Cron job every 6 hours

To run a cron job every 6 hours, use 0 */6 * * *. Every 6 hours, on the hour.

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Sunday11 Oct 2026, 00:00
Sunday11 Oct 2026, 06:00
Sunday11 Oct 2026, 12:00
Sunday11 Oct 2026, 18:00
Monday12 Oct 2026, 00:00

Crontab Line

0 */6 * * * /path/to/job.sh >> /var/log/cron-job.log 2>&1

Cron Expression Generator

0 */6 * * * explained

Expression0 */6 * * *
MeaningEvery 6 hours, on the hour
Runs per Week28
Crontab Line0 */6 * * * /path/to/job.sh
systemd OnCalendar00/6:00
Time ZoneThe server's, unless CRON_TZ is set

Steps like */6 line up with the clock, not with the moment you saved the crontab: */15 runs at :00, :15, :30 and :45 every hour. Cron has no way to say "15 minutes after the last run".

If a run can take longer than the gap between runs, stop runs overlapping with flock: 0 */6 * * * flock -n /tmp/job.lock /path/to/job.sh. A second copy then exits straight away instead of piling up.

Cron runs jobs with a minimal environment: use full paths, and send output to a log file (>> /var/log/job.log 2>&1) so errors are not lost.

Other Schedules

Every Minute · * * * * *Every 2 Minutes · */2 * * * *Every 5 Minutes · */5 * * * *Every 10 Minutes · */10 * * * *Every 15 Minutes · */15 * * * *Every 30 Minutes · */30 * * * *Every Hour · 0 * * * *Every 2 Hours · 0 */2 * * *Every 6 Hours · 0 */6 * * *Every 12 Hours · 0 */12 * * *Every Day at Midnight · 0 0 * * *Every Day at 2am · 0 2 * * *Every Day at Noon · 0 12 * * *Twice a Day · 0 0,12 * * *Every Weekday at 9am · 0 9 * * 1-5Every Weekend Day at 10am · 0 10 * * 6,0Every Monday · 0 0 * * 1Every Sunday · 0 0 * * 0First Day of Every Month · 0 0 1 * *The 15th of Every Month · 0 0 15 * *Every Quarter · 0 0 1 1,4,7,10 *Once a Year · 0 0 1 1 *

Questions

How do I run a cron job every 6 hours?
Run crontab -e and add: 0 */6 * * * /path/to/job.sh
How do I check the cron job ran?
Look in the job's own log if it writes one, or the system log: grep CRON /var/log/syslog on Debian and Ubuntu, or journalctl -u cron (cron.service is crond on RHEL).
What is the systemd timer equivalent of 0 */6 * * *?
OnCalendar=00/6:00 in a .timer unit. systemd timers can also catch up on missed runs with Persistent=true.

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