partly merged with docs-essential-guide-r2

console server related items are not added to master

docs/login/login.rst

@@ -30,7 +30,11 @@ before you can log in with your account.
    anonymous user may not be allowed. In that case, please contact administrator
    of your system.
 
-
+.. note::
+   To prevent malicious users from guessing user's password, password should be longer
+   than 8 characters with at least one alphabet(s), number(s), and special
+   character(s).
+
 Login
 -----
 
@@ -41,6 +45,11 @@ entered.
 .. note::
    Depending on the installation and setup environment of the Console Server,
    the endpoint might be pinned and not configurable.
+
+.. note::
+   Backend.AI keeps the user's password securely through a one-way hash. BCrypt,
+   the default password hash of BSD, is used, so even the server admins cannot
+   know the user's password.
 
 After login, you can check the information of the current resource usage in
 the Summary tab.
@@ -49,7 +58,7 @@ By clicking the icon in the upper-right corner, you will see sub menus. You
 can logout by selecting the Log Out menu.
 
 .. image:: signout_button.png
-   :width: 300
+   :width: 600
    :align: center
    :alt: Signout button
 
@@ -71,3 +80,10 @@ administrator.
 .. note::
    This is also a modular feature, so changing password may not be possible in
    some systems.
+
+.. warning::
+   If login failure occures more than 10 times consecutively, access
+   to the endpoint is temporarily restricted for 20 minutes for security
+   reasons. If the access restriction continues on more than 20 minutes, please contact
+   your system administrator.
+