Foreword

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

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Backup VMs and volumes

Instance Snapshots

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InstanceSnapshots InstanceSnapshots

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:

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openstack server start <server>

Volume Snapshots

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VolumeSnapshots VolumeSnapshots

To create a snapshot of a volume

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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

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VolumeBackups VolumeBackups

To create a backup of a volume run:

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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)

To backup a single VM and it's attached volumes, one must create a snapshot or backup of the instance and the volumes separately. To backup the instance, the recommendation is to create an image, as shown above. For each of the volumes attached, one can create a snapshot or a backup for each of them by following the instructions for volume snapshots or volume backups above.

Single VM and multiple networks and/or security groups

The network configuration and security groups of VMs are not recorded when performing an instance snapshot. If this information needs to be backed up in order to reconfigure the VM after restoration, we recommend storing these values in a file inside the VM. These can be done, e.g. in YAML format, with

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From these stored details, the network and security group configuration can be restored. Visit EWC - How to restore backups from VMs to find out more about how to restore instances.

Single VM and SFS

Shared File Services (SFS) cannot be backed up as they are distributed storage solutions that do not live in the same cloud. The recommended way to backup a VM with a SFS is to unmount the SFS before performing the instance snapshot, in order to avoid possible corruption, and remounting it afterwards. This can be easily done, with admin privileges, with

sudo umount <sfs_mount_point>
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<backup instance, volumes, etc>
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sudo mount <sfs_url> <sfs_mount_point>

Multiple VMs, volumes, etc

In order to backup multiple VMs, with any configuration, one can repeat the steps laid out above multiple times in succession. Attention must be when backing up volumes that are attached to multiple instances or any other possible overlapping situation. For the sake of safety, it is recommended to detach all the volumes and stop all the instances that are to be backed up.

An alternative to repeating all the steps here multiple times is to use the automation script below, where one can set up a configuration file detailing all the instances, volumes, etc, to be backed up, and run the script a single time.

Scheduling backups

It is often quite useful to schedule a backup for a specific time in the future, as well as to repeat that scheduled backup regularly, to ensure the preservation of any changes. In order to prepare a scheduled backup, with or without repetition, one can set up a cron  job that will run in the background and perform the necessary operations. A full tutorial on how to use cron is beyond the scope of this page, more details can be found elsewhere, e.g. https://crontab.guru/. Here only a few examples will be shown.

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Note: some of the syntax above is specific to bash . Add SHELL=/usr/bin/env bash to your crontab  to ensure cron runs using bash , or change the above script for its equivalent in sh .

Backup automation

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BackupAutomation BackupAutomation

The multi-step procedure for creating backups of instances and volumes, including the scheduling and repetition of backups, can been performed in a single step using the script found in the repository

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