How can I run command every six hours every day?

Use 0 */6 * * *: four runs a day at 00:00, 06:00, 12:00 and 18:00, anchored at midnight. To shift the phase use a range, e.g. 0 3-23/6 * * * for 03/09/15/21.

I am trying to add a crontab entry to execute a script every 30 minutes, on the hour and 30 minutes past the hour or something similar. How can I do this?

Use 0,30 * * * * to run on the hour and at half past (48 runs a day), or 30 * * * * for half past only (24 runs). Cron matches clock minutes, not elapsed time.

How can I set up a cron job to run every night at 2:30? I am familiar with configuring it to run at 2:00, but not 2:30.

Use 30 2 * * *: minute comes before hour in cron, so 2:30 AM is 30 2, not 2 30. For 2:30 PM use 30 14. The run happens in the scheduler's timezone.

How can I write a Crontab that will run my script every 2… - Cron answer & example

Q: How can I write a Crontab that will run my script every 2 hours?

Use 0 */2 * * *: it runs at the top of every even hour (00:00, 02:00 … 22:00). For odd hours use 0 1-23/2 * * *. Cron matches clock times, not intervals.

Question

How can I write a Crontab that will run my script every 2 hours?

Answer

Use 0 */2 * * * to run your script at the top of every even-numbered hour: 00:00, 02:00, 04:00, and so on through 22:00. Add the script path after the expression in your crontab. This is a clock-based schedule, not a two-hour countdown measured from installation time or from the previous run.

crontab

# at the top of every second hour
0 */2 * * *

crontab

# the complete crontab line
0 */2 * * * /home/username/script.sh

Read the five fields as minute, hour, day of month, month, and day of week. The minute field 0 fixes each run at minute zero. The hour field */2 starts at the hour field's minimum value, 0, and selects every second hour, so it matches 0, 2, 4, 6, and the remaining even hours through 22. The three trailing wildcards match every day of the month, every month, and every day of the week. If you want the same two-hour spacing on odd-numbered hours instead, use 0 1-23/2 * * *, which runs at 01:00, 03:00, and so on through 23:00.

Run 0 */2 * * * on Crontap

Why this matters

The expression anchors runs to even clock hours. It does not remember when the script last ran, wait two hours after completion, or automatically make up a run missed while the machine was unavailable. Confusing schedule semantics with interval semantics can create a longer gap than expected after downtime. It can also cause simultaneous load spikes when many machines share the same expression and all start work at 00:00, 02:00, and the other matching hours.

Read the dedicated guide: Cron every 2 hours.

Cron schedule used

What it does

0 */2 * * *

At 0 minutes past the hour, every 2 hours, every day.

Run in Crontap Cheatsheet

Calendar

View future cron matches in a calendar

September 2026 · UTC

0 runs

See this cron expression on the calendar view example

What it does

Calendar

Related questions

How can I write a Crontab that will run my script every 2 hours?

How can I run command every six hours every day?

I am trying to add a crontab entry to execute a script every 30 minutes, on the hour and 30 minutes past the hour or something similar. How can I do this?

How can I set up a cron job to run every night at 2:30? I am familiar with configuring it to run at 2:00, but not 2:30.

Related cron questions

How can I run command every six hours every day?

I am trying to add a crontab entry to execute a script every 30 minutes, on the hour and 30 minutes past the hour or something similar. How can I do this?

How can I set up a cron job to run every night at 2:30? I am familiar with configuring it to run at 2:00, but not 2:30.

How do you run a cron job every minute only on specific hours?

Point Crontap at any URL. Pick any cron. Done.