Switching Users
Once you have logged in to your desktop, you can switch to different user without having to log out or end your current user session. On GNOME you use the User Switcher tool, a GNOME applet on the panel. For KDE you use the Switch User entry on the Main menu.
User Switcher: GNOME
On GNOME, the switcher will appear on the panel as the name of the currently logged-in user. If you left-click the name, a list of all other users will be displayed. Check boxes next to each show which users are logged in and running. To switch a user, select the user from this menu. If the user is not already logged in, the login manager (the GDM) will appear and you can enter that user’s password. If the user is already logged in, then the Login window for the lock screen will appear (you can disable the lock screen). Just enter the user’s password.
The user’s original session will continue with the same open windows and applications running as when the user switched off. You can easily switch back and forth between loggedin users, with all users retaining their session from where they left off. When you switch off from a user, that user’s running programs will continue in the background.
Right-clicking the switcher will list several user management items, such as configuring the login screen, managing users, or changing the user’s password and personal information. The Preferences item lets you configure how the User Switcher is displayed on your panel. Instead of the user’s name, you could use the term Users or a user icon. You can also choose whether to use a lock screen when the user switches. Disabling the lock screen option will let you switch seamlessly between logged-in users.
Switch User: KDE
On KDE, the Switch User entry on the Main menu will display a list of users you can change to. You can also elect to start a different session, hiding your current one. In effect this lets you start up your desktop again as the same user. You can also lock the current session before starting a new one. New sessions can be referenced starting with the F7 key for the first session. Use CTRL-ALT-F7 to access the first session and CTRL-ALT-F8 for the second session.