OpenSUSE 11.0, Easy-LTSP, default prebuild image…
testsrv:~ # uname -a
Linux testsrv 2.6.25.18-0.2-default #1 SMP 2008-10-21 16:30:26 +0200 i686 i686 i386 GNU/Linux
testsrv:~ # mount -o loop,rw /srv/kiwi-ltsp/ltsp-suse-11.0.i686-0.0.1 /mnt
testsrv:~ # chroot /mnt
testsrv:/> /usr/bin/passwd
Changing password for root.
New Password:
Reenter New Password:
Cannot lock password file: already locked.
Error: Password NOT changed.
passwd: Authentication token lock busy
testsrv:/> passwd -u root
Cannot unlock the password for `root’!
testsrv:/>
Except this 
Really Great !!!