Hi,
I ve forgotten my root passwd on centos 6,

I tried to change it as I used in debian (in debian it works perfectly) , that is:

use a cd live (or installation cd1), to access the hd,
I mount my root partition and mount proc and devices

I tried the command passwd, no error reprorted, but after reboot the passwd had´t changed.
then I decided to remove passwd from /etc/shadow (delete the
second field).

OK, now I can access my machine without passwd, BUT I CAN´T GIVE ANY PASSWORD!!!! I RECEIVE THIS ERROR

# passwd
Changing password for user root.
New password:
Retype new password:
passwd: Authentication token manipulation error

any idea to fix the problem.
thanks a lot

Hi,

The easy way is to boot into single user mode. In the boot screen you have a couple of seconds to type any key to enter into the grub menu. Choose the line you want to edit (most likely the first) and type 'e' (without the quotes). Next select your kernel boot line and type 'e' again. On that line at the end add the word 'single' (again without quotes), type <enter> and next 'b' to boot. You'll be logged in on a single user mode and will be able to run passwd to reset the root passwords. After that change run level or reboot.

That's the normal, fastest and easiest way on CentOS that I know of. But... Most likely your /etc/shadow has been corrupted so you might want to have a look at:
to try and save the day if the first option doesn't work for you.

Kind regards,

Eric