Take A Snapshot
To list a kvm vm on Linux based server [VM ID], more info
virsh list
If your KVM guests are now running with Qcow2 disk images, you can take an internal snapshot of the guest with the following command:
virsh snapshot-create [VM ID]
Alternatively, you can create a file with the following contents
<domainsnapshot>
<name>Name for the snapshot</name>
<description>Description for the snapshot</description>
</domainsnapshot>
Then pass it to the snapshotting command.
virsh snapshot-create [VM ID] [filepath]
You can take snapshots of guests whilst they are running. Whilst the snapshot is being taken, the guest will be "paused". The "state" of the guest is also saved.
List Snapshots
One can list a virtual machine's snapshots with
sudo virsh snapshot-list [VM ID]
Which will output something like:
Name Creation Time State
————————————————————
1422179589 2015-01-25 09:53:09 +0000 running
Restore Snapshot
If you want to "revert", "go to", or "restore" a previous snapshot, then execute the following command:
virsh snapshot-revert [VM ID] [Snapshot Name]
Delete Snapshot
virsh snapshot-delete [VM ID] [Snapshot Name]