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I'm using Ubuntu 14.04, and the cron daemon is running:

# ps ax | grep cron
822 ?        Ss     0:00 cron

but it is not executing any jobs. I was previously getting entries in /var/log/syslog such as this:

2014-05-04T11:47:01.839754+01:00 localhost CRON[29253]: (root) CMD (test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly ))

but now there are no cron-related entries. I was also getting entries like this in /var/log/auth.log:

2014-05-04T11:47:01.839183+01:00 localhost CRON[29252]: pam_unix(cron:session): session opened for user root by (uid=0)
2014-05-04T11:47:13.495691+01:00 localhost CRON[29252]: pam_unix(cron:session): session closed for user root

but again, now there are no cron-related entries.

I am not aware that anything has changed. I have tried restarting cron:

# service cron restart
cron stop/waiting
cron start/running, process 24907

I tried using crontab -e to add a cron job * * * * * date >> /tmp/somefile which worked, but it installed a new crontab in /var/spool/cron/crontabs/root, whereas I want cron to use the file in /etc/crontab.

Is there any debug option I can use, or a log somewhere that might give an error message that I can investigate?

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  • 1
    What displayed to crontab -l? Commented May 8, 2014 at 20:05
  • no crontab for root. Commented May 8, 2014 at 20:12
  • I believe if you do just a little bit of searching on this SE site you'll have an answer. This is a fairly common problem. Commented May 9, 2014 at 1:11
  • Crons retrieved using the crontab command (-l switch) are user-dependent, while /etc/crontab is used to store system-wide crons. For this reason, tasks saved in /etc/crontab will not appear in anyone's crontab -l. Commented Aug 18, 2014 at 11:15
  • Note that Server Fault has a canonical question about cronjob debugging that may help. Commented Nov 8, 2017 at 22:36

4 Answers 4

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To further help you debug what is wrong with your cron jobs, you should check your mail. This is usually stored in a file like /var/mail/<user_name> or /var/spool/mail/<user_name>.

These two files are actually hardlinks on my Debian box, but I don't know if this is standard.

Explanation

From the cron(8) page:

When executing commands, any output is mailed to the owner of the crontab (or to the user named in the MAILTO environment variable in the crontab, if such exists).

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  • I have checked mail; none is being generated, nor is there a dead.letter file. Commented May 9, 2014 at 5:59
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You have shown that there is no crontab for root, do any users have a crontab entry? If you are only using root then you could also check the following directories: /etc/cron.daily/ - /etc/cron.hourly/ - /etc/cron.monthly/ - /etc/cron.weekly

on my machine (centos 6.4) i have mlocate.cron inside of the /etc/cron.daily/ directory and cron runs that script daily.

so I think you just need to add cron jobs.

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  • But there is a crontab file in /etc/crontab. Maybe the question is why does crontab -l not acknowledge it? Commented May 9, 2014 at 5:59
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I resolved this by changing the permissions on /etc/crontab to the following:

-rw-r--r-- 1 root root 778 May 10 21:31 /etc/crontab

Previously it was -rw-rw-r--. That was the only change. It wasn't working, now it is. Still not sure why.

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    The root crontab would execute any commands as root. Permissions allowing write access to non-root would be considered a security hole. Commented May 16, 2014 at 23:10
  • @ChuckCottrill: But the group write bit would only have given write access to those in the root group - which is presumably just root user(s)? Commented May 17, 2014 at 19:24
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I also had a similar type of problem, but after specifying the root as user on the /etc/crontab, the cron job started triggering.

It might be due to the syntax followed on the crontab -e which is different from the /etc/crontab.

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