cron.daily, cron.hourly etc

On Ubuntu, you can put a shell script in one of these folders:

...and it will be executed daily, hourly etc.

Or, it should be executed daily, weekly, hourly etc.

A couple of gotchas:

  1. The file must have execute permission (see chmod - test -x /file/name)
  2. The file must not have a file extension. E.g. no ".sh" on the end of the file. (It's the dot that isn't allowed.)

If you add a file to /etc/cron.daily and you want to know if it will be run, try this:

run-parts --test /etc/cron.daily

...its name should be included in the output.

There is no magic to the /etc/cron.daily etc folders. You can see how they work by looking at /etc/crontab. Here's the content on a machine I know...

# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file
# and files in /etc/cron.d. These files also have username fields,
# that none of the other crontabs do.


# 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 )

It's giving something called "anacron" the room to do the needful. But if anacron is not available it uses a command called "run-parts" to cron-ify the scripts in the daily/weekly/monthly folders.

"anacron" is a tool that is usually present, and it also takes responsibility for running missed jobs, if there were missed jobs.

See also