Document what to backup in Wallabag

Fixes issue #2479

docs/en/index.rst

@@ -46,6 +46,7 @@ The documentation is available in other languages:
    user/tags
    user/android
    user/parameters
+   user/backup
 
 .. _dev-docs:
 

docs/en/user/backup.rst

@@ -0,0 +1,26 @@
+Backup Wallabag
+===============
+Because sometimes you may do a mistake with your Wallabag and lose data or in case you need to move your Wallabag to another server you want to backup your data.
+This articles describes what you need to backup.
+
+
+Basic Settings
+--------------
+Wallabag stores some basic parameters (like SMTP server or database backend) in the file `app/config/parameters.yml`.
+
+Database
+--------
+As Wallabag supports different kinds of database, the way to perform the backup depends on the database you use, so you need to refer to the vendor documentation.
+
+Here's some examples:
+
+- Mysql: http://dev.mysql.com/doc/refman/5.7/en/backup-methods.html
+- Posgresql: https://www.postgresql.org/docs/current/static/backup.html
+
+sqlite
+~~~~~~
+To backup the sqlite database, you just need to copy the directory `data/db` from the Wallabag application directory
+
+Images
+------
+The images retrieved by Wallabag are stored under `data/assets/images`.