When you finish using your computer and leave the area, you should probably log out so that no one can wander in and gain access to your files, email account, etc. If you have a user name on a network, everything done on the computer with this identifier is considered your work. Imagine if someone were to enter incorrect data or to conduct improper behavior on your account, and it was traced back to you. Logging out helps keep the system secure.
An alternative to logging out is to lock the screen, as described in the next section, and unlock it when you come back. But logging out gives other people a chance to use your system.
Whereas logging out leaves your computer running, shutting down terminates all processing so that the hardware can be powered off. Many people let their Linux workstations run day and night, without shutting them down. In some organizations, your idle workstation joins in as part of a supercomputing grid during the evening hours. Since Linux computers can run months and even years without having to restart, you may not have to shut down your JDS system.
However, if you want to turn off your computer, you must first shut down JDS to ensure that you don’t lose any data or corrupt any files. Some computers automatically turn off the power at the end of the shutdown sequence. (Usually, the monitor is still running, though, and needs to be turned off by hand.) Other computers require that you manually turn off the power switch on the computer box.
If you switch off your computer before JDS has shut down—or if a power failure interrupts your work unexpectedly—you can lose data. In fact, even if you carefully save your documents, the data may not be safely stored to disk if your system powers down without shutting down JDS first. Many applications remember what you did between saves, and the next time you run the application they ask you whether you’d like to restore the data that you failed to save. But a clean shutdown is safer.
Both logging out and shutting down can be started through the same menu item: click on the Launch menu at the bottom left of the JDS panel and choose Log Out, as shown in Figure 2-3. This will bring you to the same JDS dialog box that is shown in Figure 2-4. It offers the following choices.
- Log Out
Choose this option to take you back to the Logon Screen, as shown in Figure 2-1. From there, you can choose to shut down the operating system or log on as another user (explained later in the chapter).
- Shut Down
Choose this option when you are ready to finish using your computer for the day and want to switch off the power. If your computer does not have the auto-power control enabled, JDS displays a message telling you to shut off your computer when it is safe to do so.
- Restart the Computer
Choose this option to restart the computer. In JDS, you usually need this option only after you make updates to the operating system. After completion of the update installation, the On-Line Update dialog may suggest you use this option.
- Cancel
Choose this option if you change your mind and do not want to restart the computer.
If you would like your applications to restart each time you log in, as you left them when you last logged out, you can set this up from the Launch menu. Select Preferences → Advanced → Sessions. In the resulting dialog box, click on the “Session options” tab in the upper-left corner. Click on the box “Automatically save changes to session” and close the box to save the setting.
An alternative to logging out is to lock the screen. This choice is usually taken by users when they plan to leave the computer briefly and need a convenient way to secure the screen. Sometimes JDS even locks the screen automatically when the computer has been idle for a long time; we show you how to control this behavior later in this section.
Locking the screen allows you to keep your session going, while preventing someone else from accessing your desktop. As discussed earlier, when you are in a work environment, you should leave your desktop protected while you are away.
To lock your screen, choose Launch → Lock Screen. Alternatively, if a Lock button exists on your panel, click on the “Lock this computer” button. To add the Lock button to the panel for this convenience, right-click on the panel and choose Add to Panel → Actions → Lock. When you lock your screen, the screen saver starts.
To unlock the screen, move your mouse over the screen saver to display the locked screen login window, shown in Figure 2-5. Enter your user name and password in the locked screen dialog, then press Return. Your desktop reappears.
To add additional security, some systems lock the screen after the system has been idle for a long time. Therefore, if you forget to lock your screen, while taking a break, helping a coworker, or leaving for any other reason, intruders are shut out.
If it is not already enabled, you can set up automatic locking by choosing Launch → Preferences → Display → Screensaver. Check the Lock Screen box and choose the number of minutes for the system to wait before the screen saver automatically starts on an idle desktop.