How to Check Cron Logs on Ubuntu 18.04

In this article, we'll look at how to check cron logs and monitor jobs in real time in Ubuntu 18.04. A cron job is a task scheduler used for automation of repetitive tasks in a Linux environment. It is normally executed at a specific time and date as dictated by the system administrator. Cron logs really help admin to verify if the cron jobs have run or not at the particular time.

Usually, you can view cron events using

cat /var/log/syslog | grep cron

Output

However, it's more preferable to have a separate cron.log file which you can use to monitor cron events.

Setting up cron.log file

First off go to /etc/rsyslog.d/50-default.conf file and search for this line #cron.* /var/log/cron.log

 cat /etc/rsyslog.d/50-default.conf | grep cron

Output

#cron.*                         /var/log/cron.log
#       cron,daemon.none;\

Using your favorite text editor, open the file and uncomment the line as shown in line 10

Next, create cron.log file

vi /var/log/cron.log

Restart the rsyslog service

systemctl restart rsyslog

Check the status of rsyslog to ensure it is running

systemctl status rsyslog

Sample Output

From then henceforth all log will be saved at /var/log/cron.log file.

Next, we are going to create a watchcron command which we will invoke to have a glimpse at the cron events in real time.

create the watchcron file

nano watchcron

Add the following

#!/bin/bash
watch -n 10 tail -n 25 /var/log/cron.log

Save and exit

Note :

watch -n 10 refreshes the page every 10 seconds.

tail -n 25 displays the last 25 entries.

Give the watchcron file execute permissions

chmod +x watchcron

Copy it to /usr/sbin as shown

cp watchcron /usr/sbin

To watch real-time cron events run

 watchcron

Sample Output

Every 10.0s: tail -n 25 /var/log/cron.log               Sun May 13 14:00:19 2018

May 13 06:47:01 ip-172-31-41-251 CRON[26305]: (root) CMD (test -x /usr/sbin/anac
ron || ( cd / && run-parts --report /etc/cron.weekly ))
May 13 07:17:01 ip-172-31-41-251 CRON[26993]: (root) CMD (   cd / && run-parts -
-report /etc/cron.hourly)
May 13 08:17:01 ip-172-31-41-251 CRON[28255]: (root) CMD (   cd / && run-parts -
-report /etc/cron.hourly)
May 13 09:17:01 ip-172-31-41-251 CRON[29487]: (root) CMD (   cd / && run-parts -
-report /etc/cron.hourly)
May 13 10:11:01 ip-172-31-41-251 CRON[30655]: (root) CMD (/sbin/reboot)
May 13 10:11:34 ip-172-31-41-251 cron[1226]: (CRON) INFO (pidfile fd = 3)
May 13 10:11:34 ip-172-31-41-251 cron[1226]: (CRON) INFO (Running @reboot jobs)
May 13 10:17:01 ip-172-31-41-251 CRON[2506]: (root) CMD (   cd / && run-parts --
report /etc/cron.hourly)
May 13 11:17:01 ip-172-31-41-251 CRON[2986]: (root) CMD (   cd / && run-parts --
report /etc/cron.hourly)
May 13 12:17:01 ip-172-31-41-251 CRON[3252]: (root) CMD (   cd / && run-parts --
report /etc/cron.hourly)
May 13 13:17:01 ip-172-31-41-251 CRON[3513]: (root) CMD (   cd / && run-parts --
report /etc/cron.hourly)

If you don't wish to receive emails from cron, append this line at the beginning of your crontab file

MAILTO=""

In this article, we have shown you how to monitor cron jobs logs in real time using a single command. Feel free to try out the procedure and give us your feedback. Thank you.