Crontab Examples on Linux { Centos ,Redhat, Fedora, ....etc }

Crontab Examples on Linux { Centos ,Redhat, Fedora, ....etc }

Using cron you can execute a shell-script or Linux commands at a
specific time and date. For example a sysadmin can schedule a backup
job that can run every day.

How to add a job to the cron?

# crontab –e

0 5 * * * /root/bin/backup.sh

This will execute /root/bin/backup.sh at 5 a.m every day.

Description of Cron fields

Following is the format of the crontab file.

{minute} {hour} {day-of-month} {month} {day-of-week}
{full-path-to-shell-script}

• minute:              Allowed range   0 – 59
• hour:                 Allowed range   0 – 23

• day-of-month:    Allowed range   0 – 31

• month:              Allowed range   1 – 12.    1 = January. 12 = December.

• Day-of-week:    Allowed range     0 – 7.    Sunday is either 0 or 7.

Crontab examples

1. Run at 12:01 a.m. 1 minute after midnight everyday. This is a good

time to run backup when the system is not under load.

      1 0 * * * /root/bin/backup.sh

2. Run backup every weekday (Mon – Fri) at 11:59 p.m.

      59 11 * * 1,2,3,4,5 /root/bin/backup.sh

Following will also do the same.

     59 11 * * 1-5 /root/bin/backup.sh

3. Execute the command every 5 minutes.

     */5 * * * * /root/bin/check-status.sh

4. Execute at 1:10 p.m on 1st of every month

     10 13 1 * * /root/bin/full-backup.sh

5. Execute 11 p.m on weekdays.

     0 23 * * 1-5 /root/bin/incremental-backup.sh

Crontab Options

The following are the available options with crontab:

• crontab –e : Edit the crontab file. This will create a crontab, if it

  doesn’t exist

• crontab –l : Display the crontab file.

• crontab -r : Remove the crontab file.

• crontab -ir : This will prompt user before deleting a crontab.