http://wiki.docking.org/index.php?action=history&feed=atom&title=CronCron - Revision history2026-04-07T06:04:09ZRevision history for this page on the wikiMediaWiki 1.39.1http://wiki.docking.org/index.php?title=Cron&diff=9459&oldid=prevBenrwong: Created page based on "ALL ABOUT CRON" from lab manual2016-06-30T17:55:14Z<p>Created page based on "ALL ABOUT CRON" from lab manual</p>
<p><b>New page</b></p><div> vim /etc/crontab<br />
In this file you should see this:<br />
SHELL=/bin/bash<br />
PATH=/sbin:/bin:/usr/sbin:/usr/bin<br />
MAILTO=root<br />
HOME=/ <br /><br />
# For details see man 4 crontabs <br /><br />
# Example of job definition:<br />
# .---------------- minute (0 - 59)<br />
# | .------------- hour (0 - 23)<br />
# | | .---------- day of month (1 - 31)<br />
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...<br />
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat<br />
# | | | | |<br />
# * * * * * user-name command to be executed<br />
<br />
In /etc, there are five directories associated with cron:<br />
cron.d, cron.daily, cron.hourly, cron.monthly and cron.weekly<br />
<br />
To enable the scripts in these directories to be run you need to add them to the crontab, so, /etc/crontab should look like this:<br />
<br />
SHELL=/bin/bash<br />
PATH=/sbin:/bin:/usr/sbin:/usr/bin<br />
MAILTO=root<br />
HOME=/ <br /><br />
# For details see man 4 crontabs <br /><br />
# Example of job definition:<br />
# .---------------- minute (0 - 59)<br />
# | .------------- hour (0 - 23)<br />
# | | .---------- day of month (1 - 31)<br />
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...<br />
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat<br />
# | | | | |<br />
# * * * * * user-name command to be executed<br />
01 * * * * root run-parts /etc/cron.hourly<br />
02 4 * * * root run-parts /etc/cron.daily<br />
22 4 * * 0 root run-parts /etc/cron.weekly<br />
42 4 1 * * root run-parts /etc/cron.monthly <br /><br />
What this means is that:<br />
cron.hourly will run every hour on the first minute.<br />
cron.daily will run at 4:02 am everyday<br />
cron.weekly will run every week at 4:22 am on Sunday<br />
cron.monthly will run on the first of every month at 4:42 am <br />
I added a script to clean out the /tmp directory every night like this: <br />
In /etc/cron.daily/ I created a file called clean_tmp. I added the lines:<br />
<br />
#!/bin/bash <br /><br />
rm -rf /tmp/*<br />
<br />
Saved and quit. Then I typed chmod a+x clean_tmp<br />
That’s it!<br />
<br />
[[Category:Sysadmin]]</div>Benrwong