Foreword

Before backing up resources in OpenStack, it's important to understand the difference between three primary methods:

1. Intance Snapshots (Glance): These capture the entire virtual machine, including the operating system, applications, and configuration. Instance snapshots are useful for cloning VMs, creating templates, or disaster recovery scenarios. They're managed through the Glance service.
2. Volume Snapshots (Cinder): These are delta copies of the block storage volumes. Volume snapshots are not full copies and rely on the original volume for restoration, so they are mostly useful for accident recovery. They're managed through the Cinder service.
3. Volume Backups (Cinder): These are point-in-time copies of block storage volumes. Volume backups preserve the data within a volume and can be used to restore the volume to the exact state it was in when backed up. They're ideal for data recovery and are managed through the Cinder service.

Choose the appropriate method based on your recovery needs: instance snapshots for full system recovery or replication, volume snapshots for accident prevention and recovery or volume backups for full data security and recovery.

Backup VMs and volumes

Instance Snapshots

To take a snapshot of a instance for later recovery or replication, one must create an image based on the current VM.  The list of VMs/servers than can be used for the snapshot can be found with:

openstack server list

And, to create the image snapshot of a running VM with name or id <server> use the command

openstack server image create --name <image_name> <server>

where:

• --name <image_name>: the name for the new image snapshot
• <server>: the name or id of your server / VM to be backed up.

In order to see the list of images, including the recently created snapshot, one can run

openstack image list

and the specific details of the created image can be found

openstack image show <image_name>

It is recommended, though not mandatory, to shut off the server before making a snapshot of it, to make sure all the data has been flushed to disk. This can be done with the command

openstack server stop <server>

and after the snapshot it can be restarted with

openstack server start <server>

Volume Snapshots

To create a snapshot of a volume

openstack volume snapshot create [--force] --volume <volume> <snapshot_name>

with:

• --force :  create the snapshot even if the volume is attached
• –volume <volume> : the name or id of the volume to be backed up
• <snapshot_name> : the name of the new volume snapshot

To see the list of all snapshots in your cloud, or the snapshots from a specific volume, run

openstack volume snapshot list [--volume <volume>]

and to get the details of a specific snapshot

openstack volume snapshot show <snapshot_name>

It is recommended to detach the volume from the server before making a snapshot, to avoid potential crashes. This can be done with the command

openstack server remove volume <server> <volume>

and it can be reattached after the snapshot with

openstack server add volume <server> <volume>

Note that in order to make a snapshot without detaching the volume the --force  flag must be provided. The snapshot or backup of an attached volume is crash consistent.

Volume Backups

To create a backup of a volume run:

openstack volume backup create [--incremental] [--force] [--name <backup_name>] <volume>

Where:

• --incremental: create an incremental backup (requires a previous full backup)
• --force: create a backup even if the volume is attached
• --name <backup_name>: the name of the new volume backup
• <volume>: the name or id of the volume to be backed up

To list all available backups in your cloud, you can use the following command:

openstack volume backup list

Additionally, you can filter the results with additional options to list backups for a specific volume:

 openstack volume backup list --volume VOLUME_ID

It is recommended to detach the volume from the server before backing it up, to avoid potential crashes. This can be done as explained above.  One can force the backup of attached volumes with the --force  option. The snapshot or backup of an attached volume is crash consistent.

Common use cases

 These is a list of common configurations of VMs and volumes in the cloud and the recommened procedure to backing them up

Single VM

To backup a single VM, it is recommended to create an image snapshot of the instance, as shown above. It is also possible to back up the root disk of the VM as a volume, using either a snapshot or full backup, but not recommended.

Single VM and attached volume(s)

WIP

Single VM and multiple networks

WIP

Single VM and SFS

WIP

Multiple VMs

WIP

Automatic backups

WIP