Backing up your VM: Difference between revisions

Persistent VMs are designed to boot from volumes (see [[OpenStack#Booting_from_a_Volume| booting from a volume]]) thus creating a copy of the volume(s) the VM has attached to it will produce a backup. However this would not preserver things like VM flavor, public IP, and security rules. The best way to create a copy of a volume for backup purposes is to create an image from that volume. An image can be [[OpenStack#Downloading_an_Image|downloaded]] and reused to create multiple new VMs, can be [[OpenStack#Creating_a_VirtualBox_VM_from_a_Cloud_Image|accessed by VirtualBox]] on your desktop or laptop, and [[OpenStack#Uploading_an_Image|uploaded]] to other clouds.

Unfortunately, OpenStack uses the word "snapshot" to mean two different things. There are volume snapshosts, as discussed above, and snapshots of VMs. Snapshots of VMs behave in different ways depending on the flavor of your VM. If you have a persistent VM and create a snapshot of the VM, OpenStack creates a nearly empty image, which contains pointers to volume snapshots.  These pointers point to volume snapshot(s) of the persistent VM's boot volume and any attached volumes which were created as part of creating a snapshot of the VM. You can then create a new VM (boot from image (creates a new volume)) which will create new volumes from the snapshots of the volumes taken previously, boot a new VM from the root volume and attach any other duplicated volumes.

As with creating backups of persistent VMs, the main goal is to create an image of at least the root drive, and perhaps also other attached volumes if needed. However, differences with compute flavor VMs change the process of creating that image. Compute VMs are not designed to boot from volumes accessed over the network as persistent VMs are, instead they are meant to be booted from disk images which reside locally on the computer which is actually running your VM. This means there is no volume which you can click on in the OpenStack dashboard to create an image of your root disk. Instead you can do this by clicking "Create Snapshot" on your VM's drop down menu on the "Instances" tab. As with creating a snapshot with a persistent VM this creates an image; however, in this case the image isn't nearly as empty (i.e. containing only pointers to volume snapshots) since the image instead contains a copy of the VM's root drive.