hostnamectl: add --pretty and --static examples (#5203)

pages/linux/hostnamectl.md

@@ -8,4 +8,12 @@
 
 - Set the hostname of the computer:
 
-`sudo hostnamectl set-hostname "{{some_hostname}}"`
+`sudo hostnamectl set-hostname "{{hostname}}"`
+
+- Set a pretty hostname for the computer:
+
+`sudo hostnamectl set-hostname --static "{{hostname.example.com}}" && sudo hostnamectl set-hostname --pretty "{{hostname}}"`
+
+- Reset hostname to its default value:
+
+`sudo hostnamectl set-hostname --pretty ""`