[gentoo-dev] Diskless Gentoo ndoes

["Kevin N. Carpenter" <kevinc@seaplace.org>]

Hello.

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.

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.

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.

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.

Thanks for your attention.

Kevin C.


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