Moodle Course Backup Temporary Storage Limits

Answer

The Moodle backup process writes all temporary files – the staging area before the final .mbz is produced – to the directory defined by $CFG->tempdir. By default this is moodledata/temp, but the location is fully configurable. There is no built‑in Moodle setting that caps the size of these temporary files; the only limits are the free space on the file system hosting $CFG->tempdir and the general PHP limits (memory_limit, max_execution_time, etc.).

Redirecting the Temporary Directory

1. Choose a mount point. Create or select a partition with sufficient space, e.g. /mnt/backuptmp. Ensure the web‑server user (often www-data or apache) can read and write there.
2. Update Moodle’s configuration.
   • Via config.php:

     $CFG->tempdir = '/mnt/backuptmp';

   • Or through the UI: Site administration → Server → System paths → Temporary directory – enter the absolute path and save.
3. Verify the change. In the admin UI, the Temporary directory field should now show the new path.
4. Test a backup. While a backup is running, list the temporary directory:

   ls -lh /mnt/backuptmp

   You should see files with names like temp_*.tmp or backup_*.zip.
5. After completion, confirm that the final .mbz is placed in the usual moodledata/backup location and that the temporary directory’s usage has returned to baseline.

Controlling Temporary File Size

Moodle does not expose a per‑backup size limit. The only practical controls are:

• Ensure the partition hosting $CFG->tempdir has enough free space for the largest expected backup.
• Implement external monitoring or disk‑quota enforcement on that partition.
• Adjust PHP limits if the backup process is being throttled by memory or execution time.

Additional Considerations

• Changing $CFG->tempdir affects all Moodle temporary operations – caches, file uploads, session handling – so the new location must be reliable and not mounted with restrictive options like noexec.
• On shared hosting, you may lack permission to modify $CFG->tempdir or to create a new mount point; contact your provider first.
• Regularly monitor free space on the temporary partition to avoid silent backup failures.

Summary

Redirect the backup temp directory by setting $CFG->tempdir to a path on a separate partition, either in config.php or via the admin UI. Moodle provides no configurable limit for temporary backup file size; you must rely on the underlying file system’s free space and external monitoring.