btrbk

Resources

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.

Important
btrbk will not create the target directories, it must be created manually.

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 14d 5w 1m 1y
# Preserve the latest snapshot, regardless of the preservation policy
target_preserve_min        latest
# Preserve one archive of each type except hourly backups
archive_preserve           0h 1d 1w 1m 1y
archive_preserve_min       latest

# Backup subvolumes at '/etc', '/var/lib' and '/var/log'
volume /
  target /media/backup/btrbk
  subvolume etc
  subvolume var/lib
  subvolume var/log

Snapshotting subvolumes

Important
This method is not a proper backup as snapshots are stored on the same storage. Backups should be made to another system, or at least another storage device.

FILE /etc/btrbk/btrbk.confMake snapshots of Larry's homedir.

# Create simple snapshots of /home's subvolume 'larry' (replace as appropriate)
# These are not sent to another device or machine (no 'target').
#
# Make sure snapshot_preserve_min / snapshot_preserve are set in the main config section!
volume /home
  snapshot_dir .btrbk_snapshots
  subvolume    larry

Backing up subvolumes

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

FILE /etc/btrbk/btrbk.confBackup the root subvolume to /media/backup/btrbk.

volume /mnt/btr_pool
  target /media/backup/btrbk
  subvolume @root

Backing up standard subvolumes

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

volume /
  target /media/backup/home_backups
  subvolume home

Remote Backups

SSH configuration

Enable and Restrict Root Login

Important
Root login must be enabled on the remote computer 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

Generate keys

Root login should only be performed using keys, not passwords. To generate a new root SSH key, and install it on a target system:

root #

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

root #

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

Backing up to another host using SSH

Backups can be made over SSH:

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 another host using SSH

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.

Usage

Dry run

To do a verbose dry run:

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

Run a full backup

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

root #btrbk run

Create snapshots

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