What is yum-cron ? -

Environment

Red Hat Enterprise Linux Server 6.x
Red Hat Enterprise Linux Server 7.x

Issue

The yum-cron package provides a convenient way to check for, download and apply updates automatically.
The cron jobs from the yum-cron package are active immediately after installing the package and there’s no extra configuration necessary. The job will be run when daily cron jobs are set to run.

Resolution

To install yum-cron package

# yum -y install yum-cron
# chkconfig yum-cron on

Then edit /etc/sysconfig/yum-cron (RHEL 6) to set MAILTO= email address or /etc/yum/yum-cron.conf (RHEL 7) to set email_to= for email notifications.
- For RHEL 6

MAILTO=sys@example.com

For RHEL 7

email_to=sys@example.com

To exclude packages using yum-cron:-
For RHEL 6

YUM_PARAMETER=kernel* mysql*

For RHEL 7 edit below option in the base section of /etc/yum/yum-cron.conf file.

[base]
exclude=kernel* mysql*

For RHEL 7 use following option in yum-cron configuration file to install security updates.

[commands]
#  What kind of update to use:
# default                            = yum upgrade
# security                           = yum --security upgrade
# security-severity:Critical         = yum --sec-severity=Critical upgrade
# minimal                            = yum --bugfix upgrade-minimal
# minimal-security                   = yum --security upgrade-minimal
# minimal-security-severity:Critical =  --sec-severity=Critical upgrade-minimal
update_cmd = security

To start yum-cron service after editing configuration file.
For RHEL 6

# service yum-cron start

For RHEL 7

# systemctl start yum-cron