File ownership & permission on compute nodes (Scyld)

[Donald Becker]

On Thu, 17 Jan 2002, Tony Stocker wrote:

> I'm using the 'freebie' version of Scyld [27bz-8].  We are running several 
> tests on our cluster comparing performance of our algorithms versus some 
> heavy metal platforms.  When running very I/O intensive algorithms over NFS 
> we see major performance hits, obviously.
...
> I can create the directories (as root) just fine.  But for some reason I can 
> not get the file/directory ownership to read the passwd file.  It appears to 
> read the group file fine.  What I did was copy over /etc/passwd and 
> /etc/group to the compute nodes' /etc directory.

Verify that your /etc/nsswitch.conf configuration file has both "bproc"
and "files" entries.  This file is created by /etc/beowulf/node_up
(really /usr/lib/beoboot/bin/node_up) each time a slave node is started.

> It's as if it's not bothering to look at the passwd file at all.

Correct.  For most cluster configurations there is no /etc/passwd file.
User name (really password entry -- 'pwent') information is provided by
the BeoNSS name service.  When user starts a process on a cluster slave node,
the only valid getpwent() entry for that process is that single user.

If you do add "files" to the name service switch creation in the node_up
script you might also want to 'scp -p /etc/passwd $NODE:/etc' in the
script.  

Donald Becker				becker at scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993