UCS 2.4 - Univention

10 Basic System Services
first hard drive. The Grub root partition can be represented in this notation by the Univention Configuration
Registry variable grub/groot.
The root partition which is handed over to the booting kernel, is independent from the above notation. It
can be changed via the Univention Configuration Registry variable grub/root, and has to be declared in
standard Linux partitions syntax.
10.9 Executing recurring actions with Cron
Regularly recurring actions (e.g., the processing of log files) can be started at a defined time with the Cron
service. Such an action is known as a cron job.
10.9.1 Hourly/daily/weekly/monthly execution of scripts
Four directories are predefined on every UCS system, /etc/cron.hourly/, /etc/cron.daily/,
/etc/cron.weekly/ and /etc/cron.monthly/. Shell scripts which are placed in these directories
and marked as executable are run automatically every hour, day, week or month.
10.9.2 Defining local cron jobs in /etc/cron.d
A cron job is defined in a line, which is composed of a total of seven columns:
• Minute (0-59)
• Hour (0-23)
• Day (1-31)
• Month (1-12)
• Weekday (0-7) (0 and 7 both stand for Sunday)
• Name of user executing the job (e.g., root)
• The command to be run
The time specifications can be set in different ways. One can specify a specific minute/hour/etc. or run
an action every minute/hour/etc. with an *. Intervals can also be defined, for example */2 as a minute
specification runs an action every two minutes.
Some examples:
30 * * * * root /usr/sbin/jitter 600 /usr/share/univention-samba/slave-sync
*/5 * * * * www-data /usr/bin/php -q /usr/share/horde3/kronolith/scripts/reminders.php
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