Page 80 - RHEL8 BOOK

Job Scheduling using crontab
we can schedule and run tasks in the background automatically at regular intervals using
Crontab command. Crontab executes jobs automatically in backend on specified time interval.

Running the Crond Service:
Step 1: To run the crond service in the current session, type the following command as root:
[root@sun ~]# systemctl start crond

Step 2: To configure the service to be automatically started at boot time, use the following command:
[root@sun ~]# systemctl enable crond

Step 3: To stop the crond service, run the following command as root:
[root@sun ~]# systemctl stop crond

Step 4: To check the status of crond service, run the following command as root:
[root@sun ~]# systemctl status crond

Configuring cron jobs:
Step 5: The configuration file for cron jobs is the /etc/crontab. The file contains the following:
[root@sun ~]# vi /etc/crontab

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
HOME=/
# For details see man 4 crontabs
# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * username command to be executed
15 11 * * * root reboot

Step 6: To add or edit job in crontab, use following command:
[root@sun ~]# crontab –e

Step 7: To edit other users crontab use command as below:
[root@sun ~]# crontab -u username -e
[root@sun ~]# crontab -u mohit –e

List Scheduled Cron Jobs:
Step 8: To view cron jobs of current user use following command:.
[root@sun ~]# crontab –l

Step 9: To view cron jobs of other user use following command:
[root@sun ~]# crontab -u username –l

S. Pradhan
(MCA, MBA-IT, BCA, CCNA, MCSA 2012, RHCE, ETHICAL HACKING)
Email Id:-spradhan.iiht@gmail.com
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