Adding cron jobs cleanly Revision as of Sunday, 20 December 2015 at 19:56 UTC
Background
Adding jobs to /etc/cron.x keeps things modular and ‘clean’. You can add
hourly, daily, weekly and monthly (regular) scripts by creating your
script in the appropriate folder:
/etc/cron.{hourly,daily,weekly,monthly}
The cron daemon will run these hourly, daily, etc scripts at intervals
defined in /etc/crontab
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# m h dom mon dow user command
17 * * * * root cd / && run-parts --report /etc/cron.hourly
25 6 * * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6 * * 7 root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6 1 * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )
Observe the PATH variable set. This is why you don’t need to provide
explicit paths (e.g. /bin/rm), but it’s a good idea to do it anyway.
If you need to run a script akin to adding it to the crontab, you’ll
need to place it in /etc/cron.d
Adding regular scripts
Let’s say you want something to run weekly.
- Create your script
- Move it to
/etc/cron.weekly
Before you rejoice,
- You must add the
#!/bin/shline to the top of your scripts! Not
doing so will result inExec format errormessages. - You must set the permissions to 755
Adding crontab-style scripts
You’d add these to /etc/cron.d/''scriptname''. The format’s the same,
except that you must explicitly provide the user executing the script
(makes sense.) For example:
#!/bin/sh
09,39 * * * * root /bin/rm -rf /tmp/junk/*
Add that to a file, move it to /etc/cron.d. Make sure that:
- The
#!/bin/shline exists and is first. - The permissions to 755.