On a dedicated server running CentOS, there are two common options for running system updates: manual or automatic. There are, however, less common options, such as scheduling your own auto updates with a cron job or having your system alert you whenever new updates are available.
There are a couple of reasons why you might not want automatic updates to run. One reason is that automatic updates take up valuable CPU and memory from your other applications. You may want to choose very specific times to run them. Another is that some updates could potentially break applications you have running. Executing updates manually gives you a chance to fix any potential breakage.
The first step is to edit the yum update configuration file:
# nano /etc/yum/yum-updatesd.conf
Next, edit the following variables in the file:
emit_via = email
# who to send the email to:
email_to = firstname.lastname@example.org
# who send the notifications
email_from = email@example.com
Save the file, and exit. You then must restart yum-updatesd:
# /etc/init.d/yum-updatesd restart
Email notifications will look like this:
This is the automatic update system on host.yourdomain.tld.
There are 5 package updates available. Please run the system updater.
Packages available for update:
Now, anytime your system has available updates, you will receive a notification rather than allowing the system to update the packages automatically. This will give you an opportunity to make sure the updates will go smoothly or even disable certain package updates that you do not want the system to perform.