

Virtual Users
=============


There are many ways to configure Dovecot to use virtual users. If you have no idea how you want your users to be configured, select some >>HOWTO<< and follow its instructions. 
Users are often categorized as being either system users (in '/etc/passwd') or virtual users (not in '/etc/passwd'). However from Dovecot's point of view there isn't much of a difference between them. If a >>passwd<< lookup and a >>SQL<< lookup return the same >>userdb<< information, Dovecot's behavior is identical. 


Password and user databases
===========================


Dovecot supports many different >>password databases<< and >>user databases<<. With virtual users the most commonly used ones are >>LDAP<<, >>SQL<< and >>passwd-file<<. The databases usually contain the following information: 

 * Username 
 * Password 
 * UNIX User ID (UID) and primary UNIX Group ID (GID) 
 * Home directory and/or mail location 


Usernames and domains
=====================


Dovecot doesn't care much about domains in usernames. IMAP and POP3 protocols currently have no concept of "domain", so the username is just something that shows up in your logs and maybe in some configuration, but they have no direct functionality. 
So although Dovecot makes it easier to handle "user@domain" style usernames (eg. %n and %d >>variables<<), nothing breaks if you use for example "domain%user" style usernames instead. However some >>authentication mechanisms<< do have an explicit support for realms (pretty much the same as domains). If those mechanisms are used, the username is changed to be "user@realm". 
And of course there's no need to have domains at all in the usernames. 


Passwords
=========


The password can be in >>any format that Dovecot supports<<, but you need to tell the format to Dovecot because it won't try to guess it. SQL and LDAP configuration files have 'default_pass_scheme' setting for this. If you have passwords in multiple formats, or the passdb doesn't have such a setting (eg. passwd-file), you'll need to prefix each password with "{<scheme>}", for example "{PLAIN}plaintext-password" or "{PLAIN-MD5}1a1dc91c907325c69271ddf0c944bc72". 


UNIX UIDs
=========


The most important thing you need to understand is that *Dovecot doesn't access the users' mails as the /dovecot/ user*! So *don't* put /dovecot/ into /mail/ group, and don't make mails owned by /dovecot/ user. That will only make your Dovecot installation less secure. 
So, if not the /dovecot/ user, what then? You can decide that yourself. You can create for example one /vmail/ user which owns all the mails, or you can assign a separate UID for each user. See >>UserIds#mailusers<< for more information about different ways to allocate UIDs for users. 


UNIX GIDs
=========


Unless you're using >>shared mailboxes<< and multiple UIDs, it doesn't really matter what GIDs you use. You can for example use a single GID for all users, or create a separate GID for each user. See >>UserIds#gids<< for more information. 
 

Home directories
================


Some people are opposed to the idea of virtual users having home directories, but no matter what you call it, it's a good idea to have a directory where user-specific configuration and other state is stored. Currently the home directory is used for two purposes: 

 * Debugging: If imap or pop3 process crashes, the core file is written to the user's home directory. Without a home directory it will be more difficult to debug the crashes. See http://www.dovecot.org/bugreport.html for more information. 
 * >>Sieve plugin<< stores the user's Sieve script and a mail duplicate database in the user's home directory. It's not possible to use the Sieve plugin without users having a home directory. 
In future there will probably be other uses as well. 
The directory layouts for home and mail directories could look like one of these (in the preferred order): 

 1. Mail directory under home, for example: home='/var/mail/user/' mail='/var/mail/user/mail/' 
 2. Completely distinct home and mail directories: home='/home/virtual/user/' mail='/var/mail/user/' 
 3. Home directory under mail, for example: 

 * Maildir: home='/var/mail/user/home/' mail='/var/mail/user/' 
 * mbox: home='/var/mail/user/.imap/.imap/' mail='/var/mail/user/' 

 * The '.imap/.imap/' is the only safe name for the home directory. Otherwise it's possible that the home directory either shows up as a normal mailbox, or that it can be deleted by creating and deleting a mailbox (eg. '.imap/home/' directory gets deleted with "DELETE home" IMAP command). 


 * Home directory is the same as mail directory. The problem with this is that the created files may show up as mailboxes. This is especially problematic with mbox. 


Mail location
=============


The userdb can return 'mail' >>extra field<< to override the default 'mail_location' setting. Usually you shouldn't need this. 


Examples
========




Dynamic passwd-file locations
=============================



---%<-------------------------------------------------------------------------
mail_location = maildir:/home/%d/%n/Maildir
userdb passwd-file {
  args = /home/%d/etc/passwd
}
passdb passwd-file {
  args = /home/%d/etc/shadow
}
---%<-------------------------------------------------------------------------

In the above examples users are expected to log in as "user@domain". Their mail is kept in their home directory at '/home/<domain>/<username>/Maildir'. 
The usernames in the passwd and shadow files are expected to contain only the user part, no domain. This is because the the path itself already contained %d to specify the domain. If you want the files to contain full user@domain names, you can use %0.d instead of %d. 


static userdb
=============


Many people store only usernames and passwords in their database and don't want to deal with UIDs or GIDs. In that case the easiest way to get Dovecot running is to use the >>static userdb<<: 

---%<-------------------------------------------------------------------------
mail_location = maildir:~/Maildir
passdb pam {
}
userdb static {
  args = uid=vmail gid=vmail home=/var/mail/virtual/%d/%n
}
auth_userdb = 
---%<-------------------------------------------------------------------------

This makes Dovecot look up the mails from '/var/mail/virtual/<domain>/<user>/Maildir/' directory, which should be owned by vmail user and vmail group. 


Existing virtual user management software
=========================================



 * VPopMail [None]: Dovecot >>supports VPopMail directly<<. 
 * Linuxconf [None]: See >>Migration/Linuxconf<< 
 * Also see the Examples / Scenarios in >>FrontPage<< 

(This file was created from the wiki on 2007-12-11 04:42)
