btrbk

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btrbk(1)

btrbk.conf(5)

btrbk is a tool for creating incremental snapshots and remote backups of Btrfs subvolumes. It is used for simple backups to an external hard drive as well as more complex scenarios, like a server pulling the backups from all computers in the network or just to make local snapshots to protect against accidental deletions.

Terminology

btrbk has terms for the snapshots and backups it creates based on where they're stored and their intended purpose:

• Snapshots are locally (on the same filesystem) stored Btrfs snapshots
• Backups are snapshots copied to a folder or over SSH
• Archives are extra copies of backups.

Installation

root #emerge --ask app-backup/btrbk

Configuration

Tip
A commented example configuration file is found in /etc/btrbk/btrbk.conf.example. Refer to the man page for more details.

To backup subvolumes etc, var/log, and var/lib to /media/backup/btrbk, with snapshots to .btrbk_snapshots:

FILE /etc/btrbk/btrbk.confBasic configuration

# Enable transaction logging
transaction_log            /var/log/btrbk.log
# Use a lockfile so only one btrbk instance can run at a time
lockfile                   /run/lock/btrbk.lock
# Use sudo if btrbk or lsbtr is run by regular user
backend_local_user         btrfs-progs-sudo
# Enable stream buffering 
stream_buffer              256m

# Store snapshots under .btrbk_snapshots under the root of the volume
snapshot_dir               .btrbk_snapshots
# Only create new snapshots when changes have been made
snapshot_create            onchange
# Preserve hourly snapshots for up to 24 hours, and daily snapshots for up to 7 days
snapshot_preserve          24h 7d 0w 0m 0y
# The latest snapshot is always kept, regardless of the preservation policy
snapshot_preserve_min      latest

# Preserve daily backups for up to 14 days, weekly backups for up to 5 weeks, monthly backups for up to a month, and yearly backups for up to a year
target_preserve            0h 7d 5w 4m 1y
# Preserve the latest snapshot, regardless of the preservation policy
target_preserve_min        latest
# Preserve one archive of each type but hourly
archive_preserve           0h 1d 1w 1m 1y
archive_preserve_min       latest

volume /
  target /media/backup/btrbk
  subvolume etc
  subvolume var/lib
  subvolume var/log

Create snapshots for accidental deletion

Note that this particular method is not strictly a backup as it's not stored on another machine.

root #mkdir /home/.btrbk_snapshots

root #btrbk --dry-run --verbose run

FILE /etc/btrbk/btrbk.conf

'"`UNIQ--pre-00000002-QINU`"'

Backing up the root subvolume

To backup the root subvolume, subvolid=5, it must be mounted:

FILE /etc/fstabfstab example with the root subvolume mounted at /mnt/btr_pool

/dev/sda1  /              btrfs  subvol=@root  0 0
/dev/sda1  /mnt/btr_pool  btrfs  subvolid=5    0 0

Create the directory for the snapshots and test the configuration:

root #mkdir /mnt/btr_pool/.btrbk_snapshots

root #btrbk --dry-run --verbose run

FILE /etc/btrbk/btrbk.conf

'"`UNIQ--pre-00000007-QINU`"'

Additional Targets

To backup more targets, add a target:

FILE /etc/btrbk/btrbk.confBackup the home subvolume to /media/backup/home_backups

volume /
  target /media/backup/home_backups
  subvolume home

FILE /etc/btrbk/btrbk.confBackup homedirs to backup.example.org using SSH

ssh_identity               /etc/btrbk/ssh/id_ed25519
ssh_user                   root

volume /
  target ssh://backup.example.org:22/media/backup/home_backups
  subvolume @home

Pull backups from remote computers

This is an example configuration for multiple clients to backup onto a server:

FILE /etc/btrbk/btrbk.conf

ssh_identity               /etc/btrbk/ssh/id_ed25519
ssh_user                   root

volume ssh://larry-desktop.example.org:22/mnt/btr_pool
  target /media/backup/larry-desktop
    subvolume @root
    subvolume @home

volume ssh://larry-laptop.example.org:22/mnt/btr_pool
  target /media/backup/larry-laptop
    subvolume @root

For more examples, take a look at the official documentation hyperlinked at the top right of this page.

SSH configuration

To backup to or from a remote computer via SSH, generate a key and add it to ~root/.ssh/authorized_keys on the targets.

root #ssh-keygen -t ed25519 -f /etc/btrbk/id_ed25519

root #ssh-copy-id -i /etc/btrbk/id_ed25519.pub root@backup.example.org

Note
Enable root login on the remote computer in order for this to work.

FILE /etc/ssh/sshd_config

PermitRootLogin prohibit-password

To restrict the IPs/IP ranges from where root can log in, use the Match keyword. Consult the man page for sshd_config for details.

FILE /etc/ssh/sshd_config

Match Address fd69::6:9
PermitRootLogin prohibit-password
Match All

Usage

To create snapshots and backup (if a target was configured), run:

root #btrbk run

To only create snapshots even if a target is configured, run:

root #btrbk snapshot

Automation with cron

Tip
Don't forget to mark the cron scripts executable:

user $chmod +x /etc/cron.hourly/btrbk-snapshot /etc/cron.daily/btrbk-run

FILE /etc/cron.hourly/btrbk-snapshotLocal snapshots once an hour

#!/bin/sh
exec /usr/bin/btrbk -q snapshot

FILE /etc/cron.daily/btrbk-runBackup once a day

#!/bin/sh
exec /usr/bin/btrbk -q run