On Wed, 7 Apr 1999, Nigel Metheringham wrote:
>
> eximlist@??? said:
> > What I want to do is figure out how to configure exim so that it will
> > recognize and respect whatever method of locking sendmail is doing on
> > mailspool files, and also so that it will (in addition to whatever it
> > normally does) lock them in the same manner so sendmail will recognize
> > the locks that exim makes.
>
> The easiest answer is to do delivery the same way as sendmail does -
> which is to hand delivery off to another program (probably /bin/mail).
> You need to set up a pipe delivery into the MDA in the same way that
> sendmail does.
I've actually just found out its using procmail and am currently trying to
figure out how to tell exim to call promail the same way that sendmail
currently does. I have found one sample exim config to do this, but it
specifies "user = exim" with a comment that indicates this is correct if
procmail trusts the exim user, but no mention of what is correct if it
doesnt. I'm assuming the current sendmail setup has no notion of the exim
user ;P. I don't know how to tell what user sendmail is calling with - or
exen what user procmail expects to be called as. I figure either root or
the user associated with the delivery, favoring the latter unless procmail
needs root for some reason...
> An alternative method is to strace (truss on Solaris, other names on
> other unices) the MDA and find out how it locks the mail spool.
>
> However if you do delivery from multiple machines to an NFS mounted
> mail spool using mbox files you *will* lose mail. The only questions
> are how much and how often. NFS is not a reliable filesystem for
> mail. Things are slightly safer if you do all local delivery on one
> machine and only read on the others.
Well, there is only one machine that is the MX for the domain. But other
machines occasionally originate and deliver local mail (such as system
crontasks sending to root.. etc) to /var/spool/mail which is NFS mounted
on all machines.
> If you think that NFS semantics are up to mail then try running a Cyrus
> IMAP server over NFS - the db file structures Cyrus uses break NFS
> locking every time.
Does procmail properly lock over NFS?
I am under the impression that exim does handle locking NFS-mounted
mailspools properly - am I incorrect?
Why is locking over NFS a problem, especially if lockfiles are used? (eg
/var/spool/mail/root.lock)? Is it only a problem for flock/lockf types of
locking? (which I don't wholly understand anyway)
Better yet, is there an FAQ or some other document discussing locking
mailspools over NFS that I could refer to?
>
> Nigel.
> --
> [ Nigel Metheringham Nigel.Metheringham@??? ]
> [ Phone: +44 1423 850000 Fax +44 1423 858866 ]
>
>
>
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