Linux KVM Virtualization Manual Low-Level Guest Export/Import Procedure
Internal
Overview
The goal of a snapshotting operation is to preserve the state of the guest - its definition and the state of its storage - at a certain moment in time, so it can be reverted to, later, possibly after the guest was removed for a while from the virtualization host. This is the procedure to snapshot a KVM virtual machine.
This is one way to do it, and consists in manually saving the guest XML configuration and the state of the associated filesystems. The guest must be down to take the snapshot. This procedure does not produce a formal snapshot, recorded by the virtualization host. An alternative is to use
It consists in taking snapshots of its XML definition and performing manual snapshots of all its storage devices.
Investigate virsh snapshot and factor it in.
Take a Virtual Machine Snapshot
If the virtual machine has more than one storage device attached, they all must be snapshot at the same time to produce a consistent set of storage snapshots that can be reverted to.
Shutdown the Target Guest
virsh shutdown <vm-name>
Identify all Storage Devices
virsh dumpxml <vm-name>
Look for <disk> definitions. The disk definition specifies the source and the format of the virtual storage device. Example:
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/main-storage-pool/appproxy.qcow2'/>
...
</disk>
Snapshot Each Storage Device
qemu-img snapshot -c <snapshot-tag> <volume-name>
For more details about snapshot mechanics, see
qemu-img snapshot -c
Save the XML Definition
This is only necessary if we plan to modify the hardware configuration.
Restore from Snapshot
Perform the steps described in the "Take a Virtual Machine Snapshot" section in reverse order:
Restore the XML Definition
This is only necessary if the hardware configuration changed between snapshots.
Restore the Content of Storage Device from Snapshot
qemu-img snapshot -a <snapshot-tag> <volume-name>
For more details about restoration mechanics, see
qemu-img snapshot -a
Alternative
Alternative suing qemu-img create. See