Timer

Timer

About

In the src/ folder you will find some crontab configuration lines and other specific services to use with this crontab. Dockerfile contains a simple Fedora Docker Container with all the crontab parameters specified in the src folder. The Makefile script will run all this processes creating a new Docker automatically.

Using Crond

The Timer Unit executes a process in a determined time. You can easily configure this unit, using the crontab daemon. To edit the crontab configuration:

[user@docket ~]$ crontab -e

All the crontab are saved in /var/spool/cron. There's a file for every user that configured a crontab. Crontab lines are formed by: timer and command:

* * * * * /bin/command args

The five asterisk defines the following:

• Minutes (0-59)
• Hours (0-23)
• Day (1-31)
• Month (1-12)
• Week Day (0-6 (Sunday: 0))

If you let the asterisk it will mean every interval. For example an asterisk in the day parameter will mean every day. You can use the '/' to determine repetition, for example in month parameter */2, would mean every two month.

0 22 1 /3 * /bin/command args

Every three months, the first day at the 22:00 the command will be executed. Crontab also includes special aliases:

• @reboot: At the start
• @yearly: Annually
• @monthly: Once per month
• @daily/@midnight: One per day
• @hourly: Every hour

For example, with a timer for every week, like this:

[Timer]
OnCalendar=weekly

The crontab line could be:

@weekly /bin/command args