|Summary help replacing me|
|Covers various aspects of Arch Linux's default bootloader, the GRand Unified Bootloader (GRUB).|
|Template:Boot process overview|
GRUB Legacy is a multiboot bootloader previously maintained by the GNU Project. It was derived from GRUB, the GRand Unified Bootloader, which was originally designed and implemented by Erich Stefan Boleyn.
Briefly, 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.
- 1 Installation
- 2 Upgrading to GRUB2
- 3 Bootloader installation
- 4 Tips and tricks
- 4.1 Graphical boot
- 4.2 Framebuffer resolution
- 4.3 Naming partitions
- 4.4 Boot as root (single-user mode)
- 4.5 Password protection
- 4.6 Restart with named boot choice
- 4.7 LILO and GRUB interaction
- 4.8 GRUB boot disk
- 4.9 Hide GRUB menu
- 5 Advanced Debugging
- 6 Troubleshooting
- 7 See also
Additionally, GRUB must be installed to the boot sector of a drive or partition to serve as a bootloader. This is covered in the #Bootloader installation section.
Upgrading to GRUB2
Is upgrading necessary?
The short answer is No. GRUB legacy will not be removed from your system and will stay fully functional.
How to upgrade
- FRAMEBUFFER RESOLUTION SETTINGS
- | 640x480 800x600 1024x768 1280x1024
- 256 | 0x301=769 0x303=771 0x305=773 0x307=775
- 32K | 0x310=784 0x313=787 0x316=790 0x319=793
- 64K | 0x311=785 0x314=788 0x317=791 0x31A=794
- 16M | 0x312=786 0x315=789 0x318=792 0x31B=795
- for more details and different resolutions see
Manual recovery of GRUB libs
*stage* files are expected to be in
/boot/grub, which may not be the case if the bootloader was not installed during system installation or if the partition/filesystem was damaged, accidentally deleted, etc.
Manually copy the GRUB libs like so:
# cp -a /usr/lib/grub/i386-pc/* /boot/grub
General notes about bootloader installation
GRUB may be installed from a separate medium (e.g. a LiveCD), or directly from a running Arch install. The GRUB bootloader is seldom required to be reinstalled and installation is not necessary when:
- The configuration file is updated.
- The package is updated.
Installation is necessary when:
- A bootloader is not already installed.
- Another operating system overwrites the Linux bootloader.
- The bootloader fails for some unknown reason.
Before continuing, a few notes:
- Be sure that your GRUB configuration is correct (
/boot/grub/menu.lst) before proceeding. Refer to #Finding GRUB's root to ensure your devices are defined correctly.
- GRUB must be installed on the MBR (first sector of the hard disk), or the first partition of the first storage device to be recognized by most BIOSes. To allow individual distributions the ability to manage their own GRUB menus, multiple instances of GRUB can be used, see #chainloader and configfile.
- Installing the GRUB bootloader may need to be done from within a
chrooted environment (i.e. from installed environment via a separate medium) for cases like RAID configurations or if you forgot/broke your GRUB installation. You will need to Change Root from a LiveCD or another Linux installation to do so.
First, enter the GRUB shell:
root command with the output from the
find command (see #Finding GRUB's root) to instruct GRUB which partition contains stage1 (and therefore,
grub> root (hd1,0)
Installing to the MBR
The following example installs GRUB to the MBR of the first drive:
grub> setup (hd0)
Installing to a partition
The following example installs GRUB to the first partition of the first drive:
grub> setup (hd0,0)
quit to exit the shell. If you chrooted, exit your chroot and unmount partitions. Now reboot to test.
Alternate method (grub-install)
grub-install command followed by the location to install the bootloader. For example to install the GRUB bootloader to the MBR of the first drive:
# grub-install /dev/sda
GRUB will indicate whether it successfully installs. If it does not, you will have to use the GRUB shell method.
Tips and tricks
Additional configuration notes.
One can use the resolution given in the
menu.lst, but you might want to use your LCD wide-screen at its full native resolution. Here is what you can do to achieve this:
On Wikipedia, there is a list of extended framebuffer resolutions (i.e. beyond the ones in the VBE standard). But, for example, the one I want to use for 1440x900 (
vga=867) does not work. This is because the graphic card manufacturers are free to choose any number they wish, as this is not part of the VBE 3 standard. This is why these codes change from one card to the other (possibly even for the same manufacturer).
So instead of using that table, you can use one of the tools mentioned below to get the correct code:
GRUB recognized value
This is an easy way to find the resolution code using only GRUB itself.
On the kernel line, specify that the kernel should ask you which mode to use.
kernel /vmlinuz-linux root=/dev/sda1 ro vga=ask
Now reboot. GRUB will now present a list of suitable codes to use and the option to scan for even more.
You can pick the code you would like to use (do not forget it, it is needed for the next step) and boot using it.
ask in the kernel line with the correct one you have picked.
e.g. the kernel line for
 1680x1050x32 would be:
kernel /vmlinuz-linux root=/dev/sda1 ro vga=0x369
- Install from [community].
hwinfo --framebufferas root.
- Pick up the code corresponding to the desired resolution.
- Use the 6 digit code with 0x prefix in
vga=kernel option in
menu.lst. Or convert it to decimal to avoid the use of 0x prefix.
Example output of hwinfo:
Mode 0x0364: 1440x900 (+1440), 8 bits Mode 0x0365: 1440x900 (+5760), 24 bits
And the kernel line:
kernel /vmlinuz-linux root=/dev/sda1 ro vga=0x0365
- Install the AUR that contains the vbetest tool (x86_64 users will need to use #hwinfo above). AUR package from the
- Then note the number in [ ] corresponding to your desired resolution.
- Press 'q' to quit vbetest interactive prompt.
- As an option, in a console as root, you can test the mode you just picked up by running
vbetest -m <yourcode>and see a pattern like this one
- As an option, in a console as root, you can test the mode you just picked up by running
- Add 512 to the discovered value picked up above and use the total value to define the
vga=parameter in the kernel options of
- Reboot to enjoy the result
For example vbetest on one computer:
 1440x900 (256 color palette)  1440x900 (8:8:8)
So here the number you want is 357. Then, 357 + 512 = 869, so you will use vga=869. Add your value to the end of the kernel line in
menu.lst as shown below:
kernel /vmlinuz-linux root=/dev/sda1 ro vga=869
If you alter (or plan to alter) partition sizes from time to time, you might want to consider defining your drive/partitions by a label. You can label ext2, ext3, ext4 partitions by:
e2label </dev/drive|partition> label
The label name can be up to 16 characters long but cannot have spaces for GRUB to understand it. Then define it in your
kernel /boot/vmlinuz-linux root=/dev/disk/by-label/Arch_Linux ro
The UUID (Universally Unique IDentifier) of a partition may be discovered with
ls -l /dev/disk/by-uuid. It is defined in
menu.lst with either:
kernel /boot/vmlinuz-linux root=/dev/disk/by-uuid/<uuid number>
kernel /boot/vmlinuz-linux root=UUID=<uuid number>
Boot as root (single-user mode)
At the boot loader, select an entry and edit it ('e' key). Append the following parameters to the kernel options:
[...] single init=/bin/bash
This will start in single-user mode (init 1), i.e. you will end up to a root prompt without being asked for password. This may be useful for recovery features, like resetting the root password. However, this is a huge security flaw if you have not set any password protection for grub.
You can enable password protection in the GRUB configuration file for operating systems you wish to have protected. Bootloader password protection may be desired if your BIOS lacks such functionality and you need the extra security.
First, choose a password you can remember and then encrypt it:
# grub-md5-crypt Password: Retype password: $1$ZOGor$GABXUQ/hnzns/d5JYqqjw
Then add your password to the beginning of the GRUB configuration file at
/boot/grub/menu.lst (the password must be at the beginning of the configuration file for GRUB to be able to recognize it):
# general configuration timeout 5 default 0 color light-blue/black light-cyan/blue password --md5 $1$ZOGor$GABXUQ/hnzns/d5JYqqjw
Then for each operating system you wish to protect, add the
# (0) Arch Linux title Arch Linux lock root (hd0,1) kernel /boot/vmlinuz-linux root=/dev/disk/by-label/Arch_Linux ro initrd /boot/initramfs-linux.img
It is always possible to reset your BIOS settings by setting the appropriate jumper on the motherboard (see your motherboard's manual, as it is specific to every model). So in case other have access to the hardware, there is basically no way to prevent boot breakthroughs.
Restart with named boot choice
If you realize that you often need to switch to some other non-default OS (e.g. Windows) having to reboot and wait for the GRUB menu to appear is tedious. GRUB offers a way to record your OS choice when restarting instead of waiting for the menu, by designating a temporary new default which will be reset as soon as it has been used.
Supposing a simple
menu.lst setup like this:
# general configuration: timeout 10 default 0 color light-blue/black light-cyan/blue # (0) Arch title Arch Linux root (hd0,1) kernel /boot/vmlinuz-linux root=/dev/disk/by-label/ARCH ro initrd /boot/initramfs-linux.img # (1) Windows title Windows XP rootnoverify (hd0,0) makeactive chainloader +1
Arch is the default (0). We want to restart in to Windows. Change
default 0 to
default saved -- this will record the current default in a
default file in the GRUB directory whenever the savedefault command is used. Now add the line
savedefault 0 to the bottom of the Windows entry. Whenever Windows is booted, it will reset the default to Arch, thus making changing the default to Windows temporary.
Now all that is needed is a way to easily change the default manually. This can be accomplished using the command
grub-set-default. So, to reboot into Windows, enter the following command:
$ sudo grub-set-default 1 && sudo shutdown -r now
For ease of use, you might to wish to implement the "Allow users to shutdown fix" (including
/sbin/grub-set-default amongst the commands the user is allowed to issue without supplying a password).
LILO and GRUB interaction
If the LILO package is installed on your system, remove it with
# pacman -R lilo
as some tasks (e.g. kernel compilation using
make all) will make a LILO call, and LILO will then be installed over GRUB. LILO may have been included in your base system, depending on your installer media version and whether you selected/deselected it during the package selection stage.
GRUB boot disk
First, format a floppy disk:
fdformat /dev/fd0 mke2fs /dev/fd0
Now mount the disk:
mount -t ext2 /dev/fd0 /mnt/fl
Install GRUB to the disk:
grub-install --root-directory=/mnt/fl '(fd0)'
menu.lst file to the disk:
cp /boot/grub/menu.lst /mnt/fl/boot/grub/menu.lst
Now unmount your floppy:
Now you should be able to restart your computer with the disk in the drive and it should boot to GRUB. Make sure that your floppy disk is set to have higher priority than your hard drive when booting in your BIOS first, of course.
See also: Super GRUB Disk
hiddenmenu option can be used in order to hide the menu by default. That way no menu is displayed and the default option is going to be automatically selected after the timeout passes.
Still, you are able to press Template:Keypress and the menu shows up. To use it, just add to your
Content moved to Boot_Debugging
GRUB Error 17
The first check to do is to unplug any external drive. Seems obvious, but sometimes we get tired ;)
If your partition table gets messed up, an unpleasant "GRUB error 17" message might be the only thing that greets you on your next reboot. There are a number of reasons why the partition table could get messed up. Commonly, users who manipulate their partitions with GParted -- particularly logical drives -- can cause the order of the partitions to change. For example, you delete
/dev/sda6 and resize
/dev/sda7, then finally re-create what used to be
/dev/sda6 only now it appears at the bottom of the list,
/dev/sda9 for example. Although the physical order of the partitions/logical drives has not changed, the order in which they are recognized has changed.
Fixing the partition table is easy. Boot from your Arch CD/DVD/USB, login as root and fix the partition table:
# fdisk /dev/sda
Once in disk, enter e[x]tra/expert mode, [f]ix the partition order, then [w]rite the table and exit.
You can verify that the partition table was indeed fixed by issuing an
fdisk -l. Now you just need to fix GRUB. See the #Bootloader installation section above.
Basically you need to tell GRUB the correct location of your
/boot then re-write GRUB to the MBR on the disk.
grub> root (hd0,6) grub> setup (hd0) grub> quit
See [this page] for a more in-depth summary of this section.
/boot/grub/stage1 not read correctly
If you see this error message while trying to set up GRUB, and you are not using a fresh partition table, it is worth checking it.
# fdisk -l /dev/sda
This will show you the partition table for
/dev/sda. So check here, whether the "Id" values of your partitions are correct.
The "System" column will show you the description of the "Id" values.
If your boot partition is marked as being "HPFS/NTFS", for example, then you have to change it to "Linux". To do this, go to fdisk,
# fdisk /dev/sda
change a partition's system id with [t], select you partition number and type in the new system id (Linux = 83). You can also list all available system ids by typing "L" instead of a system id.
If you have changed a partitions system id, you should [v]erify your partition table and then [w]rite it.
Now try to set up GRUB again.
[Here] is the forum post reporting this problem.
Accidental install to a Windows partition
If you accidentally install GRUB to a Windows partition, GRUB will write some information to the boot sector of the partition, erasing the reference to the Windows bootloader. (This is true for NTLDR the bootloader for Windows XP and earlier, unsure about later versions).
To fix this you will need to use the Windows Recovery Console for your Windows release. Because many computer manufacturers do not include this with their product (many choose to use a recovery partition) Microsoft has made them available for download. If you use XP, look at this page to be able to turn the floppy disks to a Recovery CD. Boot the Recovery CD (or enable Windows Recovery mode) and run
fixboot to repair the partition boot sector. After this, you will have to install GRUB again---this time, to the MBR, not to the Windows partition---to boot Linux.
Once you have selected and entry in the boot menu, you can edit it by pressing key Template:Keypress. Use tab-completion if you need to to discover devices then Template:Keypress to exit. Then you can try to boot by pressing Template:Keypress.
If an error is raised mentioning
/boot/grub/device.map during installation or boot, run:
# grub-install --recheck /dev/sda
to force GRUB to recheck the device map, even if it already exists. This may be necessary after resizing partitions or adding/removing drives.
If you have opened a sub-menu with the list of all operating systems configured in GRUB, selected one, and upon restart, you still booted your default OS, then you might want to check if you have the line:
GRUB fails to find or install to any virtio /dev/vd* or other non-BIOS devices
I had trouble installing GRUB while installing Arch Linux in an virtual KVM machine using a virtio device for hard drive. To install GRUB, I figured out the following:
Enter a virtual console by typing Template:Keypress or any other F-key for a free virtual console.
This assumes that your root file system is mounted in the folder
/mnt and the boot file system is either mounted or stored in the folder
1. Assure that all needed GRUB files is present in your boot directory (assuming it is mounted in
/mnt/boot folder), by issuing the command:
# ls /mnt/boot/grub
2. If the
/mnt/boot/grub folder already contains all the needed files, jump to step 3. Otherwise, do the following commands (replacing
your_initrd with the real paths and file names). You should also have the
menu.lst file written to this folder:
# mkdir -p /mnt/boot/grub # if the folder is not yet present # cp -r /boot/grub/stage1 /boot/grub/stage2 /mnt/boot/grub # cp -r your_kernel your_initrd /mnt/boot
3. Start the GRUB shell with the following command:
# grub --device-map=/dev/null
4. Enter the following commands. Replace
(hd0,0) with the correct device and partition corresponding to your setup.
device (hd0) /dev/vda root (hd0,0) setup (hd0) quit
5. If GRUB reports no error messages, then you probably are done. You also need to add appropriate modules to the ramdisk. For more information, please refer to the KVM guide on Preparing an (Arch) Linux guest