[jcalvinowens]

If it's Linux, you can bind-mount the rootfs read-only and chroot into it:

    mahler ~ # mkdir /roroot
    mahler ~ # mount -o bind,ro / /roroot
    mahler ~ # chroot /roroot
    mahler / # passwd
    Enter new password: 
    Re-type new password: 
    passwd: Authentication token lock busy
    passwd: password unchanged

[dmd]

Oh, that's a good idea.