Subject: NFS/Locking?

From: Alex Tang <[email-masked]>
Date: Sat, 29 Jan 1994 18:02:35 -0500 (EST)

Hi.  this has probably been discussed before, but I was wondering how
user-contention locking works when the user's spool directory is
NFS-mounted.  Particularly, I have my spool directory NFS mounted to a
bunch of different machines.  Normally, If I open two pine sessions from
the same machine, the first session gets the lock taken away, and the
INBOX becomres Read Only.  I just noticed that if I start pine from
machine a, and while it is open, start a pine session from machine b (that
has the same spool dir), they both have Read/Write access to the inbox.
Am I doing something wrong?

Thanx. 
...alex...
Alex Tang  ---  [email-masked][email-masked]
-----------+    U of M, SNRE: Student and Computer Consultant II,
PGP on req.|    ITD/CSS Consultant, Short asian with long hair :)
                WWW -> http://www.css.itd.umich.edu/users/altitude/

---

From: Mark Crispin <[email-masked]>
Date: Sat, 29 Jan 1994 16:01:52 -0800 (PST)

> Am I doing something wrong?

Yes, you are doing something wrong, regrettably.  You are using NFS for 
remote mail access instead of IMAP.

We understand that NFS access of mail is popular at many sites, and we go 
to great lengths to try to make it work.  However, there are technical 
limitations which severely restrict our ability to do so.  We believe 
that Pine works as well over NFS as other UNIX mail tools; unfortunately, 
we are (at least for the time being) unable to make NFS access via Pine 
work at the same high standard we have for local access.

Pine's locking against multiple simultaneous read/write sessions only 
works with local files.  It does not work over NFS.  At best, Pine is 
reduced to the same level of interlocking as ordinary UNIX mail utilities 
have; however, note that in certain circumstances that translates into 
*no* locking at all.

Pine does try pretty hard to detect the situation in which locking has 
failed and another mailer has stepped on Pine.  Unless Pine is absolutely 
sure what it is doing is safe, it will decline to write to the mail file.