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+System Users
+============
+
+System users are typically defined in '/etc/passwd' file, but this isn't
+necessary. Using NSS [http://en.wikipedia.org/wiki/Name_Service_Switch] you can
+configure the lookups to be done from elsewhere (e.g. LDAP). See <passwd>
+[AuthDatabase.Passwd.txt] userdb configuration for how to set this up.
+Especially if you're using nss_ldap you must set 'blocking=yes'.
+
+System users usually have their own separate user IDs (UIDs). This is good from
+security point of view, because it means that the kernel will also prevent
+users from accessing each others' mails.
+
+If the users have direct write access to the mail files (eg. the users have
+shell access), they can easily cause all sorts of mailbox corruptions. That may
+generate all kinds of error messages to Dovecot's error logs, so it may be
+sometimes difficult to tell if there really is a problem or if user is just
+doing something stupid.
+
+If users are going to access the mailboxes with other software than Dovecot,
+it's important to make sure that their mailbox accesses are compatible. This
+mostly means that with mboxes you must make sure that everyone uses the <same
+locking methods in the same order> [MailboxFormat.mbox.txt].
+
+Authentication
+--------------
+
+Admins often wish to use different passwords for IMAP and POP3 than for other
+services (eg. SSH), because IMAP and POP3 clients often send the password
+unencrypted over the internet without even bothering to give users any
+warnings. Dovecot can easily support non-system passwords for system users.
+
+If you wish to use system passwords, you'll want to use one of these passdbs:
+
+ * <PAM> [PasswordDatabase.PAM.txt]: Most commonly used in Linux and BSDs
+   nowadays.
+ * <BSDAuth> [PasswordDatabase.BSDAuth.txt]: BSD authentication is used by
+   OpenBSD.
+ * <Passwd> [AuthDatabase.Passwd.txt]: System users (NSS, '/etc/passwd', or
+   similiar). This may work instead of PAM (mostly in some BSDs).
+ * <Shadow> [PasswordDatabase.Shadow.txt]: Shadow passwords for system users
+   (NSS,'/etc/shadow' or similiar). Deprecated by PAM nowadays, but it should
+   work with Linux and Solaris.
+
+If you wish to use non-system passwords, you can use pretty much any of the
+Dovecot's <password databases> [PasswordDatabase.txt], but for simple
+installations you'll probably want to use <passwd-file>
+[AuthDatabase.PasswdFile.txt].
+
+<User database> [UserDatabase.txt] for system users is always <passwd>
+[AuthDatabase.Passwd.txt].
+
+Mail Location
+-------------
+
+Usually UNIX systems are configured by default to deliver mails to
+'/var/mail/username' or '/var/spool/mail/username' mboxes. You may decide to
+use these, or use <maildir> [MailboxFormat.Maildir.txt] format instead.
+
+Dovecot detects the mailbox format and location automatically if
+'mail_location' setting isn't set, but it's still a good idea to explicitly
+tell Dovecot where to find the mails. This makes it sure that Dovecot behaves
+correctly also when the user's mailbox doesn't exist at the moment (eg. a new
+user). If Dovecot can't figure out where the existing mails are, it simply
+gives an error message and quits. It never tries to create a missing mailbox
+when autodetection is used.
+
+See <MailLocation.txt> for more information how to configure the mailbox
+location. Below are the highlights for mbox and maildir.
+
+mbox
+----
+
+The '/var/mail/username' mbox is called user's INBOX. IMAP protocol supports
+multiple mailboxes however, so Dovecot needs some directory where to store the
+other mailboxes. Typically they're stored in '~/mail/' or '~/Mail/' directory.
+All of these locations are included in mailbox location autodetection. You can
+specify them manually with:
+
+---%<-------------------------------------------------------------------------
+mail_location = mbox:~/mail:INBOX=/var/mail/%u
+---%<-------------------------------------------------------------------------
+
+Remember that the first path after 'mbox:' is the mailbox root directory, never
+try to give 'mbox:/var/mail/%u' because that just isn't going to work (unless
+you really want to store mails under '/var/mail/%u/' directory).
+
+If you're also using other software than Dovecot to access mboxes, you should
+try to figure out what locking methods exactly they're using and update
+'mbox_read_locks' and 'mbox_write_locks' settings accordingly. See locking
+section in <mbox> [MailboxFormat.mbox.txt] for more information.
+
+Maildir
+-------
+
+Maildir is typically stored in '~/Maildir' directory. You can specify this
+manually with:
+
+---%<-------------------------------------------------------------------------
+mail_location = maildir:~/Maildir
+---%<-------------------------------------------------------------------------
+
+Chrooting
+---------
+
+Dovecot, including several other software, allow using "/./" in home directory
+path to specify the chroot path. For example '/home/./user' would chroot to
+'/home'. If you want to enable this for Dovecot, add the chroot path to
+'valid_chroot_dirs' setting ('/home' in the previous example). If this isn't
+done, Dovecot just ignores the "/./".
+
+(This file was created from the wiki on 2019-06-19 12:42)