Snapshot for KVM via libvirt with virsh

🔗Context

I am using KVM, and use/manage my VMs with virt-manager. But I asked myself this question: how can create or revert some snapshot?

I'm giving examples for qcow2 disk images and commands are made with virsh.

🔗Internal Disk Snapshots

You can list available VM with virsh in order to know their name:

1
2
3
4
$ virsh list
Id Name State
----------------------------------
1 vmname running

Then you can check if there already is existing shapshots for this VM:

1
2
3
$ virsh snapshot-list vmname
Name Creation Time State
------------------------------------------------------------

Next there is two possibilities to make a snapshot:

  • create a XML snapshot description file to specify the name and description of the snapshot
  • or let libvirt choose a name and no description

The XML snapshot description file must look like the following:

1
2
3
4
<domainsnapshot>
<name>vmname-snapshot1</name>
<description>description of the snapshot</description>
</domainsnapshot>

Make a snapshot with an XML file:

1
$ virsh snapshot-create vmname /path/to/description.xml

Or make a snapshot without description file:

1
$ virsh snapshot-create vmname

Note: this is much more faster to make a snapshot while the VM is stoped. But it's also possible to make a snapshot while the VM is running even if it's more slow.

If you want to see some information about the VM and snapshots you can run:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
$ qemu-img info /path/to/disk/image/vmname.qcow2
image: vmname.qcow2
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 5.2G
cluster_size: 65536
Snapshot list:
ID TAG VM SIZE DATE VM CLOCK
1 vmname-snapshot1 329M 2017-02-08 20:40:59 01:23:38.281
2 vmname-snapshot2 375M 2017-02-08 20:46:39 01:26:01.645
3 vmname-snapshot3 482M 2017-02-08 22:42:48 03:22:00.515
Format specific information:
compat: 1.1
lazy refcounts: true
refcount bits: 16
corrupt: false

To revert the VM to a snapshot, for example run:

1
$ virsh snapshot-revert vmname vmname-snapshot1

Source

Share