'doveadm expunge' with -A and userdb { driver = passwd }

[Grant]

>>>> But I don't have an /etc/dovecot/users file.  I also don't seem to
>>>> have any mail user uid lower than 1000, but I do have some users above
>>>> 1000 which aren’t mail users (nobody, etc).
>>>
>>> Hello Grant,
>>>
>>> So as to avoid any ambiguity, could you post the output of "doveconf -n"?
>>
>>
>> Sure, here it is:
>>
>> # doveconf -n
>> # 2.2.16: /etc/dovecot/dovecot.conf
>> # OS: Linux x86_64 Gentoo Base System release 2.2
>> listen = 127.0.0.1
>> mail_location = maildir:~/.maildir
>> […]
>> passdb {
>> args = *
>> driver = pam
>> }
>> passdb {
>> args = scheme=CRYPT username_format=%u /etc/dovecot/users
>> driver = passwd-file
>> }
>> […]
>> userdb {
>> driver = passwd
>> }
>> userdb {
>> args = username_format=%u /etc/dovecot/users
>> driver = passwd-file
>> }
>
> Thank you, Grant.
>
> It thus appears that your server is configured to make use of system users, for both user authentication and user lookup. That you don’t have a /etc/dovecot/users file just means that the system is the only source for user information.
>
> You may find more details at http://wiki2.dovecot.org/Authentication/MultipleDatabases.
>
> And yes, the warning about doveadm’s -A option thus appears to be relevant in your case.


In that case it sounds like my best options would be to either
continue expunging old mail with a separate line for each user or
switch to /etc/dovecot/users for user lookup and maintain a list of
mail users there so I can use doveadm -A.  How can I switch to
/etc/dovecot/users?

- Grant