Configuration

NAME

grub-btrfs - Automatically add btrfs-Snapshots as a Grub submenu

SYNOPSIS

/etc/grub.d/41_snapshots-btrfs [-V, --version]

DESCRIPTION

Improves grub by adding “btrfs snapshots” to the grub menu.

You can boot your system on a “snapshot” from the grub menu. Supports manual snapshots, snapper and timeshift. Features of grub-btrfs:

Automatically list snapshots existing on root partition (btrfs).

Automatically detect if /boot is in separate partition.

Automatically detect kernel, initramfs and intel/amd microcode in /boot directory on snapshots.

Automatically create corresponding “menuentry” in grub.cfg

Automatically detect the type/tags and descriptions/comments of snapper/timeshift snapshots.

Automatically generate grub.cfg if you use the provided systemd service.

CONFIGURATION

grub-btrfs is configured via the file /etc/default/grub-btrfs/config. Possible options are:

GENERAL

GRUB_BTRFS_DISABLE

Disable grub-btrfs if true.

Default: “false”

Example: GRUB_BTRFS_DISABLE="true"

GRUB_BTRFS_TITLE_FORMAT

The snapshot entries submenu in Grub are added according to this line. It is possible to change to order of the fields.

Default: (“date” “snapshot” “type” “description”)

Example: GRUB_BTRFS_TITLE_FORMAT=("date" "snapshot" "type" "description")

GRUB_BTRFS_LIMIT

Maximum number of snapshots in the GRUB snapshots sub menu.

Default: “50”

Example: GRUB_BTRFS_LIMIT="50"

GRUB_BTRFS_SUBVOLUME_SORT

Sort the found subvolumes by “ogeneration” or “generation” or “path” or “rootid”.

See Sorting section in btrfs-subvolume(8)

“-rootid” means list snapshot by new ones first.

Default: “-rootid”

Example: GRUB_BTRFS_SUBVOLUME_SORT="+ogen,-gen,path,rootid"

GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND

Show snapshots found during run “grub-mkconfig”

Default: “true”

Example: GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND="false"

GRUB_BTRFS_ROOTFLAGS

Comma separated mount options to be used when booting a snapshot. They can be defined here as well as in the “/” line inside the respective snapshots’ “/etc/fstab” files. Mount options found in both places are combined, and this variable takes priority over `fstab` entries.

NB: Do NOT include “subvol=...” or “subvolid=...” here.

Default: ""

Example: GRUB_BTRFS_ROOTFLAGS="space_cache,commit=10,norecovery"

GRUB_BTRFS_OVERRIDE_BOOT_PARTITION_DETECTION

By default “grub-btrfs” automatically detects your boot partition, either located at the system root or on a separate partition or in a subvolume, Change to “true” if your boot partition is not detected as separate.

Default: “false”

Example: GRUB_BTRFS_OVERRIDE_BOOT_PARTITION_DETECTION="true"

CUSTOM KERNELS

GRUB_BTRFS_NKERNEL / GRUB_BTRFS_NINIT / GRUB_BTRFS_CUSTOM_MICROCODE

By default, “grub-btrfs” automatically detects most existing kernels, initramfs and microcode. Customs kernel, initramfs and microcodes that are not detected can be added in these variables.

Default: ("")

Example:

GRUB_BTRFS_NKERNEL=("kernel-5.19.4-custom" "vmlinux-5.19.4-custom")

GRUB_BTRFS_NINIT=("initramfs-5.19.4-custom.img" "initrd-5.19.4-custom.img" "otherinit-5.19.4-custom.gz")

GRUB_BTRFS_CUSTOM_MICROCODE=("custom-ucode.img" "custom-uc.img "custom_ucode.cpio")

GRUB_BTRFS_SNAPSHOT_KERNEL_PARAMETERS

Additional kernel command line parameters that should be passed to the kernelwhen booting a snapshot. For dracut based distros this could be useful to pass “rd.live.overlay.overlayfs=1” or “rd.live.overlay.readonly=1” to the Kernel for booting read only snapshots.

Default: ""

Example: GRUB_BTRFS_SNAPSHOT_KERNEL_PARAMETERS="rd.live.overlay.overlayfs=1"

SNAPSHOT FILTERING

GRUB_BTRFS_IGNORE_SPECIFIC_PATH

Ignore specific path during run “grub-mkconfig”. Only exact paths are ignored. e.g : if `specific path` = @, only `@` snapshot will be ignored.

Default: ("@")

Example: GRUB_BTRFS_IGNORE_SPECIFIC_PATH=("@home")

GRUB_BTRFS_IGNORE_PREFIX_PATH

Ignore prefix path during run “grub-mkconfig”. Any path starting with the specified string will be ignored. e.g : if `prefix path` = @, all snapshots beginning with “@/...” will be ignored.

Default: (“var/lib/docker” “@var/lib/docker” “@/var/lib/docker”)

Example: GRUB_BTRFS_IGNORE_PREFIX_PATH=("var/lib/docker" "@var/lib/docker" "@/var/lib/docker")

GRUB_BTRFS_IGNORE_SNAPSHOT_TYPE

Ignore specific type/tag of snapshot during run “grub-mkconfig”. For snapper: Type = single, pre, post. For Timeshift: Tag = boot, ondemand, hourly, daily, weekly, monthly.

Default: ("")

Example: GRUB_BTRFS_IGNORE_SNAPSHOT_TYPE=("ondemand")

GRUB_BTRFS_IGNORE_SNAPSHOT_DESCRIPTION

Ignore specific description of snapshot during run “grub-mkconfig”.

Default: ("")

Example: GRUB_BTRFS_IGNORE_SNAPSHOT_DESCRIPTION=("timeline")

DISTRIBUTION DEPENDENT SETTINGS

GRUB_BTRFS_BOOT_DIRNAME

Location of kernels/initramfs/microcode. Used by “grub-btrfs” to detect the boot partition and the location of kernels, initramfs and microcodes.

Default: “/boot”

Example: GRUB_BTRFS_BOOT_DIRNAME="/"

GRUB_BTRFS_GRUB_DIRNAME

Location of the folder containing the “grub.cfg” file. Might be grub2 on some systems. For example, on Fedora with EFI : “/boot/efi/EFI/fedora”

Default: “/boot/grub”

Example: GRUB_BTRFS_GRUB_DIRNAME="/boot/grub2"

GRUB_BTRFS_GBTRFS_DIRNAME

Location where grub-btrfs.cfg should be saved. Some distributions (like OpenSuSE) store those file at the snapshot directory instead of boot. Be aware that this directory must be available for grub during startup of the system.

Default: $GRUB_BTRFS_GRUB_DIRNAME

Example: GRUB_BTRFS_GBTRFS_DIRNAME="/.snapshots"

GRUB_BTRFS_GBTRFS_SEARCH_DIRNAME

Location of the directory where Grub searches for the grub-btrfs.cfg file. Some distributions (like OpenSuSE) store those file at the snapshot directory instead of boot. Be aware that this directory must be available for grub during startup of the system.

Default: “${prefix}” (This is a grub variable that resolves to where grub is

installed. (like /boot/grub, /boot/efi/grub))

NOTE: If variables of grub are used here like ${prefix}, they need to be escaped

with `$` before the `$`

Example: GRUB_BTRFS_GBTRFS_SEARCH_DIRNAME="${prefix}"

GRUB_BTRFS_MKCONFIG

Name/path of the command to generate the grub menu, used by “grub-btrfs.service” Might be ‘grub2-mkconfig’ on some systems (e.g. Fedora) Default paths are /sbin:/bin:/usr/sbin:/usr/bin, if your path is missing, report it on the upstream project. You can use the name of the command only or full the path.

Default: grub-mkconfig

Example: GRUB_BTRFS_MKCONFIG=/sbin/grub2-mkconfig

GRUB_BTRFS_SCRIPT_CHECK

Name of grub-script-check command, used by “grub-btrfs” Might be ‘grub2-script-check’ on some systems (e.g. Fedora)

Default: grub-script-check

Example: GRUB_BTRFS_SCRIPT_CHECK=grub2-script-check

GRUB_BTRFS_MKCONFIG_LIB

Path of grub-mkconfiglib file, used by “grub-btrfs” Might be ‘/usr/share/grub2/grub-mkconfiglib’ on some systems (e.g. Opensuse)

Default: /usr/share/grub/grub-mkconfiglib

Example: GRUB_BTRFS_MKCONFIG_LIB=/usr/share/grub2/grub-mkconfig_lib

SECURITY

GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS

Password protection management for submenu, snapshots Refer to the Grub documentation and this commint Add authorized usernames separate by comma (userfoo,userbar). When Grub’s password protection is enabled, the superuser is authorized by default, it is not necessary to add anything.

Default: ""

Example: GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS="userfoo,userbar"

GRUB_BTRFS_DISABLE_PROTECTION_SUBMENU

Disable authentication support for submenu of Grub-btrfs only (--unrestricted) does not work if GRUBBTRFSPROTECTIONAUTHORIZEDUSERS is not empty

Default: “false”

Example: GRUB_BTRFS_DISABLE_PROTECTION_SUBMENU="true"

FILES

/etc/default/grub-btrfs/config

SEE ALSO

btrfs(8) btrfs-subvolume(8) grub-btrfsd(8) grub-mkconfig(8)

COPYRIGHT

Copyright (c) 2022 Pascal Jäger Copyright (c) 2025 Michael Lee Schaecher