Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!giza.cis.ohio-state.edu!karl
From: karl@giza.cis.ohio-state.edu (Karl Kleinpaste)
Newsgroups: comp.unix.wizards
Subject: Re: mounting NFS filesystems directly under the root
Message-ID: <KARL.89Jun9080337@giza.cis.ohio-state.edu>
Date: 9 Jun 89 12:03:37 GMT
References: <299@wzv.uucp>
Sender: news@tut.cis.ohio-state.edu
Organization: Ohio State Computer Science
Lines: 20
In-reply-to: wietse@wzv.uucp's message of 8 Jun 89 20:17:04 GMT

wietse@wzv.uucp writes:
   In the recent past, several postings mentioned that
   >... it is not a good idea to [NFS] mount fs's directly under root
   but do not explain why that is a bad thing to do. Inquiring minds
   want to know...

The problem is due to getwd(), or whatever routine is equivalent on
your system, when a server is down.  If you have NFS filesystems
mounted directly under /, then getwd() will get stuck on the entries
for down servers, timing out at best or hanging indefinitely at worst.
The former is if you use soft mounts; the latter is the kiss of death
if you use hard mounts.

Our scheme here (borrowed in some ways from RFS concepts) is to mount
NFS filesystems under /n/servername/something, so that, e.g., if I am
in /n/dinosaur/0 when server `Flower' goes down, getwd() calls (such
as when a new csh starts up) will not get hung as getwd() traverses
directories upward, looking for the name of the directory where I am.

--Karl