Btrbk

Btrbk, a tool for creating snapshots and remote backups of btrfs subvolumes.

Setup

When transferring backups of root filesystem snapshots using Btrbk, it is recommended to mount the root Btrfs drive with subvolume id 5 (in this example /dev/sda1) to a specific mountpoint where Btrbk can operate with. So in this case all subvolumes will be available as a subdirectory in /btr_pool.

/etc/nixos/hardware-configuration.nix

fileSystems = {
  "/btr_pool" = {
    device = "/dev/sda1";
    fsType = "btrfs";
    options = [ "subvolid=5" ];
  };
};

Configuration

Following example configuration will create a weekly incremental backup of a local Btrfs subvolume called nixos and sends it compressed to a remote host myhost via ssh using provided authentication credentials. Note that this references the mount point /btr_pool from above.

/etc/nixos/configuration.nix

services.btrbk = {
  extraPackages = [ pkgs.lz4 ];
  instances.remote = {
    onCalendar = "weekly";
    settings = {
      ssh_identity = "/etc/btrbk_key"; # NOTE: must be readable by user/group btrbk
      ssh_user = "btrbk";
      stream_compress = "lz4";
      volume."/btr_pool" = {
        target = "ssh://myhost/mnt/mybackups";
        subvolume = "nixos";
      };
    };
  };
};

For transport stream compression using lz4 to work, the package must also be installed on the target host.

Manual usage

Manually dry running and testing a btrbk configuration

btrbk -c /etc/btrbk/remote.conf --dry-run --progress --verbose run

The filename remote.conf references the instance name choosen in the example configuration above.