ssh_filter_btrbk - ssh command filter script for btrbk

       Axel Burri axel@tty0.ch

Btrbk 0.32.5                                       2022-10-23                                SSH_FILTER_BTRBK(1)

       Please refer to the btrbk project page https://digint.ch/btrbk/ for further details.

ssh_filter_btrbk.sh 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" (not affected by "--restrict-path")

       •   "btrfs subvolume list" (not affected by "--restrict-path")

       •   "readlink"

       •   "test -d" (only if "compat busybox" configuration option is set)

       •   "cat /proc/self/mountinfo"

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

       •   pipes through "mbuffer" (stream_buffer, rate_limit)

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

           command="ssh_filter_btrbk.sh --target --delete --restrict-path /mnt/btr_backup" ssh-rsa AAAAB3NzaC1...hwumXFRQBL btrbk@mydomain.com

       ssh_filter_btrbk - ssh command filter script for btrbk

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

       -t, --target
           Allow commands for backup and archive target: "btrfs receive", "mkdir".

       -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.

       --snapshot
           Allow btrfs snapshot command: "btrfs subvolume snapshot".

       --send
           Allow btrfs send command: "btrfs send".

       --receive
           Allow btrfs receive command: "btrfs receive".

       -p, --restrict-path <path>
           Restrict commands to <path>. Note that "btrfs subvolume show", "btrfs subvolume list" are NOT
           affected by this option.

       -l, --log
           Log ACCEPT and REJECT messages to the system log.

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

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

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