be set only if {{ic|grub-bios}} is installed to a partition boot sector or a partitionless disk, not in case of installation to MBR or simple generation of {{ic|core.img}} without embedding any bootsector (mentioned above). |
− | + | ===== Generate core.img alone ===== | |
− | To populate the {{ic|/boot/grub}} directory and generate a {{ic|/boot/grub/core.img}} file | + | To populate the {{ic|/boot/grub}} directory and generate a {{ic|/boot/grub/i386-pc/core.img}} file '''without''' embedding any {{ic|grub-bios}} bootsector code in the MBR, post-MBR region, or the partition bootsector, add {{ic|1=--grub-setup=/bin/true}} to {{ic|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 | + | You can then chainload GRUB2's {{ic|core.img}} from GRUB Legacy or syslinux as a Linux kernel or a multiboot kernel. |
− | + | ==== Generate GRUB2 BIOS Config file ==== | |
− | Finally, generate a configuration for | + | Finally, generate a configuration for GRUB2 (this is explained in greater detail in the Configuration section): |
# grub-mkconfig -o /boot/grub/grub.cfg | # grub-mkconfig -o /boot/grub/grub.cfg | ||
− | If | + | {{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 {{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 254: | Line 240: | ||
</nowiki>}} | </nowiki>}} | ||
− | If you forgot to create a GRUB2 {{ic|/boot/grub/grub.cfg}} | + | If you forgot to create a GRUB2 {{ic|/boot/grub/grub.cfg}} config file and simply rebooted into GRUB2 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}} | + | Boot into Arch and re-create the proper GRUB2 {{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 ==== | |
− | + | ===== Boot Microsoft Windows installed in BIOS-MBR mode ===== | |
− | {{Note| | + | {{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.}} |
− | + | {{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="SYSTEM RESERVED"}} and is only about 100 MB in size (much like the boot partition for Arch). See http://en.wikipedia.org/wiki/System_partition_and_boot_partition for more info.}} | |
− | # grub-probe --target=fs_uuid /media/ | + | 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}}: |
+ | |||
+ | For Windows Vista/7/8: | ||
+ | |||
+ | # grub-probe --target=fs_uuid /media/SYSTEM_RESERVED/bootmgr | ||
69B235F6749E84CE | 69B235F6749E84CE | ||
− | + | # grub-probe --target=hints_string /media/SYSTEM_RESERVED/bootmgr | |
+ | --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.}} | ||
− | + | Then, add the below code to {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} and regenerate {{ic|grub.cfg}} with {{ic|grub-mkconfig}} as explained above to boot Windows (XP, Vista, 7 or 8) installed in BIOS-MBR mode: | |
− | + | ||
− | + | For Windows Vista/7/8: | |
− | + | ||
− | + | <pre> | |
− | + | 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 | ||
+ | }</pre> | ||
− | For Windows XP | + | For Windows XP: |
menuentry "Microsoft Windows XP" { | menuentry "Microsoft Windows XP" { | ||
Line 292: | Line 292: | ||
insmod search_fs_uuid | insmod search_fs_uuid | ||
insmod ntldr | insmod ntldr | ||
− | search --fs-uuid -- | + | search --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE |
− | ntldr | + | ntldr /ntldr |
} | } | ||
− | ==== [[UEFI]] | + | {{ic|/etc/grub.d/40_custom}} can be used as a template to create {{ic|/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 recommended to read the [[Unified Extensible Firmware Interface|UEFI]], [[GUID Partition Table|GPT]] and [[UEFI Bootloaders]] pages before reading this part.}} | ||
+ | |||
+ | ==== Hardware-Specific UEFI Examples ==== | ||
− | + | 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 | Depending on that, install the appropriate package | ||
For 64-bit aka x86_64 UEFI firmware: | For 64-bit aka x86_64 UEFI firmware: | ||
− | # pacman -S | + | # pacman -S grub-efi-x86_64 |
For 32-bit aka i386 UEFI firmware: | For 32-bit aka i386 UEFI firmware: | ||
− | # pacman -S | + | # pacman -S grub-efi-i386 |
− | {{Note| | + | {{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.}} |
− | + | ==== Install grub-uefi boot files ==== | |
− | + | ===== 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|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: | |
− | + | # mkdir -p /boot/efi | |
+ | # mount -t vfat /dev/sdXY /boot/efi | ||
− | + | Install GRUB UEFI application to {{ic|/boot/efi/EFI/arch_grub}} and its modules to {{ic|/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 {{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.}} | |
− | + | 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: | |
− | ==== | + | # 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 {{ic|--efi-directory}} option mentions the mountpoint of UEFI SYSTEM PARTITION , {{ic|--bootloader-id}} mentions the name of the directory used to store the {{ic|grubx64.efi}} file and {{ic|--boot-directory}} mentions the directory wherein the actual modules will be installed (and into which {{ic|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 {{ic|--bootloader-id}} option does not change {{ic|<boot-directory>/grub}}, i.e. you cannot install the modules to {{ic|<boot-directory>/<bootloader-id>}}, the path is hard-coded to be {{ic|<boot-directory>/grub}}.}} | |
− | + | In {{ic|<nowiki>--efi-directory=/boot/efi --boot-directory=/boot/efi/EFI --bootloader-id=grub</nowiki>}}: | |
− | |||
− | + | <efi-directory>/<EFI or efi>/<bootloader-id> == <boot-directory>/grub == /boot/efi/EFI/grub | |
− | |||
− | + | In {{ic|<nowiki>--efi-directory=/boot/efi --boot-directory=/boot/efi/EFI --bootloader-id=arch_grub</nowiki>}}: | |
− | + | <efi-directory>/<EFI or efi>/<bootloader-id> == /boot/efi/EFI/arch_grub | |
− | + | <boot-directory>/grub == /boot/efi/EFI/grub | |
− | |||
− | + | In {{ic|<nowiki>--efi-directory=/boot/efi --boot-directory=/boot --bootloader-id=arch_grub</nowiki>}}: | |
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− | + | <efi-directory>/<EFI or efi>/<bootloader-id> == /boot/efi/EFI/arch_grub | |
+ | <boot-directory>/grub == /boot/grub | ||
− | + | In {{ic|<nowiki>--efi-directory=/boot/efi --boot-directory=/boot --bootloader-id=grub</nowiki>}}: | |
− | |||
− | |||
− | + | <efi-directory>/<EFI or efi>/<bootloader-id> == /boot/efi/EFI/grub | |
+ | <boot-directory>/grub == /boot/grub | ||
− | + | The {{ic|<nowiki><efi-directory>/<EFI or efi>/<bootloader-id>/grubx64.efi</nowiki>}} is an exact copy of {{ic|<nowiki><boot-directory>/grub/x86_64-efi/core.efi</nowiki>}}. | |
− | + | {{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.}} | |
− | + | 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. | ||
− | + | 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]]. | |
− | |||
− | |||
− | |||
− | + | ==== Generate GRUB2 UEFI Config file ==== | |
− | + | Finally, generate a configuration for GRUB(2) (this is explained in greater detail in the Configuration section): | |
− | + | # grub-mkconfig -o <boot-directory>/grub/grub.cfg | |
− | + | {{Note|The file path is {{ic|<boot-directory>/grub/grub.cfg}}, NOT {{ic|<boot-directory>/grub/x86_64-efi/grub.cfg}}.}} | |
− | + | If you used {{ic|<nowiki>--boot-directory=/boot</nowiki>}}: | |
− | |||
− | |||
− | + | # grub-mkconfig -o /boot/grub/grub.cfg | |
− | + | If you used {{ic|<nowiki>--boot-directory=/boot/efi/EFI</nowiki>}}: | |
− | |||
− | + | # grub-mkconfig -o /boot/efi/EFI/grub/grub.cfg | |
− | + | 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]]. | |
− | + | ==== Create GRUB2 entry in the Firmware Boot Manager ==== | |
− | If | + | As of grub-efi-x86_64 version 2.00, {{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 GRUB2 Standalone UEFI Application ==== | |
− | It is possible to create a | + | 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. |
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: | ||
− | # | + | # 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 {{ic|grubx64_standalone.efi}} file expects {{ic|grub.cfg}} to be within its $prefix which is {{ic|(memdisk)/boot/grub}}. The memdisk is embedded within the efi app. The {{ic|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 {{ic|grub.cfg}} at {{ic|/home/user/Desktop/grub.cfg}}, then create a temporary {{ic|/home/user/Desktop/boot/grub/}} directory, copy the {{ic|/home/user/Desktop/grub.cfg}} to {{ic|/home/user/Desktop/boot/grub/grub.cfg}}, cd into {{ic|/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 {{ic|/home/user/Desktop/boot/grub/}} and to pass the file path as {{ic|boot/grub/grub.cfg}} (notice the lack of a leading slash - boot/ vs /boot/ ) is because {{ic|dir1/dir2/file}} is included as {{ic|(memdisk)/dir1/dir2/file}} by the {{ic|grub-mkstandalone}} script. | |
− | |||
− | |||
− | |||
− | grub | + | 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 | + | 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]]. |
− | + | ==== Multiboot in UEFI ==== | |
− | + | ===== Chainload Microsoft Windows x86_64 UEFI-GPT ===== | |
− | 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/ | + | 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): |
− | # grub-probe --target=fs_uuid /boot/efi/ | + | # grub-probe --target=fs_uuid /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi |
1ce5-7f28 | 1ce5-7f28 | ||
− | Then, add this code to {{ic|/ | + | # grub-probe --target=hints_string /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi |
+ | --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: | ||
− | menuentry "Microsoft Windows x86_64 UEFI-GPT" { | + | menuentry "Microsoft Windows Vista/7/8 x86_64 UEFI-GPT" { |
insmod part_gpt | insmod part_gpt | ||
insmod fat | insmod fat | ||
insmod search_fs_uuid | insmod search_fs_uuid | ||
insmod chain | insmod chain | ||
− | search --fs-uuid -- | + | search --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1 1ce5-7f28 |
− | chainloader | + | chainloader /efi/Microsoft/Boot/bootmgfw.efi |
} | } | ||
+ | |||
+ | Afterwards remake {{ic|/boot/grub/grub.cfg}} | ||
+ | |||
+ | # grub-mkconfig -o /boot/grub/grub.cfg | ||
== Configuration == | == Configuration == | ||
Line 477: | Line 473: | ||
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| | + | {{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|Here is a quite complete description of how to configure GRUB2: http://members.iinet.net/~herman546/p20/GRUB2%20Configuration%20File%20Commands.html }} | ||
=== Automatically generating using grub-mkconfig (Recommended) === | === Automatically generating using grub-mkconfig (Recommended) === | ||
− | The GRUB2 {{ic|menu. | + | 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: |
+ | |||
# grub-mkconfig -o /boot/grub/grub.cfg | # grub-mkconfig -o /boot/grub/grub.cfg | ||
− | {{ic|/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 | + | |
+ | {{ic|/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 {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} | ||
+ | |||
+ | ==== Additional arguments ==== | ||
+ | |||
+ | To pass custom additional arguments to the Linux image, you can set the {{ic|GRUB_CMDLINE_LINUX}} variable in {{ic|/etc/default/grub}}. | ||
+ | |||
+ | For example, use {{ic|<nowiki>GRUB_CMDLINE_LINUX="resume=/dev/sdaX"</nowiki>}} where {{ic|sda'''X'''}} is your swap partition to enable resume after hibernation. | ||
+ | |||
+ | You can also use {{ic|<nowiki>GRUB_CMDLINE_LINUX="resume=/dev/disk/by-uuid/${swap_uuid}"</nowiki>}}, where {{ic|${swap_uuid} }} is the [[Persistent_block_device_naming|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: | ||
+ | {{ic|<nowiki>GRUB_CMDLINE_LINUX="resume=/dev/sdaX init=/usr/lib/systemd/systemd"</nowiki>}} | ||
+ | |||
+ | See [[Kernel parameters]] for more info. | ||
=== Manually creating grub.cfg === | === Manually creating grub.cfg === | ||
− | A basic | + | {{Warning|Editing this file is strongly ''not'' recommended. The file is generated by the {{ic|grub-mkconfig}} command, and it is best to edit your {{ic|/etc/default/grub}} or one of the scripts in the {{ic|/etc/grub.d}} folder.}} |
+ | |||
+ | A basic GRUB config file uses the following options | ||
* {{ic|(hdX,Y)}} is the partition {{ic|Y}} on disk {{ic|X}}, partition numbers starting at 1, disk numbers starting at 0 | * {{ic|(hdX,Y)}} is the partition {{ic|Y}} on disk {{ic|X}}, partition numbers starting at 1, disk numbers starting at 0 | ||
* {{ic|1=set default=N}} is the default boot entry that is chosen after timeout for user action | * {{ic|1=set default=N}} is the default boot entry that is chosen after timeout for user action | ||
Line 520: | Line 535: | ||
# (0) Arch Linux | # (0) Arch Linux | ||
menuentry "Arch Linux" { | menuentry "Arch Linux" { | ||
− | set root=(hd0,1) | + | set root=(hd0,1) |
− | linux /vmlinuz-linux root=/dev/sda3 ro | + | linux /vmlinuz-linux root=/dev/sda3 ro |
− | initrd /initramfs-linux.img | + | initrd /initramfs-linux.img |
} | } | ||
Line 534: | Line 549: | ||
=== Dual-booting === | === Dual-booting === | ||
− | + | {{Note|If you want GRUB2 to automatically search for other systems, you may wish to install {{Pkg|os-prober}}.}} | |
==== Using grub-mkconfig ==== | ==== Using grub-mkconfig ==== | ||
− | The best way to add other entries is editing the {{ic|/etc/grub.d/40_custom}}. The entries in this file will be automatically added when running | + | The best way to add other entries is editing the {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} . The entries in this file will be automatically added when running {{ic|grub-mkconfig}}. |
After adding the new lines, run: | After adding the new lines, run: | ||
# grub-mkconfig -o /boot/grub/grub.cfg | # grub-mkconfig -o /boot/grub/grub.cfg | ||
Line 563: | Line 578: | ||
===== With Windows ===== | ===== With Windows ===== | ||
− | This assumes that your Windows partition is {{ic|sda3}}. | + | This assumes that your Windows partition is {{ic|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 {{ic|sda3}}. |
# (2) Windows XP | # (2) Windows XP | ||
Line 571: | Line 586: | ||
} | } | ||
− | If the | + | 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 {{ic|drivemap}}. Assuming GRUB is on {{ic|hd0}} and Windows is on {{ic|hd2}}, you need to add the following after {{ic|set root}}: |
drivemap -s hd0 hd2 | drivemap -s hd0 hd2 | ||
Line 584: | Line 599: | ||
title Chainload into GRUB v2 | title Chainload into GRUB v2 | ||
root (hd0,7) | root (hd0,7) | ||
− | kernel /boot/grub/core.img | + | kernel /boot/grub/i386-pc/core.img |
===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, | + | 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. |
====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_GFXMODE=1024x768x32 | GRUB_GFXMODE=1024x768x32 | ||
Line 598: | Line 613: | ||
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 | + | {{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.}} |
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 609: | Line 624: | ||
for eg: {{ic|1="GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=792"}} will give you a {{ic|1024x768}} resolution. | for eg: {{ic|1="GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=792"}} will give you a {{ic|1024x768}} resolution. | ||
− | You can choose one of these resolutions: {{ic|640×480}}, {{ic|800×600}}, {{ic|1024×768}}, {{ic|1280×1024}}, {{ic|1600×1200}} | + | You can choose one of these resolutions: {{ic|640×480}}, {{ic|800×600}}, {{ic|1024×768}}, {{ic|1280×1024}}, {{ic|1600×1200}}, {{ic|1920×1200}} |
+ | |||
+ | ====915resolution hack ==== | ||
+ | |||
+ | 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: | ||
+ | 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 {{ic|/etc/grub.d/00_header}} just before the {{ic|set gfxmode=${GRUB_GFXMODE}}} line insert: | ||
+ | 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: | ||
+ | # grub-mkconfig -o /boot/grub/grub.cfg | ||
+ | # reboot | ||
====Background image and bitmap fonts==== | ====Background image and bitmap fonts==== | ||
− | GRUB2 comes with support for background images and bitmap fonts in pf2 format. The unifont font is included in the | + | 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}}. |
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 [ | + | 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: | ||
− | GRUB_BACKGROUND="/boot/grub/ | + | GRUB_BACKGROUND="/boot/grub/myimage" |
#GRUB_THEME="/path/to/gfxtheme" | #GRUB_THEME="/path/to/gfxtheme" | ||
+ | GRUB_FONT="/path/to/font.pf2" | ||
− | + | {{Note|If you have installed GRUB on a separate partition, {{ic|/boot/grub/myimage}} becomes {{ic|/grub/myimage}}.}} | |
− | |||
− | {{Note|If you have installed | ||
− | To generate the changes and add the information into grub.cfg, run: | + | To generate the changes and add the information into {{ic|grub.cfg}}, run: |
grub-mkconfig -o /boot/grub/grub.cfg | 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 adding the splash image was successful, the user will see {{ic|"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 this phrase is not seen, the image information was probably not incorporated into the {{ic|grub.cfg}} file. |
If the image is not displayed, check: | If the image is not displayed, check: | ||
− | * The path and the filename in /etc/default/grub are correct. | + | * The path and the filename in {{ic|/etc/default/grub}} are correct. |
* The image is of the proper size and format (tga, png, 8-bit jpg). | * 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 image was saved in the RGB mode, and is not indexed. | ||
− | * The console mode is not enabled in /etc/default/grub. | + | * The console mode is not enabled in {{ic|/etc/default/grub}}. |
− | * The command grub-mkconfig must be executed to place the background image information into the /boot/grub/grub.cfg file. | + | * The command {{ic|grub-mkconfig}} must be executed to place the background image information into the {{ic|/boot/grub/grub.cfg}} file. |
+ | |||
+ | ====Theme==== | ||
+ | |||
+ | Here is an example for configuring Starfield theme which was included in GRUB2 package. | ||
+ | |||
+ | Edit {{ic|/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 {{ic|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==== | ====Menu colors==== | ||
− | + | You can set the menu colors in GRUB2. The available colors for GRUB2 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 654: | Line 698: | ||
====Hidden menu==== | ====Hidden menu==== | ||
− | One of the unique features of | + | 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. |
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: | ||
GRUB_HIDDEN_TIMEOUT=5 | GRUB_HIDDEN_TIMEOUT=5 | ||
GRUB_HIDDEN_TIMEOUT_QUIET=false | 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 GRUB2's framebuffer as it can cause problems with the binary driver. | ||
+ | |||
+ | To disable framebuffer, edit {{ic|/etc/default/grub}} and uncomment the following line: | ||
+ | GRUB_TERMINAL_OUTPUT=console | ||
and run: | and run: | ||
Line 673: | Line 727: | ||
and specify your root in the menuentry as: | and specify your root in the menuentry as: | ||
− | set root= | + | set root=lvm/''lvm_group_name''-''lvm_logical_boot_partition_name'' |
Example: | Example: | ||
Line 680: | Line 734: | ||
menuentry "Arch Linux" { | menuentry "Arch Linux" { | ||
insmod lvm | insmod lvm | ||
− | set root= | + | set root=lvm/VolumeGroup-lv_boot |
# you can only set following two lines | # you can only set following two lines | ||
linux /vmlinuz-linux root=/dev/mapper/VolumeGroup-root ro | linux /vmlinuz-linux root=/dev/mapper/VolumeGroup-root ro | ||
Line 686: | Line 740: | ||
} | } | ||
− | ==== | + | ==== 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: | |
− | |||
− | |||
− | which allows you to address the volume natively. | ||
set root=(md0) | set root=(md0) | ||
− | whereas a partitioned | + | whereas a partitioned RAID volume (e.g. {{ic|/dev/md0p1}}) becomes: |
set root=(md0,1) | set root=(md0,1) | ||
==== Persistent block device naming ==== | ==== 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" {{ic|/dev/sd*}}. Advantages are covered up in the above linked article. | |
+ | |||
+ | Persistent naming via filesystem UUIDs are used by default in GRUB2. | ||
+ | |||
+ | {{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.}} | ||
− | UUIDs | + | Whether to use UUIDs is controlled by an option in /etc/default/grub: |
− | + | {{bc|1=# GRUB_DISABLE_LINUX_UUID=true}} | |
− | |||
− | |||
− | |||
Either way, do not forget to generate the changes: | Either way, do not forget to generate the changes: | ||
− | + | {{bc|# grub-mkconfig -o /boot/grub/grub.cfg}} | |
==== Using Labels ==== | ==== Using Labels ==== | ||
It is possible to use labels, human-readable strings attached to filesystems, by using the {{ic|--label}} option to {{ic|search}}. First of all, label your existing partition: | It is possible to use labels, human-readable strings attached to filesystems, by using the {{ic|--label}} option to {{ic|search}}. First of all, label your existing partition: | ||
− | # tune2fs -L | + | # tune2fs -L <LABEL> <PARTITION> |
Then, add an entry using labels. An example of this: | Then, add an entry using labels. An example of this: | ||
menuentry "Arch Linux, session texte" { | menuentry "Arch Linux, session texte" { | ||
− | search --label | + | 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 725: | Line 777: | ||
==== 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_DEFAULT=saved | GRUB_DEFAULT=saved | ||
− | This ensures that | + | This ensures that GRUB will default to the saved entry. To enable saving the selected entry, add the following line to {{ic|/etc/default/grub}}: |
GRUB_SAVEDEFAULT=true | GRUB_SAVEDEFAULT=true | ||
− | Note | + | {{Note|Manually added menu items, eg Windows in {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} , will need {{ic|savedefault}} added. Remember to regenerate your configuration file.}} |
==== 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- | + | 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: |
{{bc|<nowiki> | {{bc|<nowiki> | ||
Line 747: | Line 799: | ||
EOF</nowiki>}} | EOF</nowiki>}} | ||
− | where <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 and boot | + | Regenerate your configuration file. Your GRUB2 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]. | |
− | + | ==== Root Encryption ==== | |
− | menuentry " | + | To let GRUB2 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}}. | |
− | + | ||
− | + | Example with root mapped to {{ic|/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 {{ic|grub-reboot}} is very helpful to boot another entry than the default only once. GRUB2 loads the entry passed in the first command line argument, when the system is rebooted the next time. Most importantly GRUB2 returns to loading the default entry for all future booting. Changing the configuration file or selecting an entry in the GRUB2 menu is not necessary. | ||
+ | |||
+ | === Booting an ISO Directly From GRUB2 === | ||
+ | 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 ==== | ||
+ | {{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}}.}} | ||
+ | |||
+ | '''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_naming|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 {{ic|/archives}} on {{ic|hd0,6}}. Users must adjust the location and hdd/partition in the lines below to match their systems.}} | ||
+ | |||
+ | 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 [http://askubuntu.com/questions/141940/how-to-boot-live-iso-images link Source]. | ||
== Using the command shell == | == Using the command shell == | ||
Line 778: | Line 874: | ||
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: | 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> set prefix=(hdX,Y)/boot/grub | ||
− | grub rescue> insmod (hdX,Y)/boot/grub/normal.mod | + | grub rescue> insmod (hdX,Y)/boot/grub/i386-pc/normal.mod |
rescue:grub> normal | rescue:grub> normal | ||
Line 789: | Line 885: | ||
Following package may be installed from [[AUR]] | Following package may be installed from [[AUR]] | ||
− | * | + | * {{aur|grub-customizer}} (requires gettext gksu gtkmm hicolor-icon-theme openssl) |
+ | *:Customize the bootloader (GRUB2 or BURG) | ||
+ | * {{aur|grub2-editor}} (requires kdelibs) | ||
*:A KDE4 control module for configuring the GRUB2 bootloader | *:A KDE4 control module for configuring the GRUB2 bootloader | ||
− | * | + | * {{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 Grub2. | ||
− | * | + | * {{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, GRUB2, Usplash and Splashy | ||
− | == parttool | + | == parttool for hide/unhide == |
− | If you have a | + | If you have a Windows 9x paradigm with hidden C:\ disks GRUB can hide/unhide it using {{ic|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 hd0,1 hidden+ boot- | ||
parttool hd0,2 hidden+ boot- | parttool hd0,2 hidden+ boot- | ||
Line 810: | Line 908: | ||
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. | 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 | + | The available commands in GRUB rescue include {{ic|insmod}}, {{ic|ls}}, {{ic|set}}, and {{ic|unset}}. This example uses {{ic|set}} and {{ic|insmod}}. {{ic|set}} modifies variables and {{ic|insmod}} inserts new modules to add functionality. |
Before starting, the user must know the location of their {{ic|/boot}} partition (be it a separate partition, or a subdirectory under their root): | Before starting, the user must know the location of their {{ic|/boot}} partition (be it a separate partition, or a subdirectory under their root): | ||
Line 817: | Line 915: | ||
where X is the physical drive number and Y is the partition number. | where X is the physical drive number and Y is the partition number. | ||
− | To expand console capabilities, insert the | + | To expand console capabilities, insert the {{ic|linux}} module: |
grub rescue> insmod (hdX,Y)/boot/grub/linux.mod | grub rescue> insmod (hdX,Y)/boot/grub/linux.mod | ||
{{Note|With a separate boot partition, omit {{ic|/boot}} from the path, (i.e. type {{ic|1=set prefix=(hdX,Y)/grub}} and {{ic|insmod (hdX,Y)/grub/linux.mod}}).}} | {{Note|With a separate boot partition, omit {{ic|/boot}} from the path, (i.e. type {{ic|1=set prefix=(hdX,Y)/grub}} and {{ic|insmod (hdX,Y)/grub/linux.mod}}).}} | ||
− | This introduces the | + | This introduces the {{ic|linux}} and {{ic|initrd}} commands, which should be familiar (see [[#Configuration]]). |
An example, booting Arch Linux: | An example, booting Arch Linux: | ||
Line 836: | Line 934: | ||
boot | boot | ||
− | After successfully booting the Arch Linux installation, users can correct {{ic|grub.cfg}} as needed and then | + | After successfully booting the Arch Linux installation, users can correct {{ic|grub.cfg}} as needed and then reinstall GRUB2. |
− | |||
to reinstall GRUB2 and fix the problem completely, changing {{ic|/dev/sda}} if needed. See [[#Bootloader installation]] for details. | to reinstall GRUB2 and fix the problem completely, changing {{ic|/dev/sda}} if needed. See [[#Bootloader installation]] for details. | ||
− | == Combining the use of | + | == Combining the use of UUIDs and basic scripting == |
− | If you like the idea of using | + | 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" { | 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 | |
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
} | } | ||
Line 877: | Line 970: | ||
=== Enable GRUB2 debug messages === | === Enable GRUB2 debug messages === | ||
− | Add | + | Add: |
set pager=1 | set pager=1 | ||
Line 886: | Line 979: | ||
=== Correct GRUB2 No Suitable Mode Found Error === | === Correct GRUB2 No Suitable Mode Found Error === | ||
− | If you get this error when booting any menuentry | + | If you get this error when booting any menuentry: |
error: no suitable mode found | error: no suitable mode found | ||
Booting however | Booting however | ||
− | Then you need to initialize | + | 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). |
− | Copy {{ic|/usr/share/grub/unicode.pf2}} to ${GRUB2_PREFIX_DIR} ({{ic|/boot/grub/}} in case of BIOS systems | + | 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/}}: |
# cp /usr/share/grub/unicode.pf2 ${GRUB2_PREFIX_DIR} | # cp /usr/share/grub/unicode.pf2 ${GRUB2_PREFIX_DIR} | ||
− | If {{ic|/usr/share/grub/unicode.pf2}} does not exist, install {{Pkg|bdf-unifont}}, create the unifont.pf2 file and then copy it to ${GRUB2_PREFIX_DIR} | + | If {{ic|/usr/share/grub/unicode.pf2}} does not exist, install {{Pkg|bdf-unifont}}, create the {{ic|unifont.pf2}} file and then copy it to {{ic|${GRUB2_PREFIX_DIR<nowiki>}</nowiki>}}: |
# 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 | + | 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. |
− | BIOS systems | + | BIOS systems: |
insmod vbe | insmod vbe | ||
− | UEFI systems | + | UEFI systems: |
insmod efi_gop | insmod efi_gop | ||
insmod efi_uga | insmod efi_uga | ||
− | After that add the following code (common to both BIOS and UEFI) | + | After that add the following code (common to both BIOS and UEFI): |
insmod font | insmod font | ||
− | if loadfont ${prefix}/unicode.pf2 | + | if loadfont ${prefix}/fonts/unicode.pf2 |
then | then | ||
insmod gfxterm | insmod gfxterm | ||
Line 924: | Line 1,017: | ||
fi | fi | ||
− | As you can see for gfxterm (graphical terminal) to | + | As you can see for gfxterm (graphical terminal) to function properly, {{ic|unicode.pf2}} font file should exist in {{ic|${GRUB2_PREFIX_DIR<nowiki>}</nowiki>}}. |
=== msdos-style error message === | === msdos-style error message === | ||
Line 933: | Line 1,026: | ||
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 [ | + | 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 [[#Master Boot Record (MBR) specific instructions]] |
=== UEFI GRUB2 drops to shell === | === UEFI GRUB2 drops to shell === | ||
− | If | + | 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). |
=== UEFI GRUB2 not loaded === | === UEFI GRUB2 not loaded === | ||
− | In some cases the EFI may fail to load | + | In some cases the EFI may fail to load GRUB correctly. Provided everything is set up correctly, the output of: |
efibootmgr -v | efibootmgr -v | ||
might look something like this: | might look something like this: | ||
Line 948: | Line 1,041: | ||
Boot0000* Grub HD(1,800,32000,23532fbb-1bfa-4e46-851a-b494bfe9478c)File(\efi\grub\grub.efi) | 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) | Boot0001* Shell HD(1,800,32000,23532fbb-1bfa-4e46-851a-b494bfe9478c)File(\EfiShell.efi) | ||
− | Boot0002* Festplatte BIOS(2,0,00)P0: SAMSUNG HD204UI | + | Boot0002* Festplatte BIOS(2,0,00)P0: SAMSUNG HD204UI |
− | If everything works correctly, the EFI would now automatically load | + | 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 [https://bbs.archlinux.org/viewtopic.php?pid=981560#p981560 this post], moving | + | |
+ | If the screen only goes black for a second and the next boot option is tried afterwards, according to [https://bbs.archlinux.org/viewtopic.php?pid=981560#p981560 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) | Boot0000* Grub HD(1,800,32000,23532fbb-1bfa-4e46-851a-b494bfe9478c)File(\grub.efi) | ||
=== Invalid signature === | === Invalid signature === | ||
− | If trying to boot | + | 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 | # mv /boot/grub/device.map /boot/grub/device.map-old | ||
# grub-mkconfig -o /boot/grub/grub.cfg | # grub-mkconfig -o /boot/grub/grub.cfg | ||
− | + | {{ic|grub-mkconfig}} should now mention all found boot options, including Windows. If it works, remove {{ic|/boot/grub/device.map-old}}. | |
+ | |||
+ | === 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. | ||
+ | |||
+ | === Restore GRUB Legacy === | ||
+ | |||
+ | * Move GRUB2 files out of the way: | ||
+ | |||
+ | # mv /boot/grub /boot/grub.nonfunctional | ||
+ | |||
+ | * Copy GRUB Legacy back to {{ic|/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 == | == References == | ||
− | # Official GRUB2 Manual - | + | # Official GRUB2 Manual - https://www.gnu.org/software/grub/manual/grub.html |
− | # Ubuntu wiki page for | + | # Ubuntu wiki page for GRUB2 - https://help.ubuntu.com/community/Grub2 |
# GRUB2 wiki page describing steps to compile for UEFI systems - https://help.ubuntu.com/community/UEFIBooting | # GRUB2 wiki page describing steps to compile for UEFI systems - https://help.ubuntu.com/community/UEFIBooting | ||
− | # Wikipedia's page on [ | + | # 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/ | + | # [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/ | + | # [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] |
Revision as of 16:03, 10 April 2013
zh-CN:GRUB2 zh-TW:GRUB2 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 GRUB2 is the next generation of the GRand Unified Bootloader (GRUB). GRUB2 is derived from 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 [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
- 1 Preface
- 2 Installation
- 2.1 BIOS systems
- 2.2 UEFI systems
- 3 Configuration
- 4 Using the command shell
- 5 GUI configuration tools
- 6 parttool for hide/unhide
- 7 Using the rescue console
- 8 Combining the use of UUIDs and basic scripting
- 9 Troubleshooting
- 10 References
- 11 External Links
Preface
Here is some information that needs to be clarified:
- 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.
- From 1.99-6 onwards, GRUB2 supports Btrfs as root (without a separate
/boot
filesystem) compressed with either zlib or LZO.
- For GRUB2 UEFI info, it is recommended to read the UEFI, GPT and UEFI Bootloaders pages before reading this page.
Notes for current GRUB Legacy users
- Upgrade from GRUB Legacy to GRUB2 is the much same as fresh installing GRUB2 which is covered below.
- There are differences in the commands of GRUB and GRUB2. Familiarize yourself with GRUB2 commands before proceeding (e.g. "find" has been replaced with "search").
- 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).
- 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,
/dev/sda1
would be referred to as(hd0,msdos1)
(for MBR) or(hd0,gpt1)
(for GPT) using GRUB2.
Preliminary Requirements for GRUB2
BIOS systems
GUID Partition Table (GPT) specific instructions
GRUB2 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 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.
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.
grub-install
or grub-setup
is run.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 GRUB2'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 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.
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
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 UEFISYS partition in some other mountpoint, replace /boot/efi
in the below instructions with that mountpoint:
# mkdir -p /boot/efi # mount -t vfat <UEFISYS_PART_DEVICE> /boot/efi
Create a <UEFI_SYSTEM_PARTITION>/EFI
directory, if it does not exist:
# mkdir -p /boot/efi/EFI
Installation
BIOS systems
Backup Important Data
Although a GRUB(2) installation should run smoothly, it is strongly recommended to keep the GRUB Legacy files before installing grub-bios.
# 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.
Install grub-bios package
The GRUB(2) packages can be installed with pacman (and will replace grub-legacy or grub, if it is installed):
# pacman -S grub-bios
/boot/grub/i386-pc/core.img
file and the GRUB(2) modules in /boot/grub/i386-pc
. You need to update them manually using grub-install
as explained below.Install grub-bios boot files
There are 3 ways to install GRUB(2) 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
/boot/grub/i386-pc/core.img
)
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 GRUB2 on multiple physical disks.
--no-floppy
has been removed from grub-install
in 2.00~beta2 upstream release, and replaced with --allow-floppy
./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 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 Template:Keypress. With partitioning programs that require setting the GUID directly, it should be ‘21686148-6449-6e6f-744e656564454649’
(stored on disk as "Hah!IdontNeedEFI"
if interpreted as ASCII).
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 Partition or Partitionless Disk
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.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 GRUB2's core.img
from GRUB Legacy or syslinux as a Linux kernel or a multiboot kernel.
Generate GRUB2 BIOS Config file
Finally, generate a configuration for GRUB2 (this is explained in greater detail in the Configuration section):
# grub-mkconfig -o /boot/grub/grub.cfg
/boot/grub/grub.cfg
, NOT /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-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 GRUB2 /boot/grub/grub.cfg
config file and simply rebooted into GRUB2 Command Shell, type:
sh:grub> insmod legacycfg sh:grub> legacy_configfile ${prefix}/menu.lst
Boot into Arch and re-create the proper GRUB2 /boot/grub/grub.cfg
config file.
Multiboot in BIOS
Boot Microsoft Windows installed in BIOS-MBR mode
bootmgr
directly and chainload of partition boot sector is no longer required to boot Windows in a BIOS-MBR setup.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 http://en.wikipedia.org/wiki/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
grub-probe
should be run as root.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.
UEFI systems
Hardware-Specific UEFI Examples
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
GRUB(2) UEFI bootloader is available in Arch Linux only from version 1.99~rc1. To install, first 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:
# pacman -S grub-efi-x86_64
For 32-bit aka i386 UEFI firmware:
# pacman -S grub-efi-i386
core.efi
file and the GRUB(2) modules in the UEFI System Partition. You need to do this manually using grub-install
as explained below.Install grub-uefi boot files
Install to UEFI System Partition
grub-efi-x86_64
(for grub-efi-i386
replace x86_64
with i386
in the below commands).The UEFI system partition will need to be mounted at /boot/efi/
for the GRUB(2) 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
--target
or --directory
option, grub-install cannot determine for which firmware grub(2) 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(2) 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(2) 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>
--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
.
grub-install
option --efi-directory
replaces --root-directory
and the latter is deprecated.--efi-directory
and --bootloader-id
are specific to GRUB(2) 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(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.
You may now be able to UEFI boot your system by creating a grub.cfg
file by following #Generate GRUB2 UEFI Config file and #Create GRUB2 entry in the Firmware Boot Manager.
Generate GRUB2 UEFI Config file
Finally, generate a configuration for GRUB(2) (this is explained in greater detail in the Configuration section):
# grub-mkconfig -o <boot-directory>/grub/grub.cfg
<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 GRUB2 complains about "no suitable mode found" while booting, try #Correct GRUB2 No Suitable Mode Found Error.
Create GRUB2 entry in the Firmware Boot Manager
As of grub-efi-x86_64 version 2.00, 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 GRUB2 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 GRUB2 uefi modules and other related files. This is done using the grub-mkstandalone
command which is included in grub-common >= 1:1.99-6 package.
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 GRUB2 entry in the Firmware Boot Manager.
Multiboot in UEFI
Chainload Microsoft Windows x86_64 UEFI-GPT
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
grub-probe
should be run as root.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
.
--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 the BIOS version of GRUB2.Automatically generating using grub-mkconfig (Recommended)
The GRUB2 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
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 partitionY
on diskX
, 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 timeM
to wait in seconds for a user selection before default is booted -
menuentry "title" {entry options}
is a boot entry titledtitle
-
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 GRUB2 - 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
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 GRUB2 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 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.
Setting the framebuffer resolution
GRUB2 can set the framebuffer for both GRUB2 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.
gfxmode="1024x768x32"
by vbemode="0x105"
. Remember to replace the specified resolution with one suitable for your screen.# hwinfo --framebuffer
(hwinfo is available in [community]), while at GRUB2 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 GRUB2 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 GRUB2 configuration file and reboot to test changes:
# grub-mkconfig -o /boot/grub/grub.cfg # reboot
Background image and bitmap fonts
GRUB2 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"
/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 GRUB2 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 GRUB2. The available colors for GRUB2 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
One of the unique features of GRUB2 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 GRUB2'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
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
GRUB2 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 GRUB2.
/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
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 /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
/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 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 grub-mkpasswd-pbkdf2
. Enter a password and confirm it. The output will look like this:
Your PBKDF2 is grub.pbkdf2.sha512.10000.C8ABD3E93C4DFC83138B0C7A3D719BC650E6234310DA069E6FDB0DD4156313DA3D0D9BFFC2846C21D5A2DDA515114CF6378F8A064C94198D0618E70D23717E82.509BFA8A4217EAD0B33C87432524C0B6B64B34FBAD22D3E6E6874D9B101996C5F98AB1746FE7C7199147ECF4ABD8661C222EEEDB7D14A843261FFF2C07B1269AThen, 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 GRUB2 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 GRUB2 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. GRUB2 loads the entry passed in the first command line argument, when the system is rebooted the next time. Most importantly GRUB2 returns to loading the default entry for all future booting. Changing the configuration file or selecting an entry in the GRUB2 menu is not necessary.
Booting an ISO Directly From GRUB2
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
/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 }
Ubuntu ISO
/archives
on hd0,6
. Users must adjust the location and hdd/partition in the lines below to match their systems.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 GRUB2 modules, only the menu and a few basic commands reside there. The majority of GRUB2 functionality remains in modules in /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.
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:
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
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:
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 (GRUB2 or BURG)
- grub2-editorAUR (requires kdelibs)
- A KDE4 control module for configuring the GRUB2 bootloader
- kcm-grub2AUR (requires kdelibs python2-qt kdebindings-python)
- This Kcm module manages the most common settings of Grub2.
- startupmanagerAUR (requires gnome-python imagemagick yelp python2 xorg-xrandr)
- GUI app for changing the settings of GRUB, GRUB2, 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
/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 GRUB2.
to reinstall GRUB2 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.
Enable GRUB2 debug messages
Add:
set pager=1 set debug=all
to grub.cfg
.
Correct GRUB2 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 GRUB2 graphical terminal (gfxterm
) with proper video mode (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).
Copy /usr/share/grub/unicode.pf2
to ${GRUB2_PREFIX_DIR} (/boot/grub/
in case of BIOS and UEFI systems). If GRUB2 UEFI was installed with --boot-directory=/boot/efi/EFI
set, then the directory is /boot/efi/EFI/grub/
:
# cp /usr/share/grub/unicode.pf2 ${GRUB2_PREFIX_DIR}
If /usr/share/grub/unicode.pf2
does not exist, install bdf-unifont, create the unifont.pf2
file and then copy it to ${GRUB2_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 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.
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 ${GRUB2_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 GRUB2 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
UEFI GRUB2 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 GRUB2 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).
UEFI GRUB2 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 grub2 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
# 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
- Official GRUB2 Manual - https://www.gnu.org/software/grub/manual/grub.html
- Ubuntu wiki page for GRUB2 - https://help.ubuntu.com/community/Grub2
- GRUB2 wiki page describing steps to compile for UEFI systems - https://help.ubuntu.com/community/UEFIBooting
- Wikipedia's page on BIOS Boot partition