Hi.
I know, this is a pretty old thread, but since I just ran into similar problems while setting up my one-user-per-virtual-domain postfix + multi-instance-dovecot/-lda, I thought I might share my "fix" in this related (and most useful) thread.
My setup might not be used often - I am running two dovecot instances (on different IP addresses on the same server, in case you're wondering), with the first instance exporting the auth-master socket. I am using different UID/GIDs for my virtual domains/mailboxes. I couldn't get postfix setgid accordingly when callig deliver, and I didn't want to use SUID on deliver. The versions I am using are:
dovecot 1.0.13 postfix 2.3.8
My first dovecot instance is using:
auth default { socket listen { master { path = /var/run/dovecot/auth-master mode = 0600 user = vmail } } }
The other is using:
protocol lda { auth_socket_path = /var/run/dovecot/auth-master }
And my postfix's master.cf is:
dovecot unix - n n - - pipe flags=DRhu user=vmail:vmail argv=/usr/lib/dovecot/deliver -f ${sender} -d ${recipient}
dovecot-other unix - n n - - pipe flags=DRhu user=vmail-other:vmail-other argv=/usr/lib/dovecot/deliver -c /etc/dovecot/other/dovecot.conf -f ${sender} -d ${recipient}
My fix is: I use filesystem ACLs and just set the ACLs of the auth-master socket after starting the first dovecot instance (which creates the socket). I.e. I run after starting dovecot (and waiting for a second...):
setfacl -m u:vmail-other:rw /var/run/dovecot/auth-master
This works only for filesystems with ACL support, of course. I use setfacl with ext2/3; other filesystem ACL tools might differ.
Oh, and thanks for dovecot and this supportive mailinglist btw. (even though this is my first post: hi everyone :) )
Greetings,
Jens