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

A user database lookup typically returns <uid, gid, home and mail>
[UserDatabase.txt] fields. Other possibilities are:

 * *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.
    * This field is called *system_user* in v1.1 and older.
 * *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). (v1.2+)
 * *uidgid_file*: Get uid and gid for user based on the given filename. (v1.1+)

 * It's possible to override settings from 'dovecot.conf'.

These fields can be returned the exact same way as uid, gid, home and mail
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=maildir:storage=1024' value and the userdb lookup
returns 'quota=maildir:storage=2048', the original quota setting gets
overridden. In fact if the lookup always returns a quota field, there's no
point in having the quota setting in 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. All actual settings are first placed into environment variables. The
    environment name may be different than the setting name.
 2. Everything inside plugin section is placed into environment variables.
    <%variables> [Variables.txt] in values are expanded first.
 3. Everything from userdb lookup is placed into environment variables.
 4. At this point if <post-login scripting is used> [PostLoginScripting.txt],
    it may modify the environment if wanted.
 5. imap/pop3 reads the settings from environment variables. It doesn't matter
    how they got there, they're read the exact same way.

At each step if the environment variable already exists, it's replaced with the
new value (ie. the setting is overridden).

Note that

 * If you want to override a setting from userdb you must use its environment
   name, not the setting name. See <PostLoginScripting.txt> for how to find out
   what the environment is named.
 * Boolean settings are checked simply by the environment variables' existence
   and their values are ignored. For example having a userdb lookup return
   'mmap_disable=no' would still enable it.

Examples
--------

SQL
---

dovecot-sql.conf:

---%<-------------------------------------------------------------------------
# NOTE: \ line splitting works only with v1.1+. The quota_rule is also for
v1.1+.
user_query = SELECT home, uid, gid, \
  '*:storage=100M' as quota_rule, mail_plugins \
  FROM users WHERE userid = '%u'
---%<-------------------------------------------------------------------------

LDAP
----

dovecot-ldap.conf:

---%<-------------------------------------------------------------------------
user_attrs =
homeDirectory=home,uidNumber=uid,gidNumber=gid,quotaDovecot=quota,mail_plugins
---%<-------------------------------------------------------------------------

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].

---%<-------------------------------------------------------------------------
# v1.0 quota format:
user:{plain}pass:1000:1000::/home/user::userdb_mail=mbox:~/mail
userdb_quota=maildir:storage=102400
# v1.1 quota format:
user:{plain}pass:1000:1000::/home/user::userdb_mail=mbox:~/mail
userdb_quota_rule=*:storage=100M
user2:{plain}pass2:1001:1001::/home/user2::userdb_mail=maildir:~/Maildir
userdb_quota_rule=*:storage=200M
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2011-05-11 04:42)
