[gentoo-user] Using portage through NFS

[Chris Lieb]

I have read the guide on gentoo-wiki about setting up portage to work
over NFS[0] and have it mostly working.  I have two issues that I would
like to work out:

1) I use sync-eix to update portage and my overlays (via layman).  I
want the client to still be able to run sync-eix, but have it only run
`emerge --metadata` (no `emerge --sync` or `layman --sync ALL`).  What
do I need to change in the eix-sync.conf?  (Man, that's a long man page :) )

Better yet, since my overlays are all in the exported NFS filesystem
(hence, the eix database would be the same across all clients), is it
possible to export my eix cache by hardlinking it into the NFS share?
If so, how do I make the client's eix use this database instead of the
one at /var/cache/eix?

2) I use the buildpkg feature on both the server and the client since
the client can usually use the packages for its own installations
(getbinpkg).  However, sometimes I require different use flags for the
client, but I still want to keep the package locally so I can restore it
later if I need to.  I have the NFS share mounted ro to keep the client
from overwriting what is on the server, so I am guessing that portage
will throw some kind of error when it tries to save the package to disk.

I was thinking of getting around this by using some kind of union mount.
 However, I don't understand how union mounts work or if they can be
used for my situation.  What I would like is to have some directory,
lets say /var/lib/portage/packages, that I union mount on top of the
exported NFS share, at /mnt/nfs_portage/packages.  I noticed in the
Portage w/ SquashFS/aufs howto[1], they used aufs to create a rw layer
on top of a ro SquashFS.  This sounds kind of what I want, except it
appears that aufs is memory-backed instead of disk-backed.  Is this so?
 The clients are all strapped for memory, so a memory-backed fs won't be
feasible.

Does anyone have any ideas or details on how I might implement this?

Thanks,
Chris Lieb

[0] http://en.gentoo-wiki.com/wiki/Sharing_Portage_over_NFS
[1] http://en.gentoo-wiki.com/wiki/Squashed_Portage_Tree