zobayer1/cron_job_checklist.md

## cron_job_checklist.md

      
    Raw
  

              cron_job_checklist.md
            
          
    WTF??? My cron job doesn't run?!$#%

Source: This SO Answer
Here's a checklist guide to debug not running cronjobs:


Is the Cron daemon running?

Run ps ax | grep cron and look for cron.
Debian: service cron status, if not running, service cron start or service cron restart


Is cron working?

* * * * * /bin/echo "cron works" >> /tmp/file
Syntax correct? See below.
You obviously need to have write access to the file you are redirecting the output to. A unique file name in /tmp which does not currently exist should always be writable.


Is the command working standalone?

Check if the script has an error, by doing a dry run on the CLI
When testing your command, test as the user whose crontab you are editing, which might not be your login or root


Can cron run your job?

Check /var/log/cron.log or /var/log/messages for errors.
Ubuntu: grep CRON /var/log/syslog
Redhat: /var/log/cron


Check permissions

Set executable flag on the command: chmod +x /var/www/app/cron/do-stuff.php
If you redirect the output of your command to a file, verify you have permission to write to that file/directory


Check paths

Check she-bangs / hashbangs line
Do not rely on environment variables like PATH, as their value will likely not be the same under cron as under an interactive session


Don't suppress output while debugging

Commonly used is this suppression: 30 1 * * * command > /dev/null 2>&1
Re-enable the standard output or standard error message output by removing >/dev/null 2>&1 altogether; or perhaps redirect to a file in a location where you have write access: >>cron.out 2>&1 will append standard output and standard error to cron.out in the invoking user's home directory.


Still not working? Yikes!


Raise the cron debug level

Debian

In /etc/default/cron
Set EXTRA_OPTS="-L 2"
service cron restart
tail -f /var/log/syslog to see the scripts executed


Ubuntu

In /etc/rsyslog.d/50-default.conf
Add or comment out line cron.crit /var/log/cron.log
Reload logger sudo /etc/init.d/rsyslog reload
Re-run cron
Open /var/log/cron.log and look for detailed error output


Reminder: deactivate log level, when you are done with debugging
Run cron and check log files again

Cronjob Syntax

# Minute  Hour  Day of Month      Month         Day of Week    User Command    
# (0-59) (0-23)   (1-31)    (1-12 or Jan-Dec) (0-6 or Sun-Sat)  

0       2       *             *                *          root /usr/bin/find

This syntax is only correct for the root user. Regular user crontab syntax doesn't have the User field (regular users aren't allowed to run code as any other user);
# Minute  Hour  Day of Month      Month         Day of Week    Command    
# (0-59) (0-23)   (1-31)    (1-12 or Jan-Dec) (0-6 or Sun-Sat)  

0       2       *             *                *          /usr/bin/find

Crontab Commands


crontab -l

Lists all the user's cron tasks.


crontab -e, for a specific user: crontab -e -u agentsmith

Starts edit session of your crontab file.
When you exit the editor, the modified crontab is installed automatically.


crontab -r

Removes your crontab entry from the cron spooler, but not from crontab file.


Courtesy: Jens A. Koch