Learning Red Hat Linux (3rd Edition) [Electronic resources] نسخه متنی

9.1 Configuring Red Hat Linux by Using the System Settings Menu

The GNOME and KDE System Settings menu provides
access to 15 utilities that help you configure your system. Chapter 8 explained one of these, the package management
tool. The tools available are:

Authentication

Provides access to the Authentication Configuration tool, which lets
you configure password settings

Date & Time

Provides access to the Date/Time Properties tool, which lets you
configure the time zone, date, and time

Display

Provides access to the Display Settings tool, which lets you
configure monitor resolution, color depth, and other display
characteristics

Keyboard

Provides access to the Keyboard tool, which lets you choose the
keyboard appropriate to your system

Language

Provides access to the Language Selection tool, which lets you choose
the current language from among those for which
you've installed support

Login Screen

Provides access to the GDM (GNOME Display Manager) Setup tool, which
lets you configure how people log in under X

Mail Transport Agent Switcher

Provides access to the redhat-switchmail tool, which lets you choose
between the Sendmail and Postfix mail servers

Mouse

Provides access to the Mouse Configuration took, which lets you
choose the mouse appropriate to your system and enable or disable
3-button emulation

Network

Provides access to the Network Configuration tool, which lets you
configure network, modem, VPN (virtual private network), and wireless
connections and related settings

Packages

Provides access to the Package Management tool, which lets you
install and remove RPM packages

Printing

Provides access to the Red Hat Printer Config tool, which lets you
configure printers and control print queues

Root Password

Provides access to a tool that enables you to change the root password

Security Level

Provides access to the Security Level Configuration tool, which lets
you configure a firewall to protect your system from network attacks

Soundcard Detection

Provides access to the Sound Card Configuration tool, which lets you
configure and verify the operation of your sound card

Users and Groups

Provides access to the Red Hat User Manager, which lets you configure
user accounts and groups

Depending on the packages installed on your system, you may see fewer or more items on the System Settings menu.

In addition, the Extras menu contains a System Settings submenu, on
which you can find two more tools: Desktop Switching Tool and Printer
System Switcher. The Desktop Switching Tool lets you choose between
the GNOME and KDE desktop. The Printer System Switcher lets you
choose between the LPRng and CUPS printing system. Neither tool will
let you choose a facility that's not installed. So,
for example, unless you've installed both LPRng and
CUPS, the Printer System Switcher tool won't
actually function.

Most of the System Settings tools function like similar steps in the
Red Hat Linux installation procedure. This section focuses on tools
that do not resemble installation procedure steps, namely:

GDM Setup tool

redhat-switchmail tool

Red Hat Printer Config tool

Sound Card Configuration tool

Red Hat User Manager

Desktop Switching Tool

The Network Configuration tool provides many settings and functions.
Explanation of the Network Configuration tool is deferred to
Chapter 10 and Chapter 11.
Similarly, explanation of the redhat-switchmail tool is deferred to
Chapter 12

9.1.1 Setting Up X Logins

The GDM Setup tool, accessible via System
Settings Login Screen from the GNOME or KDE menu,
lets you specify options related to X logins. Figure 9-1 shows the tool. Most of the options are
cosmetic. For example, you can choose whether times are displayed in
12-hour or 24-hour format. However, the Security and
XDMCP tabs provide options that you should
consider changing.

Figure 9-1. The GDM Setup tool

By
default, the XDMCP tab disables XDMCP, the facility that provides
remote X terminals and sessions the ability to login to your system.
If you have X terminals or additional Linux or Unix hosts, you may
find it convenient to be able to remotely log in to your Red Hat
Linux system. To provide this capability, enable the Enable XDMCP
checkbox. The change takes effect when you close the GDM Setup tool.
Thereafter, X terminals and X sessions on your local network should
be able to remotely log in to your Red Hat Linux system.

If you've enabled XDMCP but are unable to obtain an X login screen, check your firewall settings by using the Security Level Configuration tool. It's likely that your firewall is configured to block remote X access.

If you enable XDMCP, you should generally make a second configuration
change. By default, the Security tab enables the setting Allow root
to login remotely with GDM. Most users do not need to remotely login
as root and therefore don't require this setting to
be enabled. By disabling the setting, you can prevent unauthorized
persons from successfully logging in as root from remote X terminals
or sessions. Therefore, you should generally disable this setting.

9.1.2 Configuring a Printer

Before
you can print from Red Hat Linux, you must configure a printer. Red
Hat Linux supports local printers attached to your
system's parallel port and remote printers that your
system accesses via the network. Before you can configure a remote
printer, you must first configure networking, as explained in Chapter 11.

To configure a local printer, launch the printer configuration tool
by selecting System Tools Printing. The Red Hat
Printer Config Tool, as shown in Figure 9-2,
appears.

Figure 9-2. The printer configuration tool

First, create a new printer by clicking the New icon. The Add a New
Print Queue wizard appears. Click Forward to proceed. The Set the
Print Queue Name and Type dialog box, as shown in Figure 9-3, appears.

Figure 9-3. The Set the Print Queue Name and Type dialog box

Every print
queue has a name. The most commonly used name for the default print
queue is lp. Type lp or another print queue name of your choice
in the text box labeled Queue Name. Select the Local Printer radio
button and click Forward. The Configure a Local Printer dialog box,
as shown in Figure 9-4, appears.

Figure 9-4. The Configure a Local Printer dialog box

The dialog box shows the parallel ports associated with your system.
Linux numbers parallel ports starting with zero, so the port
designated /dev/lp0 corresponds to the device
known by Microsoft Windows as LPT1. Select the parallel port to which
your printer is attached and click Forward.

The
Select a Print Driver dialog box, as shown in Figure 9-5, appears. Select the make of your printer by
clicking the triangle that appears at the left of its name. From the
sublist that appears, select the model of your printer and choose a
print driver, as shown in Figure 9-6. More than one
driver may be available for your printer. Some drivers work better
than others, so you'll eventually want to try each
driver in order to locate the one that works best. For now, merely
choose a driver arbitrarily from among those listed for your printer.
Then click Forward.

Figure 9-5. The Select a Print Driver dialog box

Figure 9-6. The Select a Print Driver dialog box

The Finish and Create the New Print Queue dialog box, as shown in
Figure 9-7, appears. Check the information and use
the Back button to correct any errors. When you're
satisfied with your specifications, click Apply.

Figure 9-7. The Finish and Create the New Print Queue dialog box

The
printer
configuration tool reappears with the new printer, as shown in Figure 9-8. To verify the configuration, click Test and
choose ASCII Text Testpage. Doing so sends a sample page to the
printer so that you can verify correct operation. A dialog box
invites you to save your configuration changes; click Yes, or your
new printer configuration will be lost. The system then restarts the
printer system, known as the
lpd daemon, and informs you of the result by
presenting a dialog box. This process may take several seconds. Click
OK to continue. Finally, a dialog box confirms that the sample page
has been sent to the printer.

Figure 9-8. The printer configuration tool

If the sample page doesn't appear or appears
incorrectly, select the printer and click Edit. Use the Edit Queue
dialog box that appears, as shown in Figure 9-9, to
select a different print driver or revise options associated with the
current driver.

Figure 9-9. The Edit Queue dialog box

9.1.3 Changing the Root User Password

You can change the password
associated with the root user account by using
the Root Password tool. To do so, select System Settings
Root Password. A dialog box, shown in Figure 9-10, appears. Type the desired password twice and
click OK. If the two passwords match, the password is immediately
changed. Otherwise, the tool gives you another opportunity to change
the password.

Figure 9-10. The Root Password tool

The system evaluates passwords and can determine that a password you specify is insecure. In such a case, it may prevent you from using the insecure password or, if you are the root user, it may merely inform you that the password is insecure. Unless your PC is physically secure and never connected to a network, you should choose only secure passwords.

9.1.4 Configuring Sound

If your
system includes a sound adapter supported by Red Hat Linux, you can
use the Sound Card Configuration tool to configure your adapter. If
you're unsure whether your system's
sound adapter is supported, check the Red Hat Linux
hardware compatibility database at
http://hardware.redhat.com.
Several
popular cards are not fully compatible with Red Hat Linux, so
it's best to check the database before wasting time
trying to configure incompatible hardware.

To configure your system's sound adapter, choose
System Settings Soundcard Detection from the GNOME
or KDE menu. The Sound Card Configuration tool appears, as shown in
Figure 9-11.

Figure 9-11. The Sound Card Configuration tool

The tool probes your system, seeking supported sound adapters. After
a sound adapter has been identified, the tool displays the vendor and
model of your sound card and the associated Linux kernel module name.
If the tool was unable to find a sound adapter, it displays the text
"No soundcards were detected."

If your system's sound adapter was sucessfully
probed, you can click the Play test sound button to test the adapter.
If you don't hear the sound, check that your
speakers are plugged in and, if necessary, powered on. Otherwise, you
may spend time trying to reconfigure a sound adapter
that's actually working fine.

If the test sound works, but you don't hear sound at
other times, check the mixer levels by choosing Sound & Video
Volume Control. If you're using
KDE, you should also check Sound& Video Sound
Mixer. You may find that a volume control is set too low or a mixer
setting is preventing you from hearing sounds. Be careful when
adjusting volume and mixer settings. Loud noises can damage
equipment, your hearing, and relationships with neighbors.

To enable desktop sounds, choose Preferences Sound and use the Sound Preferences (GNOME) or Sound Server KDE Control Module (KDE) to configure a sound server to start when the desktop is launched.

9.1.5 User and Group Administration

The Red Hat User Manager tool
lets you administer users and groups. To launch the tool, select
System Settings Users and Groups from the GNOME or
KDE menu. The Red Hat User Manager tool appears, as shown in Figure 9-12. The tool presents a scrollable list of
user accounts
(users) and displays the following information about each user
account:

User Name

The login name associated with the user account.

User ID

The numeric ID associated with the user account. This ID is
automatically assigned when the user account is created and is unique
to each user account.

Primary Group

The name of the primary user group associated with the user account.
Accounts used by people rather than by system processes generally
have an associated primary group having the same name as the user
account.

Full Name

The name of the person or process that owns the user account.

Login Shell

The login shell assigned to the user account. Assigning
/bin/false or /sbin/nologin
prevents the user account from logging in.

Home Directory

The home directory associated with the user account. When the user
logs in, this directory is set as the current working directory.

Figure 9-12. The Red Hat User Manager

When many user accounts are configured, it may be inconvenient to
scroll through the list. You can use the text box labeled Search
Filter to display only user accounts having names matching a
specified pattern. Type the pattern in the text box and click Apply
filter.

9.1.5.1 Modifying a user account

To
modify a user account, click the desired account and click
Properties. The User Properties dialog box, as shown in Figure 9-13, appears.

Figure 9-13. The User Properties dialog box

The User Data pane of the User Properties dialog box lets you view
and change a variety of properties:

User Name

The login name associated with the user account.

Full Name

The name of the person or process that owns the user account.

Password

The password to be associated with the user account.

Confirm Password

The password to be associated with the user account. The password is
specified twice in order to reduce the risk of assigning an incorrect
password due to a typing error.

Home Directory

The home directory associated with the user account. When the user
logs in, this directory is set as the current working directory.

Login Shell

The login shell assigned to the user account. Assigning
/bin/false or /sbin/nologin
prevents the user account from logging in.

The Red Hat User Manager appears to be somewhat buggy. Sometimes, the Red Hat User Manager tool fails to automatically display recent changes. If, after you close the Properties dialog box, your changes aren't seen in the main window, click Refresh. Similarly, sometimes the Properties dialog box cannot be dismissed by clicking OK. In such a close, click the close icon at the top right of the dialog box. Finally, if the tool stubbornly refuses to cooperate, exit and re-launch the tool. Often, this eliminates the problem.

The Account Info pane, shown in Figure 9-14, lets
you specify a date on which a user account becomes unusable.
Alternatively, you can use the text box labeled User account is
locked to immediately disable an account.

Figure 9-14. The Account Info pane of the User Properties dialog box

The Password Info pane, shown in
Figure 9-15, lets you set password expiration
options for the account. To do so, enable the checkbox labeled Enable
password expiration. Then you can specify any of the following
values:

Days before change allowed:

The number of days that must elapse before the user can change the
password associated with the user account.

Days before change required:

After the specified number of days, the user must change the password
associated with the user account.

Days warning before change:

This value is used in combination with the Days Before Change
Required value. The user will be given advance notice of the need to
change the password associated with the user account. The
notification begins the specified number of days before the change
must be made.

Days before account inactive:

After the specified number of days, the user account is disabled.

Figure 9-15. The Password Info pane of the User Properties dialog box

The Groups pane displays a series of checkboxes corresponding to user
groups. To associate the user account with a group, check the box
corresponding to the desired group.

9.1.5.2 Adding a new user

To
create a new user account, click Add User in the Red Hat User Manager
dialog box. This will launch the Create New User dialog box, shown in
Figure 9-16.

Figure 9-16. The Create New User dialog box

When you create a new user account, you can specify the following
values:

User Name

The name of the user account to be created.

Full Name

The name of the user who will use the account.

Password

The password to be associated with the user account.

Confirm Password

Again, the password to be associated with the user account.

Login Shell

The login shell associated with the account. You should generally
select /bin/ bash.

Create home directory

You should generally check this box, so that a home directory is
created.

Home Directory

This value is used only when Create Home Directory is enabled. The
default value is generally acceptable.

Create a private group for this user

You should generally enable this checkbox, which causes automatic
creation of a primary user group having the same name as the user
account.

Specify user ID manually

I recommend leaving this unchecked.

When you've specified the desired values, click OK
to create the user account.

9.1.5.3 Deleting a user account

To
delete a user account, click on the desired account and click Delete.

The user account is immediately deleted; no confirmation dialog box appears. Therefore, exercise care to ensure that the correct user account is highlighted before clicking Delete.

9.1.5.4 Configuring groups

You may
recall from Chapter 4 that Linux uses groups to define a set of
related user accounts that can share access to a file or directory.
You probably won't find it necessary to configure
group definitions very often, particularly if you use your system as
a desktop system rather than a server.

To view the configured groups, launch the User Manager tool and click
the Groups tab. The Groups pane, as shown in Figure 9-17, appears. Groups are shown in a scrollable
list, similar to the way user accounts are shown.

Figure 9-17. The Groups pane of the User Manager

To
create a new group, click the Add Group icon. The Create New Group
dialog box, as shown in Figure 9-18, appears. The
dialog box lets you specify the name of the new group. When
you've specified the name of the new group, click OK
to create the group.

Figure 9-18. The Create New Group dialog box

To modify a group, click on the name of the group. The Group
Properties dialog box, shown in Figure 9-19,
appears. The Group Data pane of the dialog box lets you revise the
name of the group. The Group Users pane contains a scrollable list of
users; you can associate a user account with a group by enabling the
checkbox adjacent to the username or dissociate a user account from a
group by disabling the checkbox adjacent to the username. When
you've completed your changes, click OK to make them
effective.

Figure 9-19. The Group Properties dialog box

To
delete a group, select the group in the Groups pane and click the
Delete icon.

The selected group is immediately deleted. So, before clicking Delete, be sure the proper group is highlighted.

9.1.6 Switching Desktops

During
the installation procedure, GNOME is automatically configured as the
default desktop. You can choose KDE as the default by using the desktop
switcher.To do so, select Extras System Settings
Desktop Switching Tool from the GNOME or KDE menu.
The Desktop Switcher tool, shown in Figure 9-20,
appears.

Figure 9-20. The Desktop Switcher dialog box

In addition to GNOME and KDE, the Desktop Switcher lets you specify
TWM (tiny window manager), a sparsely
functional but highly efficient desktop. The checkbox labeled
"Change only applies to current
display" lets you restrict your choice of desktop to
the current desktop, as indicated in the top line of the dialog box.
This facility is useful if your system has been configured to allow
remote users to log in via X.

To specify a desktop, click the desired radio button and click OK. A
dialog box appears, informing you that you must restart X for the
selected desktop to appear. To restart X, simply log out and then log
in.