Background jobs¶
A system like Nextcloud sometimes requires tasks to be done on a regular basis without the need for user interaction or hindering Nextcloud 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 a Nextcloud internal process that runs
such background jobs on demand.
Nextcloud apps 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.
Parameters¶
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.
AJAX¶
The AJAX scheduling method is the default option. Unfortunately, however, it is also the least reliable. Each time a user visits the Nextcloud 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.
Note
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.
Webcron¶
By registering your Nextcloud 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 with your server, you must be able to
access your server using the Internet. For example:
URL to call: http[s]://<domain-of-your-server>/nextcloud/cron.php
Cron¶
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 5 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
*/5 * * * * php -f /var/www/nextcloud/cron.php
You can verify if the cron job has been added and scheduled by executing:
# crontab -u www-data -l
*/5 * * * * php -f /var/www/nextcloud/cron.php
Note
You have to replace the path /var/www/nextcloud/cron.php with the
path to your current Nextcloud installation.
Note
On some systems it might be required to call php-cli instead of php.
Note
Please refer to the crontab man page for the exact command syntax.
systemd¶
If systemd is installed on the system, a systemd timer could be an alternative to a cronjob.
This approach requires two files: nextcloudcron.service and nextcloudcron.timer. Create these two files in /etc/systemd/system/.
nextcloudcron.service should look like this:
[Unit]
Description=Nextcloud cron.php job
[Service]
User=www-data
ExecStart=/usr/bin/php -f /var/www/nextcloud/cron.php
[Install]
WantedBy=basic.target
Replace the user www-data with the user of your http server and /var/www/nextcloud/cron.php with the location of cron.php in your nextcloud directory.
nextcloudcron.timer should look like this:
[Unit]
Description=Run Nextcloud cron.php every 5 minutes
[Timer]
OnBootSec=5min
OnUnitActiveSec=5min
Unit=nextcloudcron.service
[Install]
WantedBy=timers.target
The important parts in the timer-unit are OnBootSec and OnUnitActiveSec. OnBootSec will start the timer 5 minutes after boot, otherwise you would have to start it manually after every boot. OnUnitActiveSec will set a 5 minute timer after the service-unit was last activated.
Now all that is left is to start and enable the timer by running this command:
systemctl enable --now nextcloudcron.timer
When the option --now is used with enable, the resp. unit will also be started.
Note
Selecting the option Cron in the admin menu for background jobs is not mandatory, because once cron.php is executed from the command line or cron service it will set it automatically to Cron.