dovecot-request@dovecot.org wrote:

Date: Fri, 20 Oct 2006 13:26:03 +0100 (BST) From: David Lee t.d.lee@durham.ac.uk Subject: [Dovecot] 1.0.rc10 status report

1. "User unknown": We use NIS for our passwd information. On the earlier rc8 test we had had several occurences of "User unknown" (from "deliver") giving "dsn=5..." for perfectly valid users. So for this rc10 test I applied a local patch so these were reduced to "EX_TEMPFAIL" (dsn=4...). (This was triggered, as epected, a few times and subsequent delivery attemtps succeeded.) I strongly suspect that this is some sort of issue with FC5, probably "nscd" and nothing to do with dovecot. Hints would be nice, but from the dovecot perspective you may probably ignore this item.

I've had similar "User unknowns" with nscd in the past. I was using dovecot ->getpwent -> nscd -> nss_ldap -> LDAP. I found out that whenever the ldap server got restarted, nscd did not restart properly and immediately its permanent ldap connection, and was giving 'user unknown' replies at least for a few minutes. Restarting nscd would fix the problem immediately. Running without nscd
would also fix the problem. There was no problem with pam_ldap authentication. As a result, the system got ignorant of its uncached users for a few moments.

My workaround was a crontab that kept /etc/passwd up-to-date as well as an entry in the /etc/resolv.conf 'passwd: ldap files'

(cat /etc/passwd ; getent passwd ) |sort -u >/etc/passwd.tmp && mv /etc/passwd.tmp /etc/passwd

So should I have the indexes on the fileserver (one instance), or should they be on each cluster machine's private storage (possibly several instances; one per cluster machine)? The suggestion is that if you need to have mailboxes over NFS, use local disk for indexes. If you read the complete list archive you will find too many people that have had troubles with indexes over NFS. Local indexes have a performance penalty, only when you have access from different imap servers (especially concurrent) .

apap