crontab Command: Tutorial & Examples
Schedule a command to be executed at a specified time
crontab command is a Linux utility that is used to schedule tasks (also known as "cron jobs") to be executed automatically at specified times. Cron is a daemon that runs in
the background on a Linux system, and it uses the
crontab command to manage a user's set of cron jobs.
crontab command can be used to create, edit, and delete cron jobs. When creating a new cron job, you specify the schedule at which the job should run, and the command that
should be executed. The schedule is specified using a series of fields, including minute (0-59), hour (0-23), day of the month (1-31), month (1-12), and day of the week (0-7, where
both 0 and 7 represent Sunday).
The syntax for creating a new cron job is typically
crontab -e this will open the crontab file in the editor specified by the
EDITOR environment variable, where you
can add new cron jobs.
For example, to schedule a job to run every day at 3:30 am, you would use the following line in the crontab file:
30 3 * * * /path/to/command
It's worth noting that the cron daemon only runs the commands under the user that created the cron job, so if you want to run a cron job as root you'll need to
sudo crontab -e and set up the job accordingly.
You can also use the
crontab -l command to list the current cron jobs and
crontab -r to remove all the cron jobs for the current user.
/etc/cron.d directory is an alternative to using the crontab command to schedule tasks on a Linux system. Instead of managing cron jobs
through individual user accounts, tasks are scheduled in the
/etc/cron.d directory. Using the
directory is simpler in some cases, as it allows multiple users to manage and schedule tasks on the system, and makes it easier to manage and troubleshoot cron jobs, also it is
more organized and centralized.
In addition to the
/etc/cron.d directory, there are also three other directories in a Linux system that are used to schedule tasks for commonly