What if you forget root user password?
Step 2 : Scroll your cursor down till you see line starting from "linux16". Come to the end of line after "UTF-8" give a space and write "rd.break":
Step 3 : Once you come to shell prompt, remount "/sysroot" with "rw" permission i.e. read/write and then chroot to "/sysroot" directory:
# mount -o remount,rw /sysroot/
# chroot /sysroot/
Step 4 : Now we can go ahead and reset "root" user password using "passwd" command:
Step 5 : Once new root password is set and SELinux is ENABLED then create "/.autorelabel" file using touch command, so that it will relabel shadow file:
# touch /.autorelabel
This will reboot system and once it comes up, you would be able to login as root user with new password.