[Beowulf] Diskless Cluster Ram Disk Login

Peter St. John peter.st.john at gmail.com
Mon Apr 23 12:02:05 PDT 2007

I'm sure someone more hip will give you a better answer, but: long ago,
login just encrypted the password and compared it to the encrypted string in
the login file, which was pretty readable; e.g. a line might have been:
"pete", "^%&%", /home/pete, ... listing the user's login name, home
directory, and encrypted password. But that simple thing got nuked for
tighter security; now, when you login, your password gets encrypted, but
then compared to something that is less readable and stored separately
from the simple user configuration stuff. So, maybe some link to some
special file didn't get distributed to your ramdisk; e.g. if the copy
process didn't have the perms needed for the login authentication. So I'd
check for things like /etc/master.passwd on the ram disk for readability by
passwd(), but I don't know what Fedora does currently, some of these things
are flavor specific.

Also, it might be using something like Kerboros to authenticate a domain
password, but does not have access to the Kerboros server.

Maybe you could edit the login daemon (invoked in whatever serves for initab
now) to redirect standard error to a file you'd be able to read later? or
maybe pipe it into elm and get an email explaining the error while you try
and log in :-)


On 4/20/07, snj78 at comcast.net <snj78 at comcast.net> wrote:
>  Hello everyone,
> I have built a diskless cluster using FC6 x86_64 and can get a node to
> successfully boot up via dhcp and pxelinux.  I am not using a NFS because I
> want everything to reside on the node as to reduce network traffic.  Right
> now it just boots up to a text login screen and it won't accept any login or
> remote logins at all.  I have modified the rc scripts in the root file
> system many times, even copying the whole /etc directory straight over from
> the main PC, but it still won't allow any logins.  I was able to to edit the
> inittab file to 'wait' at the shell /bin/bash, but I still couldn't
> communicate with the node.  I am going to try to install SSH, make sure the
> daemon sshd is running on the node with pregenerated keys to allow logins
> without passwords, and see if that will help any.  All I want to do is be
> able to boot the node up and run an HPL benchmark on it.  What else do I
> have to do to the RAMDISK root file system to communicate wit! h the h ead
> node and allow logins via ssh, telnet, or even rsh so that I can get a
> benchmark?
> Thanks in advance for any help.
> Stephen Jenkins
> Beowulf Senior Project Group
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