Cron is a scheduling daemon, used to schedule the execution of any tasks at specified time intervals. Such tasks (cron jobs) can be schedule to run at every minute, 5 minute, hour, day of the month, day of week, etc. Generally, cron jobs are used to perform repeated tasks, such as to backup databases, clearing cache, sending emails, and more. In guide explains how to list the cron jobs.

Listing Users Cron Jobs#

The crontab files are stored on different location on different Linux distributions. Red Hat based distributions like CentOS, crontab files are stored at the /var/spool/cron directory, where on Debian based distributions files are stored in the /var/spool/cron/crontabs directory.

Run the following crontab command to get the list of all cron jobs for the currently logged in user:

crontab -l

The output show message that no crontab for USERNAME if the user has not set up any cron jobs, otherwise it will list the cron jobs.

You also can get list of the other users cron jobs by using the -u option followed by the username. For example, to list the cron jobs of the user named “kunj” you would use:

sudo crontab -u kunj -l

Each crontab file is owned by the perticular user and having the 600 permissions. Make sure you should logged in as root or sudo privileged user to view the cron jobs of other users.

To find out which users have created cron jobs, list the content of the spool directory as root or sudo user:

sudo ls -1 /var/spool/cron/crontabs

It will show output like below:

root
tecnstuff

Listing System’s Cron Jobs#

You can find the system cron jobs in /etc/crontab and the files inside the /etc/cron.d directory. Only the system administrators can be edit these crontab files.

You can view the content of crontab file using cat, less or any text editor:

cat /etc/crontab /etc/cron.d/*

In most Linux distributions you can also put scripts inside the /etc/cron. {hourly,daily,weekly,monthly} directories, and the scripts are executed every hour/day/week/month.

Make sure that all the files inside these directories must have execute permission, otherwise it will execute.

For example, to view all daily cron jobs, you would type:

ls -l /etc/cron.daily/

-rwxr-xr-x 1 root root  376 Nov 20  2017 apport
-rwxr-xr-x 1 root root 1478 Apr 20  2018 apt-compat
-rwxr-xr-x 1 root root  355 Dec 29  2017 bsdmainutils

If there is no any jobs then output will be empty.

Systemd Timers#

Systemd timers are unit files, allow you to run service units based on time. These files are end with *.timer extension.

To get list of all systemd timers on your machine run the following command:

systemctl list-timers

NEXT                         LEFT          LAST                         PASSED       UNIT                         ACTIVASun 
2020-10-04 07:09:00 UTC  41s left      Sun 2020-10-04 06:39:08 UTC  29min ago    phpsessionclean.timer        phpsesSun 
2020-10-04 08:43:55 UTC  1h 35min left Sat 2020-10-03 16:46:12 UTC  14h ago      motd-news.timer              motd-nSun 
2020-10-04 10:46:28 UTC  3h 38min left Sat 2020-10-03 20:37:04 UTC  10h ago      certbot.timer                certboSun 
2020-10-04 12:32:47 UTC  5h 24min left Sun 2020-10-04 02:39:46 UTC  4h 28min ago apt-daily.timer              apt-daSun 
2020-10-04 14:23:02 UTC  7h left       Sat 2020-10-03 14:23:linu02 UTC  16h ago      systemd-tmpfiles-clean.timer systemMon 
2020-10-05 00:00:00 UTC  16h left      Mon 2020-09-28 00:00:01 UTC  6 days ago   fstrim.timer                 fstrimMon 
2020-10-05 06:47:16 UTC  23h left      Sun 2020-10-04 06:07:18 UTC  1h 1min ago  apt-daily-upgrade.timer      apt-da

Conclusion#

This article shows you how to list the cron jobs and systemd timers on Linux system.

If you have any questions or feedback, feel free to leave a comment below.