[Gllug] A Couple of Conceptual Questions

[Nix]

On Fri, 23 Nov 2001, Dylan Brewis spake:
> This is what I want to set up:
> 
> On a network of 3 machines, each machine has a local home directory, but the 
> users need to occasionally log on to another. Is it safe to mount the local 
> home directory (which resides on its own on hda2) onto /localhome and then 
> use autofs to mount /localhome/<user> into /home/<user> along with the other 
> two from NFS? Both /localhome and /home would be mounted (or exist) in /.
> 
> What would happen if such a scheme led to recursion?

Very bad things. Don't do it that way.

Luckily there is a way to do it that is simultaneously easier to
implement, leads to identical images on all machines and avoids cycles.

Stick the actual home directories in, say,
/home/.{FQDN-of-machine-exporting-fs}; on each machine exporting some
home directories, one of those is local; the rest are NFS mounts from
the other machines.

/home on all the machines contains nothing but a bunch of symlinks
pointing into /home/.{FQDN}.

Bingo.

(Note that any such scheme means that all the machines are mounting FSen
from all the others; I have learned to my cost that this makes the
network very hard to bring up all at once. It's a good idea to use -o bg
when mounting the NFS filesystems on such a network, so that even if one
machine doesn't come up, it doesn't stall all the rest!

--- thanks to Kieran for beating me into looking into robustness... ye
gods networks can get brittle easily if you don't constantly look out
for such things...)

-- 
`Many people have tried whispering in his ear, and indeed bellowing
 with megaphones but up to now he's seemed to be completely
 clue-immune.' --- John Winters

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