Difference between revisions of "Grub"

Revision as of 08:05, 4 February 2021

Moving boot record and /boot to a new disk

• Setup new disk with GPT partition table
• For BIOS (not EFI) booting, create a ~2MB partition at the start of the disk, with the bios_grub flag

 sudo parted -a optimal -s /dev/sdX -- mklabel gpt mkpart bios 0% 2MB set 1 bios_grub on

• Create a boot partition (but don't set the boot flag)

 sudo parted -a optimal -s /dev/sdX -- mkpart boot 2MB 5GB
 sudo mkfs.ext4 /dev/sdX2

• Use the remainder of the space as desired
• Example "parted /dev/sdX -- print free" for a bootable drive:

Model: ATA ST3320620A (scsi)
Disk /dev/sde: 320GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name  Flags
 1      17.4kB  1049kB  1031kB               bios  bios_grub
 2      1049kB  2000MB  1999MB  ext4         boot
 3      2000MB  320GB   318GB   ext4         tmp
        320GB   320GB   335kB   Free Space

• Mount new boot partition at /mnt, and copy boot partition onto it:

mount /dev/sdXY /mnt
cp -a /boot/* /mnt

• Edit /etc/fstab and change /boot partition mount to UUID for new partition (use /dev/disk/by-uuid to determine partition uuid)
• Unmount existing /boot, and mount new /boot

umount /boot
mount /boot

• Install grub boot loader into the bios partition, using the /boot partition for OS loading. Note that the disk is specified, rather than a partition:

grub-install /dev/sdX

• Update grub to match the new partition layout:

update-grub

• Restart (or halt and disconnect old drive), and cross your fingers!

Updating /boot/grub/device.map

This file is no longer generated (or kept up to date) by default in recent grub versions, since it's largely unused. To update it manually:

 sudo grub-mkdevicemap