Skill 2 in course 2.1: Users and Automation

Scheduling and Time

Run tasks once or on a schedule with at, cron and systemd timers, and keep the clock right with chrony.

Intermediate3 lessons15 exercises2 h 5 min
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You will be able to

  • Schedule a one-off job with at and manage the queue.
  • Write per-user and system cron jobs, read the five time fields without guessing, and debug a job that did not run.
  • Create a systemd service and timer pair, test a calendar expression, and list or disable timers.
  • Configure a system as a time client with chrony, check synchronisation, and set the time zone.

Lessons

  1. 01One-off and recurring jobs with at and cronRun a command later with at, and on a schedule with cron, for one user or for the whole system.atatqatrmcrontabcrontab -e/etc/cron.d0/5 exercises
  2. 02Scheduling with systemd timersPair a service with a timer, write a calendar expression, and let systemd catch up on missed runs.systemctlsystemctl list-timerssystemd-analyze calendarsystemd-runOnCalendarPersistent0/5 exercises
  3. 03Time zones and time service clients with chronySet the time zone, point the system at an NTP server with chrony, and check that it is really synchronised.timedatectlchronycchronyc sourceschronyc tracking/etc/chrony.confsystemctl restart chronyd0/5 exercises