Difference between revisions of "GRUB"

[[Category:Boot loaders (English)]]

{{i18n|GRUB2}}

{{Article summary wiki|Burg}} - Burg is a brand-new boot loader based on GRUB2. It uses a new object format which allows it to be built in a wider range of OS, including Linux/Windows/OSX/Solaris/FreeBSD, etc. It also has a highly configurable menu system which works in both text and graphic mode.  

{{Article summary link|GNU GRUB -- GNU Project|http://www.gnu.org/software/grub/}}

 

[http://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. GRUB 2 has been rewritten from scratch to clean up everything and provide modularity and portability [http://www.gnu.org/software/grub/grub-faq.en.html#q1].

Although, [[GRUB]] (i.e. version 0.9x) is the de facto standard bootloader of Linux, it is considered 'legacy' by upstream. It is being replaced by GRUB2 in many distributions. Upstream recommends GRUB2 >=1.99~rc2 over grub-legacy, even for current grub-legacy users.

{{Note|grub2 from 1.99~rc2 and later supports btrfs as root (without a separate /boot filesystem).}}

* There are differences in the commands of GRUB and GRUB2. Familiarize yourself with [http://www.gnu.org/software/grub/manual/grub.html#Commands GRUB2 commands] before proceeding (e.g. "find" has been replaced with "search").

===== [[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 2 MiB partition using cgdisk or GNU Parted with no filesystem. The location of the partition in the partition table does not matter but it should be within the first 2 TiB region of the disk. It is advisable to put it somewhere in the beginning of the disk before the /boot partition. Set the partition type to "EF02" in cgdisk or {{ic|set <BOOT_PART_NUM> bios_grub on}} in GNU Parted.

{{Note|This partition should be created before grub_bios-install or grub-setup is run or before the '''Install Bootloader''' step of the Archlinux installer (if GRUB2 BIOS is selected as bootloader).}}

===== [[MBR]] aka msdos partitioning 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 32 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 ( https://bugs.archlinux.org/task/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).

 

If you do not dual-boot with MS Windows (any version) in BIOS systems, it is advisable to switch to GPT partitioning - [[GUID_Partition_Table#Convert_from_MBR_to_GPT_without_data_loss]]

 

===== Create and Mount the UEFI SYSTEM PARTITION =====

 

Follow [[Unified_Extensible_Firmware_Interface#Create_an_UEFI_SYSTEM_PARTITION_in_Linux]] for instructions on creating a UEFI SYSTEM PARTITION. Then mount the UEFI SYSTEM PARTITION at {{ic|/boot/efi}}. It should be FAT32 formatted and should be >=200 MiB in size. If you have mounted the UEFISYS partition in some other mountpoint, replace {{ic|/boot/efi}} in the below instructions with that mountpoint:

Create a <UEFI_SYSTEM_PARTITION>/efi directory if it does not exist:

  # mkdir -p /boot/efi/efi

=== During Arch Linux installation ===

=== From a running Arch Linux ===

===== Backup Important Data =====

In general, a grub installation should run smoothly. Sometimes it could mess up your system. You're strongly advised to make a backup before installing grub2-bios.

  # cp -a /boot/grub /path/to/backup/

* backup the MBR and GRUB-Legacy stage 1.5

# dd if=/dev/sdX of=/path/to/backup/first-sectors bs=512 count=63

Replace /dev/sdaX with you disk path (mostly /dev/sda).

{{Note|This command backs up the partition table too. Be careful while restoring if you've changed your partition setup in the meantime}}

To backup only the MBR boot code use:

# dd if=/dev/sdX of=/path/to/backup/mbr-boot-code bs=440 count=1

You could now lightly remove {{ic|/boot/grub}} with:

# rm -rf /boot/grub

and follow the instructions below. You know that if things get nasty, you could reboot your system thanks to an installation media and:

* move old grub-legacy or grub2 files out of the way

# mv /boot/grub /boot/grub.nonfunctional

* copy grub back to /boot

# cp -a /path/to/backup/grub /boot/

  # dd if=/path/to/backup/first-sectors of=/dev/sdX bs=512 count=63

{{Note|This command also restores the partition table. Be careful.}}

# dd if=/path/to/backup/mbr-boot-code of=/dev/sdX bs=440 count=1

The GRUB2 package can be installed with pacman (and will replace {{Pkg|grub}}, if it is installed). Simply installing the package won't update the {{ic|/boot/grub/core.img}} file and the grub2 modules in {{ic|/boot/grub}}. You need to update them manually using grub_bios-install as explained below.

 

{{Note|Installing grub2-common (a dependency of grub2-bios) 1.99~rc1 or later, may take forever in some systems since the post_install script runs grub-mkconfig and this script does not provide the option {{ic|--no-floppy}}. For more details search this option in the article.}}

 

Also load the device-mapper kernel module without which grub-probe does not reliably detect disks and partitions:

 

*[[#Generate_core.img_alone]] (safest method, but requires another BIOS bootloader like [[grub-legacy]] or [[syslinux]] to be installed to chainload {{ic|/boot/grub/core.img}} ).

 

 

To setup grub2-bios in the 440-byte Master Boot Record boot code region, populate the {{ic|/boot/grub}} directory, generate the {{ic|/boot/grub/core.img}} file, and embed it in the 32 KiB (minimum size - varies depending on partition alignment) post-MBR gap (MBR disks) or in BIOS Boot Partition (GPT disks), run:

# grub_bios-install --boot-directory=/boot --no-floppy --recheck --debug /dev/sda

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.  

The {{ic|--no-floppy}} tells grub2-bios utilities not to search for any floppy devices which reduces the overall execution time of grub_bios-install on many systems (it will also prevent the issue below from occurring). Otherwise you get an error like this:

 

grub-probe: error: Cannot get the real path of '/dev/fd0'

 

 

{{Note|grub2-bios (any version - including upstream bzr repo) does not encourage installation to a partition boot sector or a partitionless disk like grub-legacy or syslinux does. Neither do the Arch devs.}}

 

To setup grub2-bios to a partition boot sector, to a partitionless disk (also called superfloppy) or to a floppy disk, run (using for example /dev/sda1 as the /boot partition)

  # chattr -i /boot/grub/core.img

  # grub_bios-install --boot-directory=/boot --no-floppy --recheck --force --debug /dev/sda1

  # chattr +i /boot/grub/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).

grub_bios-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.

Without {{ic|--force}} you may get the below error and grub-setup will not setup its boot code in the partition boot sector.

With {{ic|--force}} you should get

The reason why grub-setup does not by default allow this is because in case of partition or a partitionless disk is that grub2-bios relies on embedded blocklists in the partition bootsector to locate the {{ic|/boot/grub/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 grub2-bios is installed to a partition boot sector or a partitionless disk, not in case of installtion 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 WITHOUT embedding any grub2-bios bootsector code in the MBR, post-MBR region, or the partition bootsector, add {{ic|1=--grub-setup=/bin/true}} to grub_bios-install:

  # grub_bios-install --grub-setup=/bin/true --boot-directory=/boot --no-floppy --recheck --debug /dev/sda

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):

If grub2 complains about "no suitable mode found" while booting, go to [[#Correct_GRUB2_No_Suitable_Mode_Found_Error]] .

If you forgot to create a GRUB2 {{ic|/boot/grub/grub.cfg}} configfile and simply rebooted into GRUB2 Command Shell, type:

Boot into Arch and re-create the proper GRUB2 {{ic|/boot/grub/grub.cfg}} configfile.

===== Multiboot in BIOS =====

====== Boot Microsoft Windows installed in BIOS-MBR mode ======

{{Note|GRUB2 supports booting {{ic|bootmgr}} directly and chainload of partition boot sector is no longer required to boot Windows in a BIOS-MBR setup.}}

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

  # grub-probe --target=fs_uuid /media/Windows/bootmgr

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

menuentry "Microsoft Windows 7 BIOS-MBR" {

    insmod part_msdos

    insmod ntfs

    insmod search_fs_uuid

    insmod ntldr     

    search --fs-uuid --no-floppy --set=root 69B235F6749E84CE

    ntldr (${root})/bootmgr

}

For Windows XP

     search --fs-uuid --no-floppy --set=root 69B235F6749E84CE

     ntldr (${root})/ntldr

{{Note|Unless specified as EFI 1.x , EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware. Also unless stated explicitely, 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.}}

GRUB2 UEFI bootloader is available in Arch Linux only from version 1.99~rc1. To install, first [https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface#Detecting_UEFI_Firmware_Arch Detect which UEFI firmware arch] you have (either x86_64 or i386).

  # pacman -S grub2-efi-x86_64

  # pacman -S grub2-efi-i386

{{Note|Installing grub2-common (a dependency of grub2-bios) 1.99~rc1 or later, may take forever in some systems since the post_install script runs grub-mkconfig and this script does not provide the option {{ic|--no-floppy}}. For more details search this option in the article.}}

{{Note|Simply installing the package won't update the grub.efi file and the grub2 modules in the UEFI System Partition. You need to update the grub.efi file and the grub2 modules in the UEFI System Partition manually using grub_efi_${UEFI_ARCH}-install as explained below.}}

# modprobe dm-mod

===== Install grub2-uefi boot files =====

====== Install to UEFI SYSTEM PARTITION ======

{{Note|The below commands assume you are using {{ic|grub2-efi-x86_64}} (for {{ic|grub2-efi-i386}} replace {{ic|x86_64}} with {{ic|i386}} in the below commands).}}

# grub_efi_x86_64-install --root-directory=/boot/efi --boot-directory=/boot/efi/efi --bootloader-id=grub --no-floppy --recheck --debug

The {{ic|grub_efi_x86_64-install}} automatically generates a {{ic|grub.efi}} while setting up the {{ic|/boot/efi/efi/grub/}} directory.

If you notice carefully, there is no <device_path> option (Eg: {{ic|/dev/sda}}) at the end of the {{ic|grub_efi_x86_64-install}} command unlike the case of setting up grub2 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 copying /boot/efi/efi/grub/grubx64.efi to /boot/efi/efi/boot/bootx64.efi.

===== Create GRUB2 entry in the Firmware Boot Manager =====

====== Non-Mac UEFI systems ======

{{Note|The below steps will not work if the system has been booted in BIOS mode and will not work if the UEFI processor architecture does not match the kernel one, i.e. x86_64 UEFI + ix86 32-bit Kernel and vice-versa config will not work. This is true only for efivars kernel module and efibootmgr step. The other steps (ie. upto setting up <UEFISYS>/efi/grub/grub.{efi,cfg} ) can be done even in BIOS/Legacy boot mode.}}

{{Warning|Using {{ic|efibootmgr}} in Apple Macs will brick the firmware and may need reflash of the motherboard ROM. There have been bug reports regarding this in Ubuntu/Launchpad bug tracker. Use bless command alone in case of Macs (see chapter regarding Apple systems}}

grub_efi_${UEFI_ARCH}-install will ensure {{ic|/boot/efi/efi/grub/grub.efi}} is launched by default if it detects {{ic|efibootmgr}} and if it is able to access UEFI Runtime Services. {{ic|efibootmgr}} command will work only if you have booted the system in UEFI mode itself, since it '''requires access to UEFI Runtime Variables''' which are '''available only in UEFI boot mode''' (with "noefi" kernel parameter NOT being used).  Initially the user is required to manually launch {{ic|/boot/efi/efi/grub/grub.efi}} from the firmware itself (using maybe the UEFI Shell) if grub2-efi was installed in BIOS mode. Then {{ic|efibootmgr}} should be run to make grub2 as the default entry in the UEFI Boot Manager

First boot into UEFI mode manually either using the firmware boot menu, UEFI shell, or using any UEFI capable bootable iso (Archboot or Ubuntu non-Mac iso). Use grub probe to determine the device path of your EFI System Partition:

# grub-probe --target=device /boot/efi/efi/grub/grub.efi

It should give something like {{ic|/dev/sda1}} (used as example in the remaining steps). Load 'efivars' kernel module:

Verify whether there are files in ''/sys/firmware/efi/vars/'' directory. This directory and its contents are created by "efivars" kernel module and it will exist only if you have booted in UEFI mode without the "noefi" kernel parameter.

   

# ls -1 /sys/firmware/efi/vars/

Sample output (x86_64-UEFI 2.3.1 in x86_64 Kernel:

# ls -1 /sys/firmware/efi/vars/

Boot0000-8be4df61-93ca-11d2-aa0d-00e098032b8c/

BootCurrent-8be4df61-93ca-11d2-aa0d-00e098032b8c/

BootOptionSupport-8be4df61-93ca-11d2-aa0d-00e098032b8c/

BootOrder-8be4df61-93ca-11d2-aa0d-00e098032b8c/

If ''/sys/firmware/efi/vars/'' directory is empty or does not exist, then {{ic|efibootmgr}} command will not work. If you are unable to make the ISO/CD/DVD/USB boot in UEFI mode try https://gitorious.org/tianocore_uefi_duet_builds/pages/Linux_Windows_BIOS_UEFI_boot_USB.

If ''/sys/firmware/efi/vars/'' directory (along with the exists then run {{ic|efibootmgr}} and reboot:

# efibootmgr --create --gpt --disk /dev/sda --part 1 --write-signature --label "GRUB2" --loader "\\EFI\\grub\\grub.efi"

In the above command, {{ic|/boot/efi/efi/grub/grub.efi}} can be split up as {{ic|/boot/efi}} and {{ic|/efi/grub/grub.efi}}, which translates to {{ic|(/dev/sda)}} -> partition 1 -> {{ic|\\EFI\\grub\\grub.efi}}.

FAT32 filesystem is case-insensitive since it does not use UTF-8 encoding by default. In that case the firmware uses capital 'EFI' instead of small 'efi', therefore using {{ic|\\EFI\\grub\\grub.efi}} or {{ic|\\efi\\grub\\grub.efi}} does not matter (this will change if the filesystem encoding is UTF-8). UEFI uses backward slash as path separatoir (similar to Windows paths). In the above command "double" backward slashes are used instead of single ones, since a backward slash is used as a escape character by sh shells, the first backward slash escapes the second one so that the path {{ic|\EFI\grub\grub.efi}} is passed to {{ic|efibootmgr}}.

The 'label' is the name of the menu entry shown in the UEFI boot menu. This name is user's choice and does not affect the booting of the system. More info can be obtained from [http://linux.dell.com/cgi-bin/gitweb/gitweb.cgi?p=efibootmgr.git;a=blob_plain;f=README;hb=HEAD efibootmgr GIT README]

If you have problems running GRUB2 in UEFI mode you can try the following (worked on an ASUS Z68 mainboard):

# cp /boot/efi/efi/grub/grubx64.efi /boot/efi/shellx64.efi

# cp /boot/efi/efi/grub/grubx64.efi /boot/efi/efi/shellx64.efi

# cp /boot/efi/efi/grub/grubx64.efi /boot/efi/efi/shell/shellx64.efi

After this launch the UEFI Shell from the UEFI setup/menu (in ASUS UEFI BIOS, switch to advanced mode, press Exit in the top right corner and choose "Launch EFI shell from filesystem device"). The grub2 menu will show up and you can boot into your system. Afterwards you can use efibootmgr to setup a menu entry (see above).

Use bless command from within Mac OS X to set {{ic|grub.efi}} as the default boot option. You can also boot from the Mac OS X install disc and launch a Terminal there if you only have Linux installed. In the Terminal, create a directory and mount the EFI System Partition:

# mount -t msdos /dev/disk0s1 /Volumes/efi

Then run bless on {{ic|grub.efi}} and on the EFI partition to set them as the default boot options.

# bless --folder=/Volumes/efi --file=/Volumes/efi/efi/grub/grub.efi --setBoot

More info at https://help.ubuntu.com/community/UEFIBooting#Apple_Mac_EFI_systems_.28both_EFI_architecture.29.

Finally, generate a configuration for grub2 (this is explained in greater detail in the Configuration section):

If grub2-uefi complains about "no suitable mode found" while booting, go to [[#Correct_GRUB2_No_Suitable_Mode_Found_Error]].

===== Create GRUB2 Standalone UEFI Application =====

It is possible to create a grub_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.  

  # grub_efi_x86_64-install --root-directory=/boot/efi --boot-directory=/boot/efi/efi --bootloader-id=grub --no-floppy --recheck --debug \

  --modules="normal help ext2 video efi_gop gfxterm gzio"

However, you might want to embed certain configuration as well, for which you might want to use a script like this:

{{hc|grub_image_helper|

#!/bin/bash

ARCH=${1:-x86_64-efi}

cat << EOF > "grub.cfg"

search --no-floppy --fs-uuid --set=grub_root 5EF2-55E6

set prefix=(\$grub_root)/efi/grub

grub-mkimage --format=$ARCH --compression=xz --output=/boot/efi/efi/grub/grub_standalone.efi --config grub.cfg '--prefix=(,gpt1)/efi/grub' fat part_gpt search</nowiki>}}

You would need to create an entry with {{ic|efibootmgr}} for grub_standalone.efi, just use grub.efi instead to replace the original, or you can use the UEFI shell to try it out first. See [[#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/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

Then, add this code to {{ic|/boot/efi/efi/grub/grub.cfg}} to chainload Windows x86_64 (Vista SP1+, 7 or 8) installed in UEFI-GPT mode:

  menuentry "Microsoft Windows x86_64 UEFI-GPT" {

     search --fs-uuid --no-floppy --set=root 1ce5-7f28

     chainloader (${root})/efi/Microsoft/Boot/bootmgfw.efi

{{Note|If using UEFI {{ic|grub.cfg}} must be placed alongside {{ic|grub.efl}} on the UEFI system partition. The easiest way is to copy the configuration file created below from {{ic|/boot/grub/grub.cfg}} to {{ic|/boot/efi/EFI/grub}} where {{ic|/boot/efi}} is the mounted UEFI partition. }}

The GRUB2 {{ic|menu.1st}} equivalent configuration files are {{ic|/etc/default/grub}} and {{ic|/etc/grub.d/*}}. 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:

{{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 by editing {{ic|/etc/grub.d/40_custom}}

A basic grub file uses the following options

set root=(hd0,1)

linux /vmlinuz-linux root=/dev/sda3 ro

initrd /initramfs-linux.img

''NOTE: If you want GRUB2 to automatically search for other systems, for example as in Ubuntu. Then you may need to download {{AUR|os-prober}} from the [[AUR]].''

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 '''grub-mkconfig'''.

This assumes that your Windows partition is {{ic|sda3}}.

If the windows bootloader is on an entirely different harddrive than grub, it may be necessary to trick Windows into believing that it is in fact the first harddrive. This was possible in the old grub with {{ic|map}} and is now done with {{ic|drivemap}}. Assume grub is on {{ic|hd0}} and windows on {{ic|hd2}}, you need to add the following after {{ic|set root}}:

  kernel      /boot/grub/core.img

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.

Grub2 can set the framebuffer for both grub2 itself and the kernel. The old ''vga='' way is deprecated. The preferred method is editing {{ic|/etc/default/grub}} as the following sample:

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

{{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.}}

You can choose one of these resolutions: {{ic|640×480}}, {{ic|800×600}}, {{ic|1024×768}}, {{ic|1280×1024}}, {{ic|1600×1200}}

GRUB2 comes with support for background images and bitmap fonts in pf2 format. The unifont font is included in the grub2 package under the filename {{ic|unicode.pf2}}, or, as only ascii characters under the name {{ic|ascii.pf2}}.  

Make sure you have set up the proper [https://wiki.archlinux.org/index.php/GRUB2#Setting_the_framebuffer_resolution framebuffer resolution].

  GRUB_BACKGROUND="/boot/grub/archlinux.tga"

(archlinux.tga is a placeholder; put your file name there)

 

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

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.

* The path and the filename in /etc/default/grub are correct.

* 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.

As in Grub (0.9x), you can change the menu colors in Grub2. The available colors for GRUB2 are at http://www.gnu.org/software/grub/manual/html_node/Theme-file-format.html#Theme-file-format.

One of the unique features of Grub2 is hiding/skipping the menu and showing it by holding "Shift" when needed. You can also adjust whether you want to see the timeout counter.

  set root=(''lvm_group_name''-''lvm_logical_boot_partition_name'')

  set root=(VolumeGroup-lv_boot)

==== Raid ====

Grub2 provides convenient handling of raid-volumes. You need to add:

insmod raid

 

which allows you to address the volume natively. E.g. {{ic|/dev/md0}} becomes:

whereas a partitioned raid-volume (e.g. {{ic|/dev/md0p1}}) becomes:

You can use UUIDs to detect partitions instead of the "old" {{ic|/dev/sd*}} and {{ic|/dev/hd*}} scheming. It has the advantage of detecting partitions by their unique UUIDs, which is needed by some people booting with complicated partition setups.

UUIDs are used by default in the recent versions of grub2 - there is no downside in it anyway except that you need to re-generate the {{ic|grub.cfg}} file every time you resize or reformat your partitions. Remember this when modifying partitions with Live-CD.

The recent versions of grub2 use UUIDs by default. You can re-enable the use of UUIDS by simply commenting the UUID line (this is also what it looks like by default):

you can also just set the value as {{ic|false}} as shown here:

GRUB_DISABLE_LINUX_UUID=false

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

  # tune2fs -L a <LABEL> <PARTITION>

     search --label --no-floppy --set=root archroot

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}}:

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}}:

Note that manually added menu items, eg Windows in {{ic|/etc/grub.d/40_custom}}, will need {{ic|savedefault}} added. Remember to regenerate your configuration file.

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:

where <password> is the string generated by {{ic|grub-mkpasswd_pbkdf2}}.

Regenerate your configuration file. Your GRUB2 command line and boot parameters are now protected.

=== Booting an Ubuntu ISO Image from the GRUB2 Screen ===

  menuentry "ubuntu-11.04-desktop-amd64.iso" {

set isofile="/path/to/ubuntu-11.04-desktop-amd64.iso"

loopback loop (hdX,Y)$isofile

linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile quiet noeject noprompt splash --

initrd (loop)/casper/initrd.lz

Be sure to adjust the "hdX,Y" in the third line to point to the correct disk/partition number of the isofile.  When finished, update grub2's configuration file via:

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

  grub rescue> insmod (hdX,Y)/boot/grub/normal.mod

* [http://kde-apps.org/content/show.php?content=139643 grub2-editor] (requires kdelibs)

* [http://kde-apps.org/content/show.php?content=137886 kcm-grub2] (requires kdelibs python2-qt kdebindings-python)

* [http://sourceforge.net/projects/startup-manager/ startupmanager] (requires gnome-python imagemagick yelp python2 xorg-xrandr)

== parttool or legacy hide/unhide ==

If you have a win9x paradigm with hidden C disks GRUB legacy had the hide/unhide feature. In GRUB2 this has been replaced by parttool. For example, to boot the third C disk of three win9x installations on the CLI enter the CLI and:

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.

To expand console capabilities, insert the "linux" module:

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

After successfully booting the Arch Linux installation, users can correct {{ic|grub.cfg}} as needed and then run:

== Combining the use of UUID's and basic scripting ==

If you like the idea of using UUID's to avoid unreliable BIOS mappings or are struggling with Grub's syntax, here is an example boot menu item that uses UUID's and a small script to direct Grub to the proper disk partitions for your system. All you need to do is replace the UUID's in the sample with the correct UUID's 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.)

    #Enter the UUID of your boot partition (this is where Grub and your kernel reside)

    set uuid_grub_boot=ece0448f-bb08-486d-9864-ac3271bd8d07

    #Enter the UUID of the partition containing the root partition of your Arch Linux installation.           

    #(Note: this may be the same as your boot partition)

    #Here we set the Grub "root" variable by locating the UUID of the root partition identified above 

    search --fs-uuid --no-floppy --set=root $uuid_os_root

    # $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

Add

If you get this error when booting any menuentry

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 {{ic|/usr/share/grub/unicode.pf2}} to ${GRUB2_PREFIX_DIR} ({{ic|/boot/grub/}} in case of BIOS systems and {{ic|/boot/efi/efi/grub/}} in case of UEFI systems).

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}.

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

UEFI systems

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

  if loadfont ${prefix}/unicode.pf2

As you can see for gfxterm (graphical terminal) to function properly, {{ic|unicode.pf2}} font file should exist in ${GRUB2_PREFIX_DIR}.

This error may occur when you try installing GRUB2 in a VMware container. Read more about it [http://bbs.archlinux.org/viewtopic.php?pid=581760#p581760 here]. It happens when the first partition starts just after the MBR (block 63), without the usual space of 1 MiB (2048 blocks) before the first partition. Read [[#MBR_aka_msdos_partitioning_specific_instructions]]

If grub loads but drop you into the rescue shell with no errors, it may be because of a missing or misplaced {{ic|grub.cfg}}. For UEFI, {{ic|grub.cfg}} must be copied into the UEFI system partition alongside grub.efi ({{ic|/boot/efi/EFI/grub}})

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

  Boot0002* Festplatte BIOS(2,0,00)P0: SAMSUNG HD204UI           .

If everything works correctly, the EFI would now automatically load grub.<br>

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:

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.

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

# Official GRUB2 Manual - http://www.gnu.org/software/grub/manual/grub.html

# Ubuntu wiki page for Grub2 - https://help.ubuntu.com/community/Grub2