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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.





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© Russell Ballestrini.