Enable simple password for root user on CentOS

vi /etc/pam.d/system-auth as root.

Look for the following two lines:

password    requisite     pam_cracklib.so try_first_pass retry=3
password    sufficient    pam_unix.so md5 shadow nullok try_first_pass use_authtok

Comment out the first of the two lines:

#password    requisite     pam_cracklib.so try_first_pass retry=3

Remove use_authtok on the second line. Otherwise you’ll get “passwd: Authentication information cannot be recovered” error.

password    sufficient    pam_unix.so md5 shadow nullok try_first_pass

That’s it. Try changing your password again.