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User's Guide (Obsolete Documentation) (Obsolete Documentation)
Chapter 4 - Starting and Stopping the System and Graphical Interface

Like any version of Linux, Debian has strict procedures for starting and stopping a system. These procedures are part of the operating system's security features. They also prevent accidental damage to the system.

To start your computer, you must choose the operating system to load from the boot manager, and then log in to a user account.

To stop your computer, you must log out of the user account, then halt or reboot the system.

This chapter explains:

4.1 Working With User Accounts

Linux is designed for multiple users. To use the system, you must log in with a user account. To use an account, you must know both the user name and the password.

User accounts are organized into groups of accounts with similar access to the system. The software and the hardware you can use depends on the user account that you are using and the groups to which it belongs.

For more information,

When you install Debian, create at least two user accounts: a regular user account for everyday computing, and a root account for system administration. Normally, you also want one regular user account for each person who uses the system.

4.1.1 Understanding Regular User Accounts

A regular account is used for everyday computing. Each account has a home directory. By default, users' home directories are beneath the / home directory. This home directory is usually the same as the user name for the account.

When you are logged in with an account, you usually can:

On some systems, the system administrator may choose to make basic system files unreadable by regular users.

Accounts may annoy those familiar with other operating systems. However, user accounts have several advantages:

4.1.2 Understanding the Root Account

The root account has full access to all software and hardware on the system. In most cases, it should be the only account that has full access. For this reason, the root user is sometimes called the super user or privileged user. The root user's home directory is /root.


The /root directory is different from the root directory at the top of the Linux directory tree. Nor is it the same as the root partition - the partition that the root directory is on.

To avoid damaging your system, take the following precautions when using the root account:

Using the Boot Loader


Many users have multiple operating systems or Linux kernels on the same computer. Using a boot loader, you can choose which operating system or kernel to start your computer with.

Debian uses grub (Grand Unified Boot Loader). However, other boot loaders are widely used, including lilo (the Linux Loader).

grub is the first thing that you see when starting a Debian system.

You can edit grub to display any installed operating system or kernels. Your Debian system also includes a single-user mode. The single-user mode starts the machine with a basic system that the root user can use for troubleshooting.

To choose an operating system from grub , do one of the following:

In either case, Debian starts. After processes are started and some tests are run, the graphical display starts and the log in screen opens.

You can reconfigure grub and add other operating systems to it. See Configuring the Boot Loader, Section 13.3.4.

4.2 Logging in to Debian


After Debian has started its initial processes and run some checks, the log in screen opens.

Logging in is the process of entering your user account and your password.


You cannot bypass this process, the way you can in some operating systems.

By default, you log in graphically. However, you can also configure Debian to start in a command line instead.

4.2.1 Logging in Graphically

From the login window:


Use the root account only for configuration or administration work.

4.2.2 Logging in from a Command Line

You can log in from a command line if you configure Debian not to start the graphical interface automatically.

You can also start Debian in single-user mode, which does not include the graphical interface. If you press Ctrl-D from the log prompt in single-user mode, the graphical interface starts.


Use the root account only for configuration or administration work.

4.3 Shutting Down Debian

Linux is generally running many processes at once. Many of these run in the background, where they are easy to forget. For this reason, shutting down the system properly is essential.

A proper shutdown is often called a graceful shutdown or exit. During a graceful shutdown:


If you do not shut down properly, you may damage the operating system or lose files. At best, the next time you start your computer, you have a long delay while the root partition is checked.

You can shut down from:

4.3.1 Shutting Down from the Desktop


If you do not shut down properly, then you risk damaging the operating system. Even if no damage is done, your system checks the root partition before restarting.

A quicker alternative is to open the command line and shut down from there. See Shutting Down Debian, Section 4.3-check: enabled?

4.3.2 Shutting Down From the Command Line


Use the shutdown command to give regular users time to save their work.


If you do not shut down properly, then you risk damage the operating system. Even if you don't, your system will check and, if necessary, repair the root partition before restarting.

4.3.3 Shutting Down From the Keyboard

4.4 Starting and Shutting Down the Graphical Interface

Linux uses the X Window system for a graphical interface, such as a desktop and/or a window manager. See Understanding Graphical Interfaces, Section 6.1.

You can choose to start a graphical interface automatically when you start your computer. This is the default setup for Debian. Alternatively, you can start the X Window system from the command line.

4.4.1 Starting a Graphical Interface From the Command Line

You must have the X Window System installed as well as a desktop and/ or window manager.


The X Window System is not loaded if you are starting from single-user mode.

4.4.2 Exiting the Graphical Interface

You can:

4.4.3 Keeping the X Window System Running in the Background

4.4.4 Closing Down an X Window System

4.5 Changing User Accounts

From both the command line and the desktop, you can logout as one user, then login as another. However, a more convenient way to change accounts is to use the su command ("switch user" or "set user").

This command is especially useful if you need to log in briefly as the root user while using a graphical interface. However, to use it effectively, you need to be comfortable working from the command line.

To change user accounts:


You have changed accounts only for the command line you are using. If you are running a desktop, then you are still logged in with your original account in other windows.

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User's Guide (Obsolete Documentation) (Obsolete Documentation)

Version: 1.00p00, 2009.07.21-11:14

Progeny Linux Systems, Inc.