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Take a Snapshot of the VM

A snapshot is a copy of a virtual machine's (VM) disk file at a given point in time. Snapshots provide a change log for the virtual disk and are used to restore a VM to a particular point in time.

You can take a snapshot of a VM that is online (Running state) or offline (Stopped state). When you take a snapshot of an active VM, the controller checks for the QEMU guest agent in the VM. If the guest agent is present, the controller freezes the VM file system before it takes the snapshot and unfreezes the file system afterwards. This provides for crash consistency.

info

For optimal snapshots, we recommend taking snapshots of online VMs that have the QEMU Guest Agent installed. If the guest agent is not installed, a best effort snapshot is taken.

To check whether the VM has the qemu-guest-agent active, look for AgentConnected in the Virtual Machines > Snapshots tab. The vmSnapshot Status will display if the snapshot was taken online and with or without guest agent participation.

You can take a snapshot of an online VM that has hotplugged disks. Only persistent hotplugged disks will be included in the snapshot. Only disks with a snapshot-supported storage class defined are included in snapshots. If no eligible disk is found, the Snapshot action is not possible.

Prerequisites​

  • A deployed VM.

Take a Snapshot​

  1. Log in to Palette.

  2. From the left Main Menu, click Clusters and select your cluster.

  3. Navigate to Virtual Machines > Snapshots, and click the Take snapshot button.

warning

In some situations, such as with the Fedora operating system, SELinux on the guest prevents the QEMU guest agent from quiescing the target filesystem. As a workaround, you can do one of the following:

  • Generate an appropriate local security module that permits qemu-ga to operate correctly. This is the preferred workaround.

  • Turn off SELinux Enforcing mode before the snapshot by issuing the setenforce 0 command as the root user. Enforcing can be re-enabled after the snapshot using the setenforce 1 command.

The Snapshots tab displays the vmSnapshot Status parameter with snapshot phases for the VM: InProgress, Succeeded, or Failed.

The default time for a snapshot is five minutes. If the snapshot has not successfully completed within that time, it's status will display as Failed. The VM will be unfrozen and the snapshot content will be cleaned up if necessary. The snapshot will remain in Failed state until you delete it. You can change the default snapshot time to meet your workload requirements.

warning

Snapshots should not be used as a backup method, as running a VM on a snapshot for extended periods of time can cause instability and data loss.

Validate​

  1. From the Snapshots tab, verify the vmSnapshot Status parameter displays Succeeded.

  2. If the snapshot status displays as Failed, delete the snapshot and take a new one. You may need to change the default snapshot time in the VM configuration.