[Dovecot] Getting rid of the common newbie problems

[Timo Sirainen]

I think the most common Dovecot newbie problems are:

 - Not looking at the (correct) logs for errors
 - Authentication problems
 - Mail location problems
 - Mail permission problems

Below are some of my ideas how I could stop people from asking these
questions with future Dovecot (v1.1+) releases. Suggestions welcome.
Distribution people especially should say if they're against some
change.

 * Logging

The log file problem is the most annoying one, because a lot of the
other problems can be solved once the admin figures out that Dovecot is
actually giving useful error messages. Often the admin is only looking
at the log file where "info" messages go (eg mail.log) because Dovecot
logs its startup message and login messages there, but not where the
errors go (eg mail.err). This has happened even with people who in
general are experienced sysadmins.

Logging to eg. /var/log/dovecot.log by default would be helpful here,
but it's probably better to log via syslog by default. Cyrus logs to
"local6" by default. Perhaps for Dovecot v1.1 I should make that the
default too? Looks like in my Debian system the info messages then go to
both /var/log/messages and /var/log/syslog. Error messages only go
to /var/log/syslog. So there still isn't by default a single log file
where the errors are logged, but it might help a bit.

 * Authentication

Authentication problems can usually be solved by telling the user to set
auth_debug_passwords=yes and looking at the logs. I'm not sure if
there's anything that can be helped in here. Except the logging message
could be updated a bit:

"Aborted login: user=<asdga>, method=PLAIN, rip=127.0.0.1,
lip=127.0.0.1, secured, 1 failed authentications"

So the last "n failed authentications" could be added, where n could
also be 0.

Another possibility would be to make Dovecot remember if there have been
any successful logins (/var/lib/dovecot/success file) and if not, give a
bit more helpful error messages:

 - Client gets: "NO Authentication failed. Refer to server log for more
information." instead of the normal "NO Authentication failed."
 - Log contains: "Aborted login: user=<asdga>, method=PLAIN,
rip=127.0.0.1, lip=127.0.0.1, secured, 1 failed authentications (set
auth_debug_passwords=yes to debug the problem)"

I'm not sure if this is a good idea.

 * Mail location

It seems to be difficult for some people to set mail_location. I don't
know if anything can be done before Dovecot v2.0 where I'll split it to
multiple settings, such as:

driver = maildir
root_dir = ~/Maildir
index_dir = /var/indexes/%u

Another problem that seems to be difficult to understand is why the mail
directory contains "HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB". The
whole userdb concept appears to be weird. This could anyway be fixed by
giving an error message earlier and failing the login with internal
error.

Probably the best place to give the error message would be already in
the userdb lookup in dovecot-auth, but that would require that
doveoct-auth knows if the home directory is really needed, and to give a
useful error message it would also need to tell where it's tried to be
used (mail_location, or some namespace's location, or ..). Probably too
much trouble to be worth it. So the next best thing is to give the error
when it's used:

"Home directory is used in mail_location, but userdb didn't return a
home directory"

It would be nice if it didn't say userdb, but rather the userdb's name.
I guess that would be possible if dovecot-auth told master (or deliver)
which userdb was used, but that would normally be just extra overhead.

 * Mail permissions

If mail location is difficult for some, then the concept of UIDs are how
they're used in Dovecot is pretty much impossible for some to
understand.

One of the problems is that there exists "dovecot" user. So people think
that their mails should be owned by the dovecot user. Although I've
mentioned in everywhere I can think of that this should not be done, it
won't help because either people won't read the pages or even if they
do, they somehow still fail to ignore it even though it's written in
bold.

So unless people (and most importantly, distributions) are against it, I
think the "dovecot" user should be renamed. "dovelogin" perhaps. In
future I might split dovecot-auth even more, and then I would like to
create a "doveauth" user as well.

Another possibility would be to drop the dovecot user completely and
instead use "nobody". That would mean that other nobody processes could
kill Dovecot's login processes, but that's pretty much it.

Once people understand that "dovecot" isn't the right user, they hit the
next problem: "How do I tell Dovecot to run as vmail user?" I can paste
links to wiki pages or tell them to "make userdb return uid=vmail", but
that just doesn't seem to get through. There needs to be an easier way,
and I think I figured out what it is:

Add new "mail_uid" and "mail_gid" settings to dovecot.conf. Deprecate
user_global_uid/gid in dovecot-ldap.conf and make all the userdbs
mention that the uid/gid returned by userdb can be used to override the
global mail_uid/gid. Perhaps also add "mail_home" template. This change
makes it unnecessary to have a userdb configured at all.

 - "How do I tell Dovecot to run as vmail user?"
 - "Set mail_uid = vmail" in dovecot.conf
 - "Thanks"

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