Background Jobs

A system like ownCloud sometimes requires tasks to be done on a regular basis without the need for user interaction or hindering ownCloud performance. For that purpose, as a system administrator, you can define background jobs (for example, database clean-ups) which are executed without any need for user interaction.

These jobs are typically referred to as cron jobs. Cron jobs are commands or shell-based scripts that are scheduled to run periodically at fixed times, dates, or intervals. cron.php is an ownCloud internal process that runs such background jobs on demand.

ownCloud plug-in applications register actions with cron.php automatically to take care of typical housekeeping operations, such as garbage collecting of temporary files or checking for newly updated files using filescan() for externally mounted file systems.


In the admin settings menu you can configure how cron-jobs should be executed. You can choose between the following options:

  • AJAX
  • Webcron
  • Cron

Cron Jobs

You can schedule cron jobs in three ways – using AJAX, Webcron, or cron. The default method is to use AJAX. However, the recommended method is to use cron. The following sections describe the differences between each method.


The AJAX scheduling method is the default option. Unfortunately, however, it is also the least reliable. Each time a user visits the ownCloud page, a single background job is executed. The advantage of this mechanism is that it does not require access to the system nor registration with a third party service. The disadvantage of this mechanism, when compared to the Webcron service, is that it requires regular visits to the page for it to be triggered.


Especially when using the Activity App or external storages, where new files are added, updated or deleted one of the two methods below should be preferred.


By registering your ownCloud cron.php script address at an external webcron service (for example, easyCron), you ensure that background jobs are executed regularly. To use this type of service, your server you must be able to access your server using the Internet. For example:

URL to call: http[s]://<domain-of-your-server>/owncloud/cron.php


Using the operating system cron feature is the preferred method for executing regular tasks. This method enables the execution of scheduled jobs without the inherent limitations the Web server might have.

To run a cron job on a *nix system, every 15 minutes, under the default Web server user (often, www-data or wwwrun), you must set up the following cron job to call the cron.php script:

# crontab -u www-data -e
*/15  *  *  *  * php -f /var/www/owncloud/cron.php

You can verify if the cron job has been added and scheduled by executing:

# crontab -u www-data -l
*/15  *  *  *  * php -f /var/www/owncloud/cron.php


You have to replace the path /var/www/owncloud/cron.php with the path to your current ownCloud installation.


On some systems it might be required to call php-cli instead of php.

Available Background Jobs

A number of existing background jobs are available to be run just for specific tasks.


These jobs are generally only needed on large instances and can be run as background jobs. If the number of users in your installation ranges between 1,000 and 3,000, or if you’re using LDAP and it becomes a bottleneck, then admins can delete several entries in the oc_jobs table and replace them with the corresponding occ command, which you can see here:

  • OCA\Files_Trashbin\BackgroundJob\ExpireTrash -> occ trashbin:expire
  • OCA\Files_Versions\BackgroundJob\ExpireVersions -> occ versions:expire
  • OCA\DAVCardDAV\SyncJob -> occ dav:sync-system-addressbook
  • OCA\Federation\SyncJob -> occ federation:sync-addressbooks

If used, these should be scheduled to run on a daily basis.

While not exhaustive, these include:


The ExpireTrash job, contained in OCA\Files_Trashbin\BackgroundJob\ExpireTrash, will remove any file in the ownCloud trash bin which is older than the specified maximum file retention time. It can be run, as follows, using the OCC command:

occ trashbin:expire


The ExpireVersions job, contained in OCA\Files_Versions\BackgroundJob\ExpireVersions, will expire versions of files which are older than the specified maximum version retention time. It can be run, as follows, using the OCC command:

occ versions:expire

SyncJob (CardDAV)

The CardDAV SyncJob, contained in OCA\DAV\CardDAV\SyncJob, syncs the local system address book, updating any existing contacts, and deleting any expired contacts. It can be run, as follows, using the OCC command:

occ dav:sync-system-addressbook

SyncJob (Federation)


It can be run, as follows, using the OCC command:

occ federation:sync-addressbooks
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