add title for section to set time

source/Installation/linux.rst

@@ -133,6 +133,11 @@ it's very important especially if you are connected to the net (ssh, ...)
 Administration
 ==============
 
+set the date and time
+=====================
+
+
+
 sudoers
 =======
 
@@ -171,6 +176,13 @@ only root can perform this command
 
 To take in account new user and group you need to logout and login again
 
+check you identity
+==================
+
+whoami
+
+id
+
 
 install package
 ===============