I have been discussing the failure mode that I have observed:

also documented in

https://bugzilla.redhat.com/show_bug.cgi?id=636628

after fsck fails during a (re)boot

Give root password for maintenance
(or type Control-D to continue):

At this stage, at every second key stroke, it reports "Login incorrect." and
repeats the above "Give root password...".

as an endless loop.

The argument has been presented on this list that it is the root user 
failure to configure a password into grub.conf or other bootloading or 
initialization applications/routines configuration or input data files.

I have been discussing this issue with a number of experienced systems 
persons, and none of us accept this argument, especially as without 
special intervention or configuration, the expected behavior was 
displayed on EL 4 and 5, as well as several other non-TUV distributions. 
  Expected behavior:  whatever root password was encoded into the 
/etc/shadow file is used by the routine that handles "Give root password 
for maintenance" is accepted, and not at every second key stroke would 
it report "Login incorrect."

When the system is first installed from physical media such as a 
bootable DVD (for EL, this is with every major release, e.g., EL 4, EL 
5, EL 6, etc.), and a root password is required to be set during 
installation, this password is put in an encrypted form in the 
appropriate file in /etc (e.g., /etc/shadow) and wherever else it might 
be required (e.g., in /boot if the particular implementation were to 
require this).  Moreover, for fsck to run during the boot process, even 
if /boot is on a separate partition from / (root partition), the fsck 
executable is on a partition that must have been mounted, and thus 
/etc/shadow should be available.  Hence, the (encrypted) password should 
be available.

The bug is that the password entry routine (as in response to the prompt 
"Give root password for maintenance") does not accept the full vector of 
characters for the root password including the Enter keystroke that 
terminates the vector.

As there are correspondents to this list that evidently feel the above 
arguments to be incorrect, references to the relevant Linux source code 
sections and design documents (e.g., state machine chart for the 
sequence that contains "Give root password for maintenance") greatly 
would be appreciated.

Yasha Karant