[Dovecot] Dovecot hanging up with many defunct processes

[Mayank Joshi]

Hi,

    I am in a very awkward situation and need some kind of immediate fix up.
I had installed dovecot in my organization as part of migration of email
server. The setup involves sendmail, dovecot (imaps+pop3s) and webmail
(squirrelmail) running on apache webserver. All was working fine until one
day I found a lot of defunct processes on system related to dovecot.
dovecot-auth, imap-login and imap were all defunct. The system is using
pam_ldap and nss_ldap to authenticate users to a Windows 2003 Active
Directory. Immediate restart of dovecot solved the problem for me that day,
however since then it's been about 3 times that I've faced this problem.
After visiting various forums I came to know one thing, that it has
something to do with pam_ldap and nss_ldap. However with UW-IMAP we were
using the same setup and we didn't find any problems there.
        It would be very kind of you, if you can help me out on this front
as apart from these mishaps the mail server is running perfectly fine and we
wish to continue using Dovecot for our setup in future as well.
        Following is the system details:

1) OS: RHEL4 (Kernel - 2.6.9-5.ELsmp)
2) Dovecot: Dovecot (Version - 1.0.3)
3) Following is dovecot configuration:
     log_path: /var/log/dovecot.log
     protocols: imaps pop3s
     ssl_cert_file: /usr/share/ssl/certs/imapd.pem
     ssl_key_file: /usr/share/ssl/private/imapd.pem
     login_dir: /usr/local/var/run/dovecot/login
     login_executable(default): /usr/local/libexec/dovecot/imap-login
     login_executable(imap): /usr/local/libexec/dovecot/imap-login
     login_executable(pop3): /usr/local/libexec/dovecot/pop3-login
     max_mail_processes: 10240
     mail_location: mbox:~/mail:INBOX=/var/mail/%u
     mail_executable(default): /usr/local/libexec/dovecot/imap
     mail_executable(imap): /usr/local/libexec/dovecot/imap
     mail_executable(pop3): /usr/local/libexec/dovecot/pop3
     mail_plugin_dir(default): /usr/local/lib/dovecot/imap
     mail_plugin_dir(imap): /usr/local/lib/dovecot/imap
     mail_plugin_dir(pop3): /usr/local/lib/dovecot/pop3
     pop3_uidl_format(default):
     pop3_uidl_format(imap):
     pop3_uidl_format(pop3): %08Xu%08Xv
     auth default:
     passdb:
         driver: pam
     userdb:
         driver: passwd
4) Dovecot's PAM file (/etc/pam.d/dovecot)
     #%PAM-1.0
     auth    required pam_ldap.so
     account required pam_ldap.so
     session required pam_mkhomedir.so skel=/etc/skel umask=0077
     session required pam_ldap.so

As far as I feel it's problem with pam_ldap not able to authenticate against
Windows 2003 Active Directory due to some reason or the other. However I'm
not sure why is this happening.


Regards,

Mayank Joshi.