Document how to back up and restore Pulp 3

Author: @goosemania (ttereshc)

Redmine Issue: 6711, https://pulp.plan.io/issues/6711

Currently there are no docs about how to back up and restore a Pulp 3 installation.

• Create a page for backup and restore
• It should list all the components which needs to be backed up
• It should mention all the requirements and caveats (e.g. pulp version should be the same for backup+restore procedure, tasks in incomplete state needs to be cancelled, etc)

Details

This should be a conceptual guide. We do not want to document how to backup postgresql in great detail for example. There are so many ways to backup postgresql. Similarly for the filesystem, we can give a simple examples, but there are so many backup tools for files, e.g. cp -a rsync, or rdiff-backup, etc.

To backup

1. Stop all pulp services
2. Stop postgresql
3. Backup MEDIA_ROOT, e.g. /var/lib/pulp/
4. Backup Postgresql
5. If using S3 or Azure you'll need to archive that somehow.

Also mention that temporary files are not needed to be included in the backup

To restore

1. Stop all pulp services
2. Stop postgresql
   Restore MEDIA_ROOT (with correct file permissions)
3. Restore postgresql
4. restore S3 or Azure

Start by locating the existing Pulp 3 documentation structure and the documentation covering services, MEDIA_ROOT, PostgreSQL, and remote storage. Use the issue checklist to define the conceptual backup and restore guide, including requirements and caveats without prescribing one backup tool. Done means the guide covers the listed components, temporary files, permissions, and restore sequence.