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:
Provides access to the Package Management tool, which lets you install and remove RPM packages
Provides access to the Authentication Configuration tool, which lets you configure password settings
Provides access to the Date/Time Properties tool, which lets you configure the time zone, date, and time
Provides access to the Display Settings tool, which lets you configure monitor resolution, color depth, and other display characteristics
Provides access to the Keyboard tool, which lets you choose the keyboard appropriate to your system
Provides access to the Language Selection tool, which lets you choose the current language from among those for which you've installed support
Provides access to the GDM (GNOME Display Manager) Setup tool, which lets you configure how people log in under X
Provides access to the Mouse Configuration tool, which lets you choose the mouse appropriate to your system and enable or disable 3-button emulation
Provides access to the Network Configuration tool, which lets you configure network, modem, virtual private network (VPN), and wireless connections and related settings
Provides access to the Red Hat Printer Configuration tool, which lets you configure printers and control print queues
Provides access to a tool that enables you to change the root password
Provides access to the Security Level Configuration tool, which lets you configure a firewall to protect your system from network attacks
Provides access to the Sound Card Detection tool, which configures, and enables you to verify the operation of, your sound card
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 System Setings menu contains a More System Settings submenu, on which you can find one more tool: the Desktop Switching Tool, which lets you choose between the GNOME and KDE desktop if you've installed both desktops. You may also find a Server Settings submenu, which you can use to configure servers you've installed. This chapter explains how to control services. Chapter 12 explains how to install and configure commonly used servers.
Most of the System Settings tools function much like the Red Hat Linux installation procedure. This section focuses on tools that do not resemble installation procedure steps, namely:
GDM Setup tool, accessed via the Login Screen menu item
Red Hat Printer Configuration 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.
The GDM Setup tool, accessible via System Settings Login Screen from the main 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- or 24-hour format. However, the Security and XDMCP tabs provide options that you should consider changing.
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 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 system.
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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.
Before you can print, you must configure a printer. Red Hat Enterprise Linux and Fedora Core support 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.
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To configure a local printer, launch the printer configuration tool by selecting System Settings Printing from the main menu. The Red Hat printer configuration tool (Figure 9-2) appears.
First, create a new printer by clicking the New icon. The Add a New Print Queue wizard appears. Click Forward to proceed. The "Queue name" dialog box (Figure 9-3) appears.
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 Name and click Forward.
The "Queue type" dialog box (Figure 9-4) appears.
This 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 default queue type, Locally-connected. Then, select the device to which the locally connected printer is attached and click Forward. If the appropriate device does not initially appear, you may be able to use the Rescan Devices button to cause it to appear. Alternatively, you can use the Custom device button to launch a dialog box that enables you to manually specify the device. Click Forward.
The "Printer model" dialog box (Figure 9-5) appears. Select the make of your printer by clicking the caret that appears at the right of the listbox labeled Select the printer manufacturer and model. From the sublist that appears, select the model of your printer. Then click Forward.
The "Finish, and create the new print queue" dialog box (Figure 9-6) appears. Check the information and use the Back button to correct any errors. When you're satisfied with your specifications, click Apply.
A message box appears, asking if you'd like to print a test page. In order to verify that your printer is operational, you should generally click Yes. Doing so sends a sample page to the printer. After a few seconds, another message box should inform you that the test page has been printed. When you dismiss the message box, the printer configuration tool (Figure 9-7) appears.
If the test page was actually printed, you know that the printing facility is operational. Otherwise, you should check the printer status and cables. If the sample page still doesn't appear or appears incorrectly, select the printer and click Edit. Use the "Edit a print queue" dialog box that appears (Figure 9-8) to select a different print driver or revise options associated with the current driver.
When you exit the printer configuration tool, you're prompted to save your configuration changes. If you choose not to do so, recent changes are discarded.
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 from the main menu. A dialog box (Figure 9-9) 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.
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If your system includes a compatible sound adapter, you can use the Soundcard Detection tool to automatically configure your adapter. If you're unsure whether your system's sound adapter is supported, check the Red Hat Enterprise Linux hardware compatibility database at http://hardware.redhat.com. Several popular cards are not fully compatible with Red Hat Enterprise Linux, so it's best to check the database before wasting time trying to configure incompatible hardware.
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To configure your system's sound adapter, choose System Settings Soundcard Detection from the main menu. The Audio Devices dialog box (Figure 9-10) appears.
The soundcard detection 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 successfully 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 from the main menu. If you're using KDE, you should also check Control Center Sound & Video Sound System 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.
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The Red Hat User Manager tool lets you administer users and groups. To launch the tool, select System Settings Users and Groups from the main menu. The Red Hat User Manager tool (Figure 9-11)appears.
The tool presents a scrollable list of user accounts (users) and displays the following information about each user account:
The login name associated with the user account.
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.
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.
The name of the person or process that owns the user account.
The login shell assigned to the user account. Assigning /bin/false or /sbin/nologin prevents the user account from logging in.
The home directory associated with the user account. When the user logs in, this directory is set as the current working directory.
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.
To modify a user account, click the desired account and click Properties. The User Properties dialog box (Figure 9-12) appears.
The User Data pane of the User Properties dialog box lets you view and change a variety of properties:
The login name associated with the user account.
The name of the person or process that owns the user account.
The password to be associated with the user account.
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.
The home directory associated with the user account. When the user logs in, this directory is set as the current working directory.
The login shell assigned to the user account. Assigning /bin/false or /sbin/nologin prevents the user account from logging in.
The Account Info pane (Figure 9-13) lets you specify a date on which a user account becomes unusable. Alternatively, you can use the text box labeled "Local password is locked" to immediately disable an account.
The Password Info pane (Figure 9-14) lets you set password expiration options for the account. To do so, enable the checkbox labeled Enable password expiration.
Choosing a Secure PasswordA cracker who manages to obtain a copy of your system's /etc/shadow file may be able to discover your password by using a utility that tries to determine your password by decrypting the encrypted password stored in the file. You can make the cracker's job more difficult by using one or more of the following techniques:
Other things being equal, the longer a password is used, the greater the likelihood that it has been compromised. One way to protect users from password crackers is to require users to change their passwords regularly. Some overly zealous system administrators require users to change their passwords every 30 days. Unless a system contains top secret data, such a short interval is unnecessary, amounting to what's called password fascism. You may find that requiring users to change their passwords every six months or every year is sufficient to avoid hacker invasion of user accounts. |
Then you can specify any of the following values:
The number of days that must elapse before the user can change the password associated with the user account.
After the specified number of days, the user must change the password associated with the user account.
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.
After the specified number of days, the user account is disabled.
The Groups pane displays a series of checkboxes corresponding to existing user groups. To associate the user account with a group, check the box corresponding to the desired group.
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 (Figure 9-15).
When you create a new user account, you can specify the following values:
The name of the user account to be created.
The name of the user who will use the account.
The password to be associated with the user account.
Again, the password to be associated with the user account.
The login shell associated with the account. You should generally select /bin/ bash.
You should generally check this box, so that a home directory is created.
This value is used only when Create Home Directory is enabled. The default value, which creates a home directory named after the user, is generally acceptable.
You should generally enable this checkbox, which causes automatic creation of a primary user group having the same name as the user account.
Leave this box unchecked unless you want to manually specify the numeric ID associated with the user account. You won't generally need to enable this option.
When you've specified the desired values, click OK to create the user account.
To delete a user account, click on the desired account and click Delete. A message box asks you to confirm your decision to delete the account. The message box also enables you to specify whether the home directory associated with the user account should be deleted.
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 (Figure 9-16) appears. Groups are shown in a scrollable list, similar to the way user accounts are displayed.
To create a new group, click the Add Group icon. The Create New Group dialog box (Figure 9-17) appears. The dialog box lets you specify the name of the new group. It also lets you manually specify the numeric ID of the group; however you should rarely need to do so. When you've specified the name of the new group, click OK to create the group.
To modify a group, click on the name of the group. The Group Properties dialog box (Figure 9-18) 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.
To delete a group, select the group in the Groups pane and click the Delete icon. A message box asks you to confirm your decision to delete the group.
During the installation procedure, GNOME is automatically configured as the default desktop. If you installed KDE, you can choose KDE as the default by using the desktop switcher. To do so, select System Settings More System Settings Desktop Switching Tool from the main menu. The Desktop Switcher tool (Figure 9-19) appears.
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 display (generally localhost.localdomain:0.0), 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.