userdb lookup not possible with only userdb prefetch

[Alexander Dalloz]

Am 07.12.2014 um 00:22 schrieb Yves Goergen:
> Hello,
>
> I am setting up a new server and migrating my Dovecot 1.2.9 config to
> the new 2.2.9 version. There wasn't much to keep from the old version so
> I had to recreate the config from scratch. Now I think I'm done but I
> can't login to IMAP. The log says this:
>
>> dovecot: auth: Error:
>> prefetch(box@****.de,2001:****:7765,<bzAOP5QJXwAgAQpgEAXJAZyOMB1qBXdl>):
>> userdb lookup not possible with only userdb prefetch
>> dovecot: auth: Error:
>> userdb(box@****.de,2001:****:7765,<bzAOP5QJXwAgAQpgEAXJAZyOMB1qBXdl>):
>> user not found from userdb prefetch
>> dovecot: imap: Error: Authenticated user not found from userdb, auth
>> lookup id=178651137 (client-pid=13711 client-id=1)
>> dovecot: imap-login: Internal login failure (pid=13711 id=1) (internal
>> failure, 1 successful auths): user=<box@****.de>, method=PLAIN,
>> rip=2001:****:7765, lip=2a01:****:2, mpid=13717, TLS,
>> session=<bzAOP5QJXwAgAQpgEAXJAZyOMB1qBXdl>
>
> That doesn't help me a lot. Here's parts of my configuration, dumped
> with 'dovecot -n':
>
>> # 2.2.9: /etc/dovecot/dovecot.conf
>> # OS: Linux 3.13.0-40-generic x86_64 Ubuntu 14.04.1 LTS
>> auth_mechanisms = plain login
>> disable_plaintext_auth = no
>> namespace inbox {
>>   inbox = yes
>>   location =
>>   mailbox Drafts {
>>     special_use = \Drafts
>>   }
>>   mailbox Junk {
>>     special_use = \Junk
>>   }
>>   mailbox Sent {
>>     special_use = \Sent
>>   }
>>   mailbox "Sent Messages" {
>>     special_use = \Sent
>>   }
>>   mailbox Trash {
>>     special_use = \Trash
>>   }
>>   prefix =
>> }
>> passdb {
>>   args = /etc/dovecot/dovecot-sql.conf.ext
>>   driver = sql
>> }
>> plugin {
>>   quota = maildir
>> }
>> protocols = imap pop3
>> userdb {
>>   driver = prefetch
>> }
>> protocol imap {
>>   mail_max_userip_connections = 100
>>   mail_plugins = quota imap_quota
>> }
>
> What's the problem here? How can I resolve this issue?

You did fulfill the requzirements for prefetch to work documented in the 
wiki?

http://wiki2.dovecot.org/UserDatabase/Prefetch

Alexander