On Mon, 06 Jan 2003 21:45:47 -0600
"Kevin N. Carpenter" <kevinc@seaplace.org> wrote:


> I'm working on setting up a CPU farm of diskless Gentoo based Linux 
> nodes.  I'm using DHCPD to supply each machine with a unique
> root-path, host-name, and fixed-address.
> 

Again, you can try the Adelie Linux for SSI clusters:

http://www.cerca.umontreal.ca/hpc/en/projects/adelie/index.html

which do have support.

> I've done this in the past, using a shared /usr subtree and a small 
> dedicated root subtree.  Previously, all that was needed was a unique 
> hostname and an entry in /etc/fstab referencing the root drive.
> 
> I'm trying to eliminate the need for those unique entries in the root 
> space.  This will allow me greatly simplified support of the farm,
> since Rsync could easily be used to resync all the remote root areas
> from a common build area.  Without the elimination, editing of
> /etc/hostname and /etc/fstab is required after any syncronization with
> the master image.
> 
> /etc/hostname seemed easy.  The '-H' option specified for dhcpcd in 
> /etc/conf.d/net is documented to accept the passed host-name from the 
> DHCP server.  I presumed a 'rc-update del hostname boot' would
> eliminate that script from at least complaining, and potentially from
> overriding dhcpcd's effort to create /etc/hostname.  I see that 
> /etc/runlevels/boot/modules depends on hostname - fortunetly my
> diskless 
>   kernel is compiled without modules, so I've eliminated that as well.
> 

Well, we could (or rather your :P) try to get /etc/init.d/hostname to
work with dhcpcd in setting the hostname.  I am willing to add changes
if it will work seamlessly with a non dhcpcd box ....

> Root is a differnet issue.  I can see from my logs that the diskless 
> machine mounts its proper root filesystem from the server.  After a 
> diskless boot, a mount command shows root mounted from the right 
> location, but has it mounted rsize=4096,wsize=4096,ro.  The "ro" is a 
> killer.
> 
> The only solution I've spotted (reading
> /usr/src/linux/Doc*/nfsroot.txt) is to specify a nfsroot= parameter on
> the kernel command line.  Testing with this showed initial promise, as
> demonstrated by changing the default rsize and wsize to 8192. 
> However, the read-only status remains unchange, despite specifing an
> "rw" option on the nfsroot= line.
> 

Once again, have a look at how the guys of the Adelie project does it.

> The only thing that appears to work is to specify a proper unique
> entry in /etc/fstab.  That, however, violates my design goal.
> 
> Any suggestions?
> 
> One note that spawned me to write this tomb to the -dev list is 
> something that doesn't seem quite right to me.  /etc/init.d/checkroot 
> doesn't handle an nfs root file system well.  Said script forces a
> "fsck -a /", which fails for an nfs mounted root filesystem.  I
> wouldn't be opposed to simply "rc-update del checkroot boot" to get
> around that, but 
>   checkroot does more than just check the root file system.  It also 
> mounts /proc, cleans up /etc/mtab, handles devfs, etc.  Seems to me
> that functionality should be split into a seperate script.
>

Not exactly ... It just populate /etc/mtab after / is mounted rw.  The
actual script that handles devfs, etc, are /sbin/rc ...  Once again,
I have a limited amount of pc 'resources' and do not use NFS myself.
I am however prepared to add a *tested* fix to disable checking
for a NFS rootfs.  We could get it to also mount it rw if its NFS
if you are willing to spent time ....


Regards,
 
-- 

Martin Schlemmer
Gentoo Linux Developer, Desktop/System Team Developer
Cape Town, South Africa