DISCLAIMER: this is not my post is only a copy, in case the original get deleted or whatever, posting on my personal blog get easier for me to find it. You can find the original one in this link https://vpsie.com/knowledge-base/boot-single-user-mode-centos-rhel-vpsie/
The first thing to do is to open Terminal and log in to you CentOS 7 server.
After, restart your server wait for GRUB boot menu to show.
Next step is to select your Kernel version and press