[gentoo-user] Re: Using portage through NFS

[Chris Lieb]

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Chris Lieb wrote:
> 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?

I got eix working by hardlinking the cache on the server into the NFS
share and setting EIX_CACHEFILE in /etc/eixrc on the client to point to
the mounted NFS share.  All tests show that eix on both the client and
server works fine after changing this.

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

After looking into aufs a little more and trying it, I discovered that,
in it's current state in the sunrise overlay, cannot fulfill my
requirements.  The most recent version of aufs does not have support for
mounting NFS filesystems (there might be a patch out there for it, but I
don't know how to configure this in an ebuild), and the last version of
aufs that supports NFS mounts doesn't work with newer kernels.

I don't want to do UnionFS since that requires me to patch the kernel,
which is more work than I have the time for.

Since I don't see any other options for stackable filesystems, I think
I'll just set the clients to not produce binpackages and wait for
UnionFS to get into the kernel or the Gentoo patchset.

Chris Lieb
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