Crontab never running while in /etc/cron.d

Question

Here's what I did on Debian Jessie:

• install cron via apt-get install cron
• put a backup_crontab file in /etc/cron.d/

However the task is never running.

Here are some outputs:

/# crontab -l
no crontab for root

/# cd /etc/cron.d && ls
backup_crontab

/etc/cron.d# cat backup_crontab
0,15,30,45 * * * * /backup.sh >/dev/null 2>&1

Is there something to do to activate a particular crontab, or to activate the cron "service" in itself?

Answer 1

Files in /etc/cron.d need to also list the user that the job is to be run under.

i.e.

0,15,30,45 * * * * root /backup.sh >/dev/null 2>&1

You should also ensure the permissions and owner:group are set correctly (-rw-r--r-- and owned by root:root)

Answer 2

Another thing I've observed is that the file in /etc/cron.d cannot have an extension. In my particular case, I had a symbolic link:

# my-job.crontab
* * * * * root echo "my job is running!" >> /tmp/my-job.log

$: ln -sf /home/me/my-job.crontab /etc/cron.d/
# This did not work -> job would not run

$: ln -sf /home/me/my-job.crontab /etc/cron.d/my-job
# This did work -> job ran fine

File name restriction are documented at run-part man page: http://manpages.ubuntu.com/manpages/xenial/man8/run-parts.8.html, one can pass an --regex option to override the file format.

The default cron behavior however stayed without extensions, see comments under: https://bugs.launchpad.net/ubuntu/+source/debianutils/+bug/38022

Answer 3

I think you probably just missing a necessary blank line from the end of your cron file. I had the same issue, but after checking everything listed here (user permissions, filename, cron version etc.), I realized that I did not have line break after the last entry in my /etc/cron.d/own_cron and that causes the entire file being ignored.

Answer 4

For Cron from *bian distros (like Raspbian) you need to enable the -l parameter of the Cron daemon. That is advisable to do using /etc/default/cron config file, enabling the EXTRA_OPTS.

Answer 5

If you're the only user on this computer, you might want to use just crontab -e. You'll be prompted to select an editor the first time you run the command. Then you can add this to it:

0,15,30,45 * * * * /backup.sh >/dev/null 2>&1

If you change to a normal user account, you'll need to use sudo crontab -e to configure the scripts you want scheduled to run as root.

crontab -l only displays the current crontab, once you set one up using crontab -e. If you have a cron file in /etc/cron.d/, it will not be displayed with crontab -l.

You will also need to verify that your script is executable with: chmod +x /backup.sh.

Answer 6

1. First of all, check the /var/log/syslog file for cron.d errors,

   sudo grep "cron.d" /var/log/syslog |grep -i error

   could be useful to find errors like bad usernames or bad syntax

2. If you don't have any, check for all cron.d entries into the same file with

   sudo grep "cron.d" /var/log/syslog

Answer 7

Check your version of cron.

It seems that if you are using Dillon's crond, you don't need the user in a /etc/cron.d entry.

I figured this out after nearly pulling out my remaining hair.

I have a handful of entries that have been dropped in /etc/cron.d by various installs. After some investigation, I found one of them was working. It didn't have the user. So I took the user out of the others. And they began working.