Updating a Centos 8 server takes only a few simple command lines. Open a terminal to your server and enter the following lines waiting for each to finish before entering the next command.

Update the DNF package repository.

dnf makecache

This downloads and caches the latest metadata for any enabled repositories. This is only really necessary if the metadata is outdated.

Check for any updates.

dnf check-update

This will check to see if there are any updates available for the software installed on the server.

Update the server

dnf update or dnf upgrade

These commands will both download and install any available updates to the server. Either command can be used according to personal preference.

The server should now be fully updated and ready for you to proceed to install or set up new software. Keeping the server updated will also help keep the server as secure as possible.