If you’re using the fantastic Nextcloud and like to feel comfortable browsing all your auto-uploaded photos like once upon a time you did in some proprietary Picasa or so, you can benefit from Preview Generator, which will take care of pre-rendering the thumbnails.
As it states you must add some cron magic to get it working and the Nextcloud folks asked for a tutorial, here’s how to do it with cron or (my preference) with systemd timers.
Prerequisites
- we need to setup the job as the system user running Nextcloud (e.g.
www-data,nginx,httpd, … - depends on your distribution). You can find out by looking at the owner of the nextcloud files usingls -la - we need to use the absolut path to the
phpexecutable (which php) - we need to use the absolut path to Nextclouds
occfile, depends in which folder your Nextcloud has been installed (e.g./var/www/nextcloud/occ)
Cron
Add or create a new cronjob for the Nextcloud user:
crontab -e -u www-data
Using your favourite editor, add something like this, which will run the job at 04:00:
0 4 * * * /usr/bin/php -f /var/www/nextcloud/occ preview:pre-generate
Systemd timers
Systemd also has the possibility to run specific tasks at specific times or events. called Timers. You need to create 2 unit files:
/etc/systemd/system/nextcloud-preview-generator.service
[Unit]
Description=Nextcloud Preview Generator
[Service]
Type=oneshot
User=www-data
ExecStart=/usr/bin/php -f /var/www/nextcloud/occ preview:pre-generate
[Install]
WantedBy=basic.target
/etc/systemd/system/nextcloud-preview-generator.timer
[Unit]
Description=Run Nextcloud Preview Generator daily at 04:00
[Timer]
OnCalendar=*-*-* 4:00:00
Persistent=true
[Install]
WantedBy=timers.target
- systemd reload
systemctl daemon-reload - activate the timer
systemctl enable nextcloud-preview-generator.timer - start the timer
systemctl start nextcloud-preview-generator.timer