Document ATTIC_PASSPHRASE

docs/faq.rst

@@ -7,7 +7,8 @@ Frequently asked questions
 Which platforms are supported?
 ------------------------------
 
-Currently Linux and MacOS X are supported.
+Currently Linux, FreeBSD and MacOS X are supported.
+
 
 Can I backup VM disk images?
 ----------------------------
@@ -15,6 +16,7 @@ Can I backup VM disk images?
 Yes, the :ref:`deduplication <deduplication_def>` technique used by |project_name|
 makes sure only the modified parts of the file are stored.
 
+
 Which file attributes are preserved?
 ------------------------------------
 
@@ -30,3 +32,13 @@ The following attributes are preserved:
 
 .. Note::
     POSIX Access Control Lists (ACL_) are not yet preserved.
+
+
+How can I specify the encryption passphrase programmatically?
+-------------------------------------------------------------
+
+The encryption passphrase can be specified programmatically using the
+`ATTIC_PASSPHRASE` environment variable. This is convenient when setting up
+automated encrypted backups. Another option is to use
+key file based encryption with a blank passphrase. For more details see
+:ref:encrypted_repos

docs/generalusage.rst

@@ -66,6 +66,10 @@ Passphrase based encryption
     PBKDF2_ key derivation function. This method is convenient to use and
     secure as long as a *strong* passphrase is used.
 
+    .. Note::
+        For automated backups the passphrase can be specified using the
+        `ATTIC_PASSPHRASE` environment variable.
+
 Key file based encryption
     This method generates random keys at repository initialization time that
     are stored in a password protected file in the ``~/.attic/keys/`` directory.