If for some reason you do not want to update your server kernel but want to update other packages running on CentOS, here is how you can do.
Update can be done using yum command and to exclude kernel from update we need to add exclude command.
Login to your server as root via SSH and run following command:
yum -y --exclude=kernel\* update
yum -y -x 'kernel*' update
Above command will update all packages but will leave kernel update on a CentOS server.