In order to update the cPanel software on a Linux VPS, there is 2 ways to do it.
Upgrading the cPanel software is necessary to patch some possible security breaches, and benefiting from the lastest feature.
A) How to Update cPanel through SSH.
1) Login to Your VPS or Dedicated Server in SSH with your SSH client such as Putty
2) Type your login details
3) Run the following command :
This last command is allowing you to bypass some errors you may meet during the update
B) How to Update cPanel through the GUI (User Interface)
1) Login to your WHM interface with http://youripaddress:2086
2) Type your root login details
3) Check the update settings which can be accessed from the sidebar under Home -> Server Configuration -> Update Preference
You'll have 5 kind of updates to choose from :
1 - LTS : Long Term Support which is disabling the updates and would leave you on the current version for as long as cPanel supports this very version you are currently on.
2 - STABLE : which is the widely used and tested version through a quite large public exposure.
3 - RELEASE : which is a well tested and up to date version of cPanel. There are frequent updates and it is the recommanded one to use on a production level as it is a proper balance between security - features - stability
4 - CURRENT : which is a cpanel staff's verified version which may not contain all the features, you'd have on the RELEASE level later on.
5 - EDGE : which could be assimilated to a beta to alpha version of the cPanel environment which is definitly not recommanded outside testing purposes such as a production level
4) Once you have defined, the kind of update you want and the rules about the automatic checking process, you may select in the sidebar : cPanel -> Upgrade to the latest version