Introduction
In this article, we will discuss the challenges faced when using rsync for backup jobs in TrueNAS to Debian servers and the potential cause of these issues: extended attributes (xattrs). We will cover the key concepts related to this topic, provide examples, and offer solutions to help you overcome these challenges.
What are extended attributes (xattrs)?
Extended attributes (xattrs) are metadata flags associated with files, directories, or symbolic links. They can store additional information such as access control lists (ACLs), file creation time, and other custom attributes. When backing up files with xattrs, it's important to ensure that those attributes are properly handled for a successful backup.
Challenges with using rsync for backups
By default, rsync does not preserve xattrs during the backup process. This can cause inconsistencies or issues when restoring data. Specifically, when using rsync with SSH via the root account (as in the TrueNAS case), it is crucial to handle xattrs properly.
When xattrs fail: rsync backup issues
Inconsistencies or failures during the rsync backup process can occur when:
- The source or destination system has files with xattrs.
- rsync is not configured to handle xattrs appropriately.
Preserving extended attributes with rsync
To preserve xattrs during the rsync backup process, you'll need to use the appropriate flags:
rsync -aAXv --delete-during source/ destination/
Here's what these flags do:
-a: Archive mode (preserves symlinks, permissions, timestamps, and more)-A: Preserves ACLs (Access Control Lists)-X: Preserves xattrs-v: Increases verbosity (displays more information during the transfer)--delete-during: Deletes files from the destination as soon as they are deleted from the source
Using rsync over SSH for remote backups
To run your rsync backup over SSH as a root user, the command will look like:
rsync -aAXv --delete-during --rsh=ssh root@remote_server:/path/source /path/destination
Preserving xattrs during the rsync backup process can be a challenge, especially when handling remote backups over SSH. By utilizing the correct flags, you can ensure proper handling of these attributes and create consistent, reliable backups. Remember, using the -aAXv flags and the --delete-during option can help you achieve a successful backup process with rsync.