Troubleshooting cron problems in cron.d files

Determining why a Linux cron job won't run can be maddeningly frustrating. Diagnostic information is spread across multiple logs including (depending on distribution):

/var/log/messages #look for cron specific messages
/var/log/secure #look for user authentication errors
/var/log/cron

Even after searching through the log files, problems can sometimes remain hidden.

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Background

There are two kinds of Linux crons. The first and most commonly known are user crontabs stored in

/var/spool/cron

edited and viewed with the commands:

crontab -e
crontab -l

The second cron type, file-based crons, are file scripts located in the /etc/cron.d directory in CentOS/RHEL distributions and others. We'll concentrate on the file-based variety here.

Solutions to Common Issues

Consider a cron file with the following contents:

#Run every day at 06:20 as user "username", recording stderr and stdout output to the my_script.log file
20 06 * * * username /home/username/my_script.sh > /home/username/my_script.log 2>&1

• Make sure the user in the cron file does not have an expired or locked account

chage -l [username] #is user account or pw expired?



• root user should not be expired
• File permissions for cron file should match others and be owned by root, e.g. 644
• cron file name cannot have dots; dashes and underscores are allowed
• cron file must have an ending blank line!