Sometimes if you forgot the root password of Centos server then you may need to reset the root password.
These are some important steps to reset the root password of the server.
1: Restart the server (to restart the server you may require root password, so start directly from CPU)
2: Press Esc when server start.
3: Select 2nd option
4: Press e
Grub edit>kernel…../…LogVoloo_S (insert S)
For 6.3 just enter (space ) S or 1
6: b (inorder to boot into single user mode)
7: Check the SELinux mode
If its enforcing type
9: init 6 (reboot the system)