Linux KVM Virtualization Manual Low-Level Guest Export/Import Procedure: Difference between revisions
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=Overview= | =Overview= | ||
The goal of a ''snapshotting'' operation is to preserve the state of the guest | 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 [[Linux_Virtualization_Concepts#KVM_Virtual_Machine_Snapshot|snapshot a KVM virtual machine]]. It consists in taking snapshots of its XML definition and performing manual snapshots of all its storage devices. | ||
{{Error|Investigate virsh snapshot and factor it in.}} | {{Error|Investigate virsh snapshot and factor it in.}} | ||
Revision as of 19:02, 3 November 2017
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. 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