[Dovecot] best choice of user database file to work with postfix?

[Phil Howard]

On Fri, Apr 23, 2010 at 2:49 AM, Rainer Frey <rainer.frey at inxmail.de> wrote:

> On Thursday 22 April 2010 18:15:18 Phil Howard wrote:
> [ ... all standard stuff that is well documented ... ]
>
> > 5.  Passwords stored encrypted, such as MD5.  And it should be a scheme
> > that both Postfix and Dovecot can use so I don't have keep two different
> > encryption schemes.
>
> Postfix doesn't need any password directly. It only authenticates a user
> with
> a password in one case: SMTP SASL authentication of submission users, and
> it
> uses the dovecot auth service for that and does not read the password
> database
> itself.
>

OK, so all that is in whatever SASL configuration, and so I'll be doing that
in Dovecot.

 It is not about supporting a certain database library. There is simply a
> difference in what Dovecot and Postfix need from a user/recipient database.
> Dovecot needs information like path to mailbox, uid/gid with which to put
> files into the mailboxes, extra configuration fields ... Therefore it uses
> a
> structured  multi-value format like the passwd-file. CDB or similar don't
> work
> like this, so dovecot can't easily support using the same CDB files as
> postfix.
>

Why not have all those fields combined into the value string you get from
CDB?  If it can do it from a line out of /etc/passwd then it can do it from
CDB (the value could simply be that same line ... or defined to be something
else more convenient).


Postfix only supports name:value tables, either to use the value
> (table-style
> lookup) or to check whether there is an entry for a name (list-style
> lookup).
> Therefore it only uses file databases with such a mapping. In the case of
> valid recipients which will be handed off to dovecot for delivery, it is
> such
> a simple list lookup.
>

The value can be a tuple (see above).  We're lucky that what Postfix needs
is "does this exist".  So it can just completely ignore the value and not
need any code to parse it.



> (If it interests you: the postfix virtual delivery agent needs very similar
> information to dovecot, but it uses several key:value maps for the
> different
> information, all with the recipient as key.)
>

I've run into that before.  I think it was the source of some difficulty.
In programming I've done, I've stored structured data in Berkeley DB and
never needed but one table/file per class of index.