cron

Tips

Copy
Example of job definition:
 .---------------- minute (0 - 59)
 |  .------------- hour (0 - 23)
 |  |  .---------- day of month (1 - 31)
 |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
 |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR 
 |  |  |  |  |                  sun,mon,tue,wed,thu,fri,sat
 |  |  |  |  |
 *  *  *  *  * `user-name` `command to be executed`

Commands

Troubleshooting

• No environment variables! Use absolute paths!

• ps ax | grep cron

• start, restart, and check status of cron.service

• * * * * * /bin/echo "cron works" >> /tmp/cronTest (User syntax doesn't have the User field, root does.)

• Test script without cron.

• Check permissions for script and any redirections.

• Don't suppress output while debugging. 2>&1 to a file which you have write access instead of /dev/null. 2>&1 >> cron.out will append to user's home directory

• grep cron /var/log/syslog

• Add cron.crit /var/log/cron.log in /etc/rsyslog.d/50-default.conf and sudo /etc/init.d/rsyslog reload

Quiz

• Run quiz with the argument cron This quiz matches strings instead of evaluating commands, so input must be entered without extra whitespace in the format specified by the question.