grub-btrfs improves the grub bootloader by adding a btrfs snapshots sub-menu, allowing the user to boot into snapshots.

grub-btrfs supports manual snapshots as well as snapper, timeshift, and yabsnap created snapshots.

If you wish to use read-only snapshots, /var/log or even /var must be on a separate subvolume. Otherwise, make sure your snapshots are writable. See this ticket for more info.

This project includes its own solution. Refer to the documentation.

• Automatically lists snapshots existing on the btrfs root partition.
• Automatically detect if /boot is in a separate partition.
• Automatically detect kernel, initramfs and Intel/AMD microcode in /boot directory within snapshots.
• Automatically create corresponding menu entries in grub.cfg
• Automatically detect the type/tags/triggers and descriptions/comments of Snapper/Timeshift/Yabsnap snapshots.
• Automatically generate grub.cfg if you use the provided Systemd/ OpenRC service.

The package is available in the extra repository grub-btrfs

pacman -S grub-btrfs

grub-btrfs is only available in the Gentoo User Repository (GURU) and not in the official Gentoo repository.
If you have not activated the GURU yet, do so by running:

emerge -av app-eselect/eselect-repository 
eselect repository enable guru 
emaint sync -r guru 

If you are using Systemd on Gentoo, make sure the USE-Flag systemd is set. (Either globally in make.conf or in package.use for the package app-backup/grub-btrfs) Without Systemd USE-Flag the OpenRC-daemon of grub-btrfs will be installed.

Emerge grub-btrfs via emerge app-backup/grub-btrfs

grub-btrfs is available in the Kali Linux repository and can be installed with:

apt install grub-btrfs

Booting into read-only snapshots is fully supported when choosing btrfs as the file system during a standard Kali Linux installation following this walk-through.

• Run make install
• Run make help to check what options are available.
• Dependencies:
  • btrfs-progs
  • grub
  • bash >4
  • gawk
  • (only when using the grub-btrfsd daemon)inotify-tools

To manually generate grub snapshot entries you can run sudo /etc/grub.d/41_snapshots-btrfs which updates grub-btrfs.cfg. You then need to regenerate the GRUB configuration by running one of the following commands:

• On Arch Linux or Gentoo use grub-mkconfig -o /boot/grub/grub.cfg.
• On Fedora use grub2-mkconfig -o /boot/grub2/grub.cfg
• On Debian and Ubuntu based distributions update-grub is a script that runs grub-mkconfig ...

This process can be automated to occur whenever you create or delete snapshots but this process is slightly different depending upon your distributions choice on init system. See the relevant instructions for your init system below.

You have the possibility to modify many parameters in /etc/default/grub-btrfs/config. For further information see config file or man grub-btrfs

Some file locations and command names differ from distribution to distribution. Initially the configuration is set up to work with Arch and Gentoo (and many other distributions) out of the box, which are using the grub-mkconfig command. However Fedora, for example, uses a different command, grub2-mkconfig. Edit the GRUB_BTRFS_MKCONFIG variable in /etc/default/grub-btrfs/config file to reflect this. (e.g. GRUB_BTRFS_MKCONFIG=/sbin/grub2-mkconfig for Fedora)

On most distributions, the grub installation resides in /boot/grub. If grub is installed in a different place, change the variable GRUB_BTRFS_MKCONFIG in the config file accordingly. For Fedora this is GRUB_BTRFS_GRUB_DIRNAME="/boot/grub2". The command to check the grub scripts is different on some system, for Fedora it is GRUB_BTRFS_SCRIPT_CHECK=grub2-script-check

Grub-btrfs comes with a daemon script that automatically updates the grub menu when it sees a snapshot being created or deleted in a directory it is given via command line. You must install inotify-tools before you can use grub-btrfsd.

The daemon can be configured by passing different command line arguments to it. The available arguments are:

• SNAPSHOTS_DIRS This argument specifies the (space separated) paths where grub-btrfsd looks for newly created snapshots and snapshot deletions. It is usually defined by the program used to make snapshots. E.g. for Snapper or Yabsnap this would be /.snapshots. It is possible to define more than one directory here, all directories will inherit the same settings (recursive etc.). This argument is not necessary to provide if --timeshift-auto is set.
• -c / --no-color Disable colors in output.
• -l / --log-file This arguments specifies a file where grub-btrfsd should write log messages.
• -r / --recursive Watch the snapshots directory recursively
• -s / --syslog
• -o / --timeshift-old Look for snapshots in /run/timeshift/backup/timeshift-btrfs instead of /run/timeshift/$PID/backup/timeshift-btrfs. This is to be used for Timeshift versions <22.06. You must also use --timeshift-auto if using this option.
• -t / --timeshift-auto This is a flag to activate the auto-detection of the path where Timeshift stores snapshots. Newer versions (>=22.06) of Timeshift mount their snapshots to /run/timeshift/$PID/backup/timeshift-btrfs. Where $PID is the process ID of the currently running Timeshift session. The PID changes every time Timeshift is opened. grub-btrfsd can automatically take care of the detection of the correct PID and directory if this flag is set. In this case the argument SNAPSHOTS_DIRS has no effect.
• -v / --verbose Let the log of the daemon be more verbose
• -h / --help Displays a short help message.

Grub-btrfsd is a daemon that watches the snapshot directory for you and updates the grub menu automatically every time a snapshot is created or deleted. By default this daemon watches the directory /.snapshots for changes (creation or deletion of snapshots) and triggers the grub menu creation and re-installation of grub if any changes are noticed. Therefore, if Snapper or Yabsnap is used with its default directory, the daemon can just be started and nothing needs to be configured. See the instructions below to configure grub-btrfsd for use with Timeshift or when using an alternative snapshots directory with Snapper/Yabsnap.

To start the daemon run:

sudo systemctl start grub-btrfsd

To activate it during system startup, run:

sudo systemctl enable grub-btrfsd

By default the daemon is watching the directory /.snapshots. If the daemon should watch a different directory, it can be edited with:

sudo systemctl edit --full grub-btrfsd 

You need to edit the /.snapshots part in the line that says ExecStart=/usr/bin/grub-btrfsd --syslog /.snapshots. This is what the file should look like afterwards:

[Unit]
Description=Regenerate grub-btrfs.cfg

[Service]
Type=simple
LogLevelMax=notice
# Set the possible paths for `grub-mkconfig`
Environment="PATH=/sbin:/bin:/usr/sbin:/usr/bin"
# Load environment variables from the configuration
EnvironmentFile=/etc/default/grub-btrfs/config
# Start the daemon, usage of it is:
# grub-btrfsd [-h, --help] [-t, --timeshift-auto] [-l, --log-file LOG_FILE] SNAPSHOTS_DIRS
# SNAPSHOTS_DIRS         Snapshot directories to watch, without effect when --timeshift-auto
# Optional arguments:
# -t, --timeshift-auto  Automatically detect Timeshifts snapshot directory
# -o, --timeshift-old   Activate for timeshift versions <22.06
# -l, --log-file        Specify a logfile to write to
# -v, --verbose         Let the log of the daemon be more verbose
# -s, --syslog          Write to syslog
ExecStart=/usr/bin/grub-btrfsd --syslog /.snapshots

[Install]
WantedBy=multi-user.target

When done, the service should be restarted with:

sudo systemctl restart grub-btrfsd 

Newer Timeshift versions (>= 22.06) create a new directory named after their process ID in /run/timeshift every time they are started. The PID will be different every time. Therefore the daemon cannot simply watch a directory. It monitors /run/timeshift and if a directory is created it gets Timeshifts current PID then watches a directory in that newly created directory from Timeshift. To activate this mode of the daemon, --timeshift-auto must be passed to the daemon as a command line argument.

To pass --timeshift-auto to grub-btrfsd, the .service file of grub-btrfsd can be edited with

sudo systemctl edit --full grub-btrfsd 

The line that contains:

ExecStart=/usr/bin/grub-btrfsd /.snapshots --syslog

Should be modified to read:

ExecStart=/usr/bin/grub-btrfsd --syslog --timeshift-auto

The modified file should look like this:

[Unit]
Description=Regenerate grub-btrfs.cfg

[Service]
Type=simple
LogLevelMax=notice
# Set the possible paths for `grub-mkconfig`
Environment="PATH=/sbin:/bin:/usr/sbin:/usr/bin"
# Load environment variables from the configuration
EnvironmentFile=/etc/default/grub-btrfs/config
# Start the daemon, usage of it is:
# grub-btrfsd [-h, --help] [-t, --timeshift-auto] [-l, --log-file LOG_FILE] SNAPSHOTS_DIRS
# SNAPSHOTS_DIRS         Snapshot directories to watch, without effect when --timeshift-auto
# Optional arguments:
# -t, --timeshift-auto  Automatically detect Timeshifts snapshot directory
# -l, --log-file        Specify a logfile to write to
# -v, --verbose         Let the log of the daemon be more verbose
# -s, --syslog          Write to syslog
ExecStart=/usr/bin/grub-btrfsd --syslog --timeshift-auto

[Install]
WantedBy=multi-user.target

If you are using an older release of Timeshift (before 22.06), you also need to add --timeshift-old so that your ExecStart line would look like:

ExecStart=/usr/bin/grub-btrfsd --syslog --timeshift-auto --timeshift-old

When done, the service must be restarted with:

sudo systemctl restart grub-btrfsd 

Note: You can view your change with systemctl cat grub-btrfsd. To revert all the changes use systemctl revert grub-btrfsd.

To start the daemon run:

sudo rc-service grub-btrfsd start 

To activate it during system startup, run:

sudo rc-config add grub-btrfsd default 

By default the daemon is watching the directory /.snapshots. If the daemon should watch a different directory, it can be edited by passing different arguments to it. Arguments are passed to grub-btrfsd via the file /etc/conf.d/grub-btrfsd. The variable snapshots defines the path the daemon will monitor for snapshots.

After editing, the file should look like this:

# Copyright 2022 Pascal Jaeger
# Distributed under the terms of the GNU General Public License v3

## Where to locate the root snapshots
snapshots="/.snapshots" # Snapper in the root directory
#snapshots="/run/timeshift/backup/timeshift-btrfs/snapshots" # Timeshift < v22.06

## Optional arguments to run with the daemon
# Append options to this like this:
# optional_args="--syslog --timeshift-auto --verbose"
# Possible options are:
# -t, --timeshift-auto  Automatically detect Timeshifts snapshot directory for timeshift >= 22.06
# -o, --timeshift-old   Look for snapshots in directory of Timeshift <v22.06 (requires --timeshift-auto)
# -l, --log-file        Specify a logfile to write to
# -v, --verbose         Let the log of the daemon be more verbose
# -s, --syslog          Write to syslog
optional_args="--syslog"

After that, the daemon should be restarted with:

sudo rc-service grub-btrfsd restart

If you experience problems with grub-btrfs don't hesitate to file an issue.

When requesting help or reporting bugs in grub-btrfs, please run:

sudo /etc/grub.d/41_snapshots-btrfs --version

or

sudo /usr/bin/grub-btrfsd --help

to get the currently running version of grub-btrfs and include this information in your ticket.

If you have problems with the daemon, you can run it with the --verbose-flag. To do so you can run:

sudo /usr/bin/grub-btrfsd --verbose --timeshift-auto` (for timeshift)
# or 
sudo /usr/bin/grub-btrfsd /.snapshots --verbose` (for snapper/yabsnap)

Or pass --verbose to the daemon using the Systemd .service file or the OpenRC conf.d file respectively.

For additional information on the daemon and its arguments, run grub-btrfsd -h or man grub-btrfsd

Grub-btrfs uses a rudimentary system of automatic versioning to tell apart different commits. This is helpful when users report problems and it is not immediately clear what version they are using. We therefore have the following script in .git/hooks/pre-commit:

#!/bin/sh

echo "Doing pre commit hook with version bump"
version="$(git describe --tags --abbrev=0)-$(git rev-parse --abbrev-ref HEAD)-$(date -u -Iseconds)"
echo "New version is ${version}"
sed -i "s/GRUB_BTRFS_VERSION=.*/GRUB_BTRFS_VERSION=${version}/" config
git add config

This automatically sets the version in the config-file to [lasttag]-[branch-name]-[current-date-in-UTC]. In order to create a Tag we don't want to have this long version. In this case we set the version manually in config and commit with git commit --no-verify. This avoids running the hook.

• Maxim Baz
• Schievel1
• All contributors