Lowe D. Networking For Dummies

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Book IX

Chapter 2

Getting Used

to Linux

687

Linux: It Isn’t Windows

The fundamental difference between the Linux and Windows file system is

that Linux treats everything in the entire system as a file, and it organizes

everything into one gigantic tree that begins at a single root. When I say,

“Everything is treated as a file,” I mean that hardware devices such as floppy

drives, serial ports, and Ethernet adapters are treated as files.

The root of the Linux file system is the root partition from which the operat-

ing system boots. Additional partitions, including other devices that support

file systems such as CD-ROM drives, floppy drives, or drives accessed over

the network, can be grafted into the tree as directories called mount points.

Thus, a directory in the Linux file system may actually be a separate hard

drive.

Another important aspect of the Linux file system is that the directories that

compose a Linux system are governed by a standard called the Filesystem

Hierarchy Standard (FHS). This standard spells out which directories a Linux

file system should have. Because most Linux systems conform to this stan-

dard, you can trust that key files will always be found in the same place.

Table 2-1 lists the top-level directories that are described in the FHS.

Table 2-1 Top-Level Directories in a Linux File System

Directory Description

/bin

Essential command binaries

/boot

Static files of the boot loader

/dev

Devices

/etc

Configuration files for the local computer

/home

Home directories for users

/lib

Shared libraries and kernel modules

/mnt

Mount point for file systems mounted temporarily

/opt

Add-on applications and packages

/root

Home directory for the root user

/sbin

Essential system binaries

/tmp

Temporary files

/usr

Read-only, shared files such as binaries for user commands and

libraries

/var

Variable data files

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688

On Again, Off Again

Any user who accesses a Linux system, whether locally or over a network,

must be authenticated by a valid user account on the system. In the follow-

ing sections, you find out how to log on and off of a Linux system and how to

shut down the system.

Logging on

When Linux boots up, it displays a series of startup messages as it starts the

various services that compose a working Linux system. Assuming that you

selected X Window when you installed Linux, you’re eventually greeted by

the screen shown in Figure 2-1. To log on to Linux, type your user ID on this

screen, press Enter, and then type your password and press Enter again.

(Note that this logon screen is for Fedora. Other distributions have similar

logon screens.)

Figure 2-1:

Logging on.

As a part of the installation process, the Setup Agent created a user account

for you. You should use this user account rather than the root user account

whenever possible. Use the root account only when you are making major

changes to the system’s configuration. When you’re doing routine work,

log on as an ordinary user in order to avoid accidentally corrupting your

system.

When you log on, Linux grinds its gears for a moment and then displays the

GNOME desktop, which I describe later in this chapter.

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Using GNOME

Logging off

After you’ve logged on, you’ll probably want to know how to log off. To do

so, choose System➪Log Out. A dialog box asks whether you’re sure that you

want to log out. Click Log Out.

Shutting down

As with any operating system, you should never turn off the power to a

Linux server without first properly shutting down the system. You can shut

down a Linux system by using one of these two techniques:

✦ Press Ctrl+Alt+Delete.

✦ Choose System➪Shut Down.

Using GNOME

Figure 2-2 shows a typical GNOME desktop with the Text Editor application

open. As you can see, the GNOME desktop looks a lot like Microsoft Windows.

In fact, many of the basic skills used for working with Microsoft Windows — such

as moving or resizing windows, minimizing or maximizing windows, and using

drag-and-drop to move items between windows — are almost exactly the

same in GNOME. So you should feel right at home.

Figure 2-2:

The

desktop.

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Getting to a Command Shell

The following paragraphs describe some of the key features of the GNOME

desktop:

✦ On the desktop, you can find several icons that let you access common

features. The Home icon lets you access your home directory. The

Computer icon is similar to the My Computer icon in Windows. And the

Trash icon is similar to the Recycle Bin in Windows.

✦ The panel at the top of the desktop area includes several menus and

icons. The Applications menu lists applications you can run, and the

Actions menu lists actions you can perform.

✦ Workspaces, you ask? A workspace is like a separate desktop where

you can keep windows open in order to reduce the clutter on your

screen. The panel beneath the desktop area contains a tool called the

Workspace Switcher, which lets you switch active workspaces by clicking

one of the rectangles in the grid.

Getting to a Command Shell

You can get to a command shell in one of two basic ways when you need to

run Linux commands directly. The first is to press Ctrl+Alt+Fx to switch to

one of the virtual consoles. (If you aren’t sure which function key to use to

open a virtual console, take a look back at the “Virtual consoles” section in

this chapter.) Then, you can log on and run commands to your heart’s con-

tent. When you’re done, press Ctrl+Alt+F7 to return to GNOME.

Alternatively, you can open a command shell directly in GNOME by choos-

ing Applications➪System Tools➪Terminal. This opens a command shell in

a window right on the GNOME desktop, as shown in Figure 2-3. Because this

shell runs within the user account that GNOME is logged on as, you don’t

have to log on. You can just start typing commands. When you’re done, type

Exit to close the window.

Figure 2-3:

A terminal

window.

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Managing User Accounts

One of the most common network administration tasks is adding a user

account. The Setup Agent prompts you to create a user account the first

time you start Linux after installing it. However, you’ll probably need to

create additional accounts.

Each Linux user account has the following information associated with it:

✦ Username: The name the user types to log on to the Linux system.

✦ Full name: The user’s full name.

✦ Home directory: The directory that the user is placed in when he or she

logs on. In Fedora, the default home directory is /home/username. For

example, if the username is blowe, the home directory will be /home/

blowe.

✦ Shell: The program used to process Linux commands. Several shell

programs are available. In most distributions, the default shell is /bin/

bash.

✦ Group: You can create group accounts, which make it easy to apply

identical access rights to groups of users.

✦ User ID: The internal identifier for the user.

You can add a new user by using the useradd command. For example,

to create a user account named slowe, using default values for the other

account information, open a Terminal window or switch to a virtual console

and type this command:

# useradd slowe

The useradd command has many optional parameters that you can use to

set account information, such as the user’s home directory and shell.

Fortunately, most Linux distributions come with special programs that sim-

plify routine system management tasks. Fedora is no exception. It comes

with a program called User Manager, shown in Figure 2-4. To start this pro-

gram, choose System➪Administration➪User and Groups.

To create a user with User Manager, click the Add User button. This brings

up a dialog box that asks for the user’s name, password, and other informa-

tion. Fill out this dialog box and then click OK.

The User Manager also lets you create groups. You can simplify the task of

administering users by applying access rights to groups rather than indi-

vidual users. Then, when a user needs access to a resource, you can add the

user to the group that has the needed access.

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Managing User Accounts

Figure 2-4:

Managing

users and

groups.

To create a group, click the Add Group button. A dialog box appears, asking

for the name of the new group. Type the name you want and then click OK.

To add a user to a group, click the Groups tab in the User Manager. Then,

double-click the group to which you want to add users. This brings up the

Group Properties dialog box. Click the Group Users tab and then select the

users that you want to belong to the group.

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Chapter 3: Basic Linux Network

Configuration

In This Chapter

✓ Configuring network interfaces

✓ Looking directly at network configuration files

✓ Using the ifconfig command to display network status

n many cases, configuring a Linux server for networking is a snap. When

you install Linux, the installation program automatically detects your net-

work adapters and installs the appropriate drivers. Then, you’re prompted

for basic network configuration information, such as the computer’s IP

address, host name, and so on.

However, you may need to manually change your network settings after

installation. You may also need to configure advanced networking features

that aren’t configured during installation. In this chapter, you discover the

basic procedures for configuring Linux networking services.

Using the Network Configuration Program

Before you can use a network interface to access a network, you have to

configure the interface’s basic TCP/IP options, such as its IP address, host

name, Domain Name System (DNS) servers, and so on. In this section, I show

you how to do that by using Fedora’s Network Configuration program. You

can access this program by choosing System➪Administration➪Network.

If you prefer a more masochistic approach to configuring your network, see

the section “Working with Network Configuration Files,” later in this chapter.

The Network Configuration program lets you configure the basic TCP/IP

settings for a network interface by pointing and clicking your way through

tabbed windows. Here are the steps:

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Using the Network Configuration Program

1. Choose System➪Administration➪Network.

The Network Device Control window appears, as shown in Figure 3-1.

Figure 3-1:

The

Network

Device

Control

program.

2. Click Configure.

This summons the Network Configuration window, shown in Figure 3-2.

Figure 3-2:

The

Network

Config-

uration

program.

3. Select the adapter that you want to configure and then click Edit.

The main window of the Network Configuration lists all the network inter-

faces installed in your computer. If your computer has more than one

interface, make sure that you select the correct one before proceeding.

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Network

Configuration

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Using the Network Configuration Program

When you click Edit, the Ethernet Device window appears, as shown in

Figure 3-3.

4. To configure the device to use DHCP, select the Automatically Obtain

IP Address Settings with DHCP radio button, type the computer’s

name in the Hostname text box, and select the Automatically Obtain

DNS Information from Provider option.

If you plan on setting up this computer to be your network’s DHCP or

DNS server, you shouldn’t select this check box. Instead, you should

assign a static IP address as described in Step 5.

Some DHCP servers can’t provide DNS information. In that case, you

shouldn’t select the Automatically Obtain DNS Information from

Provider option. Instead, you should manually configure your DNS infor-

mation, as described in Steps 7 and 8.

5. To configure the device with a static IP address, select the Statically

Set IP Addresses option and then enter the IP address, subnet mask,

and Default Gateway that you want the adapter to use.

The IP address is most likely located on one of the standard private

subnets. You should almost always use a private address in the form

192.168.x.x.

Figure 3-3:

Configure

basic TCP/

IP settings

in the

Ethernet

Device

window.

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Using the Network Configuration Program

If you’re setting up this computer to be the gateway router that will

manage traffic between your local network and the Internet, use a static

address that is easy to remember, such as 192.168.1.1.

The subnet mask should be the mask that’s appropriate for the IP

address you choose. For a 192.168.x.x address, use 255.255.255.0.

The default gateway address should be the address of the gateway

router that links your network to the Internet. If this computer is the

gateway router, specify the gateway address provided to you by your

Internet service provider (ISP).

6. Click OK.

You’re returned to the Network Configuration window.

7. Click the DNS tab.

The DNS configuration settings appear, as shown in Figure 3-4.

Figure 3-4:

Configuring

DNS

settings.

8. Enter the IP addresses for the DNS servers that you want to use.

If your network runs its own DNS server, you can specify its address

here. Otherwise, you have to get the DNS server addresses from your

ISP.

9. Choose File➪Save.

Any changes that you’ve made to the network configuration are saved.

Then, an informative dialog box appears with the following message:

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