NetBSD/gnu/dist/postfix/proto/NFS_README.html

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<title>Postfix and NFS</title>
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<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix and NFS</h1>
<hr>
<p> This question was asked on the postfix-users mailing list a
while ago: </p>
<blockquote> <p> Also, what considerations are there for file
locking or other potential problems when running Postfix with a
Netapp-style box for /var/mail delivery? I know that FreeBSD has
broken NFS file locking (both client and server?) but I'm not sure
if this is something Postfix can work around or not. </p> </blockquote>
<p> Postfix jumps several hoops in order to deal with NFS-specific
problems. Thus, Postfix on NFS is slightly less reliable than
Postfix on a local disk. That is not a problem in Postfix; the
problem is in NFS and affects other MTAs as well. </p>
<p> For queue locking within Postfix, NFS is not an issue because
you cannot share Postfix queues among multiple Postfix instances.
</p>
<p> In order to have mailbox locking over NFS, you have to configure
everything to use fcntl() locks for mailbox access (or switch to
maildir style, which needs no application-level lock controls).
</p>
<p> To turn on fcntl() mailbox locks with Postfix you specify: </p>
<blockquote>
<pre>
/etc/postfix/main.cf:
virtual_mailbox_lock = fcntl
mailbox_delivery_lock = fcntl
</pre>
</blockquote>
<p> Obviously, this approach is useful only if all other mailbox
access software also uses fcntl() locks. </p>
<p> You can also "play safe" and throw in <i>username</i>.lock files: </p>
<blockquote>
<pre>
/etc/postfix/main.cf:
virtual_mailbox_lock = fcntl, dotlock
mailbox_delivery_lock = fcntl, dotlock
</pre>
</blockquote>
<p> This is the combination that many applications end up using. </p>
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