virt-back: restoring from backups

In a perfect world we should create backups but never need them. Although this statement holds truth, creating guest backups provides many more benefits.

The most common reasons system administrators restore from a virt-back guest backup:

• recovering from data corruption
• recovering deleted files
• recovering from a virus infection
• recovering from a compromised server
• backing out a failed change
• rolling back to a previous state
• testing disaster recovery plans
• cloning a server
• building test environments

During this article we will cover how to restore a system from a virt-back guest backup. This article will not cover how to restore a VM host server.

Virt-back guest restore procedure

In this guide our guest mbison has failed with a major corruption and we would like to restore from our backups. We have our running production guest images in /KVMROOT and our virt-back guest backups in /KVMBACK. We will be restoring the backup on the same hypervisor.

Overview:

1. Ensure the guest is shut off.
2. move the bad image file out of the way
3. untar the virt-back backup into place
4. power up the guest

Detailed Procedure:

1. Verify the guest is shut off by running:

   virt-back --info-all
   

2. We noticed that mbison was still running so we invoked:

   virt-back --shutdown mbison
   

3. Move the corrupted image file out of the way:

   mv /KVMROOT/mbison.img /KVMROOT/mbison.img.NFG
   

4. Unzip and unarchive the backup using the following command:

   sudo tar -xzvf /KVMBACK/mbison.tar.gz -C /KVMROOT --strip 1
   

5. When the untar completes, start the guest:

   virt-back --create mbison
   

6. Connect to the guest over SSH and verify that all required services and applications start. Determine if the restore was successful.

Restore guest backup on new hypervisor:

The details in this section were adapted from a tutorial given by Fabian Rodriguez.

1. Re-create any bridge network interfaces on new hypervisor (/etc/network/interfaces for Debian)
2. Adjust mbison.xml if needed (for example if you are changing paths)

sudo mkdir /KVMROOT
sudo tar -xvzf mbison.tar.gz -C /KVMROOT --strip 1
virsh create /KVMROOT/mbison.xml

Note: We use virsh create instead of virt-back create. While both commands start guest DOMs, virsh create will also register the DOM into the hypervisor.