User database extra fields
==========================

A user database lookup typically returns <uid, gid and home> [UserDatabase.txt]
fields, as per traditional /etc/passwd lookups. Other fields may also be stored
in the userdb, and these are called 'extra fields'. Possibilities are:

 * *mail*: <Mail location> [MailLocation.txt], overrides the global
   'mail_location' setting.
 * *nice*: Set the mail process's priority to be the given value.
 * *chroot*: Chroot to given directory. Overrides 'mail_chroot' setting in
   'dovecot.conf'.
 * *system_groups_user*: Specifies the username whose groups are read from
   '/etc/group' (or wherever NSS is configured to taken them from). The logged
   in user has access to those groups. This may be useful for shared mailboxes.
 * *userdb_import*: This allows returning multiple extra fields in one
   TAB-separated field. It's useful for userdbs which are a bit less flexible
   for returning a variable number of fields (e.g. SQL).
 * *uidgid_file*: Get uid and gid for user based on the given filename.
 * It's possible to override settings from 'dovecot.conf' (most commonly
   quota_rule to set per-user quota limits or also plugin-settings).
 * *user*: User can be overriden (normally set in <passdb>
   [PasswordDatabase.txt]).
 * The extra fields are also passed to <post-login scripts>
   [PostLoginScripting.txt].

The following suffixes added to a field name are handled specially:

 * *:protected*: Set this field only if it hasn't been set before.
 * *:remove*: Remove this field entirely.

These fields can be returned the exact same way as uid, gid, and home fields.
Below are examples for some user databases.

Overriding settings
-------------------

Most commonly settings are overridden from plugin section. For example if your
plugin section has 'quota_rule=*:storage=100M' value and the userdb lookup
returns 'quota_rule=*:storage=200M', the original quota setting gets
overridden. In fact if the lookup always returns a 'quota_rule' field, there's
no point in having the 'quota_rule' setting in the plugin section at all,
because it always gets overridden anyway.

To understand how imap and pop3 processes see their settings, it may be helpful
to know how Dovecot internally passes them:

 1. First all actual settings are first read into memory.
 2. Next all the extra fields returned by userdb lookup are used to override
    the settings. Any unknown setting is placed into the plugin {} section
    (e.g.'foo=bar' will be parsed as if it were 'plugin { foo=bar }').
 3. Last, if <post-login scripting is used> [PostLoginScripting.txt], it may
    modify the settings if wanted.

If you want to override settings inside sections, you can separate the section
name and key with '/'. For example:

---%<-------------------------------------------------------------------------
namespace default {
  inbox = yes
  separator = .
  location = maildir:~/Maildir
}
---%<-------------------------------------------------------------------------

The separator setting can be overridden by returning
'namespace/default/separator=.' extra field.

Examples
--------

SQL
---

dovecot-sql.conf:

---%<-------------------------------------------------------------------------
user_query = SELECT home, uid, gid, \
  CONCAT('*:bytes=', quota_bytes) AS quota_rule, \
  separator AS "namespace/default/separator" \
  FROM users WHERE username = '%n' and domain = '%d'
---%<-------------------------------------------------------------------------

LDAP
----

dovecot-ldap.conf:

---%<-------------------------------------------------------------------------
user_attrs = \
  =home=%{ldap:homeDirectory}, \
  =uid=%{ldap:uidNumber},
  =gid=%{ldap:gidNumber},
  =quota_rule=*:bytes=%{ldap:quotaBytes},
  =namespace/default/separator=%{ldap:mailSeparator}
---%<-------------------------------------------------------------------------

passwd-file
-----------

Below are examples that show how to give two userdb extra fields ("mail" and
"quota"). Note that all userdb extra fields must be prefixed with "userdb_",
otherwise they're treated as <passdb extra fields>
[PasswordDatabase.ExtraFields.txt].

---%<-------------------------------------------------------------------------
user:{plain}pass:1000:1000::/home/user::userdb_mail=mbox:~/mail
userdb_quota_rule=*:storage=100M userdb_namespace/default/separator=/
user2:{plain}pass2:1001:1001::/home/user2::userdb_mail=maildir:~/Maildir
userdb_quota_rule=*:storage=200M
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2017-05-11 04:42)