David Lee wrote:
We're running dovecot on Fedora Core 5 (FC5), with passwd map details supplied by NIS. We have found that "nscd" sometimes thinks that a username is invalid, even though it is valid. So when "deliver" attempts a delivery to the INBOX of that username, it receives "user unknown" from the name service, and then does a 5xx permanent failure of valid email.
From the user perspective "The System" has incorrectly rejected perfectly valid incoming email. It is rare, but it does occasionally happen on large, busy systems.
We don't use "deliver" (just use Exim) but we build a static passwd-file userdb from NIS overnight and use PAM for authentication (via pam_ldap to Active Directory, but it works with pam_unix too). We did this for a performance boost as Dovecot then caches the userdb, rather than having to wait for a NIS lookup each time, but I'd expect it to iron out problems with deliver/nscd as well. While the passwords could change any time, userdb information generally doesn't happen that often, and it only takes a few seconds to rebuild manually if a new user has to be added quickly.
Chris
-- --+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+- Christopher Wakelin, c.d.wakelin@reading.ac.uk IT Services Centre, The University of Reading, Tel: +44 (0)118 378 8439 Whiteknights, Reading, RG6 2AF, UK Fax: +44 (0)118 975 3094