nixCraft published a tutorial about how to check CentOS/RHEL needs a full reboot.
How to check if CentOS / RHEL needs a full reboot
Explains how to check if CentOS / RHEL (Red Hat Enterprise Linux) needs a full reboot and which services need to be restarted from the CLI.
How to check if CentOS / RHEL needs a full reboot - nixCraft