Sometimes it is useful, expedient, or desirable to be able to roll back the entire DNS-DHCP LXC container to an earlier state.  This is very useful for example when a VM has been deployed on an Orabuntu-LXC physical host, and then Orabuntu-LXC was deployed in the VM also, and then some subsequent testing and development was done, and now it is desired to update the code and retry the operations.  Because the containers have DNS records in the zone files of the containerized DNS-DHCP, simply restoring a snapshot of the VM will NOT get the system back to the starting state before the operations, because the zone file DNS records still exist in the containerized DNS-DHCP that runs on the physical LXC host.

Therefore, for this and other scenarios, Orabuntu-LXC introduced a snapshot facility for rolling back the DNS-DHCP to an earlier state, for example before any containers were created on an Orabuntu-LXC VM.  Orabuntu-LXC takes an lxc-snapshot automatically of the primary LXC containerized DNS-DHCP early in it's installation steps, before the LXC containerized DNS-DHCP is touched, so that the LXC containerized DNS-DHCP can be rolled back to pre-install configuration.

A listing of an LXC snapshots of an Orabuntu-LXC containerized DNS-DHCP which is supporting LXC containers installed on the Orabuntu-LXC physical host, and a few VM's that get their IP address and DNS services from the same containerized DNS-DHCP is shown below.

The various snaps are described below.

There are two snaps (snap3, and snap4) for Ubuntu 1810B VM, because the developer wanted to retest, so the VM was restored to a pre-install snapshot, and so there are multiple snaps (3 and 4) of that VM because the Orabuntu-LXC install was run twice on that VM.  These duplicate snapshots of re-runs on a specific VM can be manually pruned back as needed.

Once, for example, the VM has been restored to the earlier pre-install snapshot, then before doing the Orabuntu-LXC install again, run the following steps.  On an Ubuntu Linux host, those steps are are shown below.

NOTE:  It is sometimes necessary to stop and start the LXC DNS DHCP container TWICE before the desired state is returned.  Use nslookup to verify that only the desired prior-state lookups are returning values.