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ssh_filter_btrbk - ssh command filter script for btrbk

SYNOPSIS [-s|--source] [-t|--target] [-d|--delete]
    [-i|--info] [--snapshot] [--send] [--receive]
    [-p|--restrict-path <path>] [-l|--log] [--sudo]

DESCRIPTION restricts SSH commands to commands used by btrbk. It examines the SSH_ORIGINAL_COMMAND environment variable (set by sshd) and executes it only if it contains commands used by btrbk.

The accepted commands are specified by the "--source", "--target", "--delete" and "--info" options.

The following commands are always allowed:

•"btrfs subvolume show"

•"btrfs subvolume list"


•"cat /proc/self/mountinfo"

•pipes through "gzip", "pigz", "bzip2", "pbzip2", "xz", "lzop", "lz4" (stream_compress)

•pipes through "mbuffer" (stream_buffer)

•pipes through "pv -L" (rate_limit)

Example line in /root/.ssh/authorized_keys on a backup target host:

command=" --target --delete --restrict-path /mnt/btr_backup" ssh-rsa AAAAB3NzaC1...hwumXFRQBL


-s, --source
Allow commands for backup source: "btrfs subvolume snapshot", "btrfs send". Equivalent to "--snapshot --send".

-t, --target

Allow commands for backup target: "btrfs receive".

-d, --delete

Allow commands for subvolume deletion: "btrfs subvolume delete". This is used for backup source if snapshot_preserve_daily is not set to “all”, and for backup targets if target_preserve_daily is not set to “all”.

-i, --info

Allow informative commands: "btrfs subvolume find-new", "btrfs filesystem usage". This is used by btrbk info and diff commands.


Allow btrfs snapshot command: "btrfs subvolume snapshot".


Allow btrfs send command: "btrfs send".


Allow btrfs receive command: "btrfs receive".

-p, --restrict-path <path>

Restrict btrfs commands to <path>.

-l, --log

Log ACCEPT and REJECT messages to the system log.


Allow btrfs commands to be called via sudo. Enable this if you have "backend btrfs-progs-sudo" in your btrbk configuration file.


Please refer to the btrbk project page <> for further details.


btrbk(1), btrbk.conf(5), btrfs(8)


Axel Burri < <>>
2021-03-23 Btrbk