Who can access the Backup module?
Only users with the global_admin or site_admin role. All other roles receive a 403 error.
The backup directory isn't writable — how do I fix it?
Create the directory and grant write access to the web server user:
mkdir -p /var/backups/omeka
chown www-data:www-data /var/backups/omeka
chmod 750 /var/backups/omeka
Then set the path in Admin > Backup > Settings.
The backup job appears to complete but no file appears in the list.
Check the job log at Admin > Jobs for error messages. Common causes: the backup directory doesn't exist or isn't writable, or there is less than 100 MB of free disk space (the module checks this before starting).
Restore aborted with "checksum mismatch".
The ZIP file on disk does not match the checksum recorded when the backup was created. The file may have been modified, partially uploaded, or corrupted in transit. Re-download or re-upload the archive and try again.
Another backup operation is already in progress.
The module uses an exclusive file lock (.backup.lock in the backup directory) to prevent concurrent runs. If the previous job crashed and left a stale lock, delete the lock file manually:
rm /path/to/backup/dir/.backup.lock
How do I exclude large media files to speed up backups?
When creating a backup, uncheck Files. The database dump and API export together are typically very small. You can back up the files/ directory separately with rsync on a different schedule.
Can I use X-Sendfile or X-Accel-Redirect for faster downloads?
The download action uses PHP's readfile() by default, which works on any server. For high-traffic sites, configure X-Sendfile (Apache) or X-Accel-Redirect (nginx) at the web server level to serve the file directly.
The API export JSON — can I use it to restore resources?
Not automatically. The export/ folder in the ZIP is a read-only snapshot for archival or migration reference. The restore action only re-imports the database and files. To re-import resources from JSON-LD, use Omeka S's built-in CSV Import or a compatible migration tool.