If you try to reinitialize the root passwd of your Linux installation through a recovering boot with init=/bin/sh, you may have the following error message :
passwd: Authentication token manipulation error
First check if your / filesystem is mounted read-write or read-only. Restart your machine and at the Grub prompt (tested on a fresh install of RHEL 6.2 with Grub version of 0.97), change ro to rw as indicated below :
kernel /vmlinuz-2.6.32-220.el6-x86_64 ro root=/dev/mapper….
kernel /vmlinuz-2.6.32-220.el6-x86_64 rw root=/dev/mapper….
An other solution is to make sure that the content of /etc/passwd and /etc/shadow are the same with the pwconv command.
As root, before reinitializing again its passwd, run the command below :
You should have no more error message.