Backing up a LXD server

What to backup

When planning to backup a LXD server, consider all the different objects that are stored/managed by LXD:

  • Instances (database records and filesystems)
  • Images (database records, image files and filesystems)
  • Networks (database records and state files)
  • Profiles (database records)
  • Storage volumes (database records and filesystems)

Only backing up the database or only backing up the instances will not get you a fully functional backup.

In some disaster recovery scenarios, that may be reasonable but if your goal is to get back online quickly, consider all the different pieces of LXD you're using.

Full backup

A full backup would include the entirety of /var/lib/lxd or /var/snap/lxd/common/lxd for snap users.

You will also need to appropriately backup any external storage that you made LXD use, this can be LVM volume groups, ZFS zpools or any other resource which isn't directly self-contained to LXD.

Restoring involves stopping LXD on the target server, wiping the lxd directory, restoring the backup and any external dependency it requires.

Then start LXD again and check that everything works fine.

Secondary backup LXD server

LXD supports copying and moving instances and storage volumes between two hosts.

So with a spare server, you can copy your instances and storage volumes to that secondary server every so often, allowing it to act as either an offline spare or just as a storage server that you can copy your instances back from if needed.

Instance backups

The lxc export command can be used to export instances to a backup tarball. Those tarballs will include all snapshots by default and an "optimized" tarball can be obtained if you know that you'll be restoring on a LXD server using the same storage pool backend.

You can use any compressor installed on the server using the --compression flag. There is no validation on the LXD side, any command that is available to LXD and supports -c for stdout should work.

Those tarballs can be saved any way you want on any filesystem you want and can be imported back into LXD using the lxc import command.

Disaster recovery

Additionally, LXD maintains a backup.yaml file in each instance's storage volume. This file contains all necessary information to recover a given instance, such as instance configuration, attached devices and storage.

This file can be processed by the lxd import command, not to be confused with lxc import.

To use the disaster recovery mechanism, you must mount the instance's storage to its expected location, usually under storage-pools/NAME-OF-POOL/containers/NAME-OF-CONTAINER.

Depending on your storage backend you will also need to do the same for any snapshot you want to restore (needed for dir and btrfs).

Once everything is mounted where it should be, you can now run lxd import NAME-OF-CONTAINER.

If any matching database entry for resources declared in backup.yaml is found during import, the command will refuse to restore the instance. This can be overridden by passing --force.

NOTE: When dealing with mounts and the snap, you may need to either perform a full restart of the snap with snap stop and snap start or perform the mounts from within the snap environment using nsenter --mount=/run/snapd/ns/lxd.mnt.