cron

Warning

If a cron script in /etc/cron.d has a . in the file name, then it will not run! ref configs with dots in file name not working in /etc/cron.d

Links

Configuration (System)

/etc/crontab

email

To email the output of your cron job to a specific user, add the following at the top of your cron script:

MAILTO=patrick@mycompany.com

To stop emails:

MAILTO=

…or pipe the output of your command to a file (see Logging below)…

Logging

To write output to a log file, add the following after your command:

>> /home/my-user-name/logs/update_index.log 2>&1

Note: This re-directs stdout AND stderr which isn’t much good if you are doing a SQL dump to stdout. In this case, try something like this:

mysqldump --host=localhost --user=patrick --password=mypassword redmine > $DUMP_FILE 2>> $LOG_FILE

System

System cron tasks are configured from the /etc/crontab file. The /etc/crontab file is set-up to run commands hourly, daily, monthly and weekly:

/etc/crontab

To set-up a task to run at these times, just add your shell script to the relevant folder:

/etc/cron.daily
/etc/cron.hourly
/etc/cron.monthly
/etc/cron.weekly

Note

Check your shell script file name does NOT have an extension. For details, see run-parts doesn’t run script with sh extension

Note

To run a command at a different time, setup your file in the /etc/cron.d folder. Note: The files in this folder are in crontab format with the user inserted before the command (see Sample, System below):

User

Tip

It is probably less confusing to use the global cron system for jobs on a server. It Will be easier to work out which processes are being run…

To view your own crontab file:

crontab -l

To edit your own crontab file:

crontab -e

To edit the crontab file of another user:

crontab -e -u username

Sample

System

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=me@mail.com
HOME=/home/patrick/

# minute  (0-59),
# |       hour (0-23),
# |       |       day of the month (1-31),
# |       |       |       month of the year (1-12),
# |       |       |       |       day of the week (0-6 with 0=Sunday).
# |       |       |       |       |       user        commands
  0       0       *       *       *       myusername  /usr/bin/python2.4 /home/USERNAME/scripts/svn-hot-backup.py --archive-type=zip --num-backups=10 /home/USERNAME/svn/REPOSITORY_NAME/ /home/USERNAME/backup/svn/

User

A nice looking cron script layout (from the link below):

MAILTO=me@mail.com
# minute (0-59),
# |       hour (0-23),
# |       |       day of the month (1-31),
# |       |       |       month of the year (1-12),
# |       |       |       |       day of the week (0-6 with 0=Sunday).
# |       |       |       |       |       commands
  0       0       *       *       *       /usr/bin/python2.4 /home/USERNAME/scripts/svn-hot-backup.py --archive-type=zip --num-backups=10 /home/USERNAME/svn/REPOSITORY_NAME/ /home/USERNAME/backup/svn/

Backing up your Subversion (SVN) repository on Dreamhost with cron

Note

This sample does not include the user parameter. The user parameter is required for scripts in cron.d.

Working Hours

Cron Job every weekday during working hours. This example checks the status of the database every weekday (i.e. excluding Sat and Sun) during the working hours 9 a.m – 6 p.m:

00 09-18 * * 1-5 /home/ramesh/bin/check-db-status

00     0th Minute (Top of the hour)
09-18  9am, 10am, 11am, 12am, 1pm, 2pm, 3pm, 4pm, 5pm, 6pm
*      Every day
*      Every month
1-5    Mon, Tue, Wed, Thu and Fri (Every Weekday).