The Netstat tab provides information on three sets of network data available on the workstation:

• The routing table
• The active network services
• The multicast network information

Ubuntu maintains an internal routing table to keep track of how to forward network packets to remote networks. Selecting the Routing Table radio button then clicking the Netstat button produces a list.

The routing table matches network destinations with a gateway that can send the packets to the remote network. The routing table always includes at least two entries. One entry is the default route, 0.0.0.0. This route defines the gateway to use by default for sending packets to any network on the Internet. Usually this gateway is the IP address of your broadband modem connection.

The other route defines the local network your Ubuntu workstation is connected to. In the example, the workstation is connected to the 10.0.1.0 public network address and uses the default gateway to send packets to this network.

The active network services selection displays a list of what network ports are currently in use on the workstation. Different software packages use different network ports to listen for incoming connections. Many network servers are assigned standard network ports, such as TCP port 80 for web servers and TCP port 25 for email servers.

The network port list includes the current state of the port. TCP uses 11 states to define what mode the network port is in.


TCP Network Port States
LISTEN Waiting for a connection request from a remote client

SYN-SENT Sent a connection acknowledgment and waiting for one in return

SYN-RECEIVED Received a connection acknowledgment from remote client

ESTABLISHED Port is ready to send and receive data with the remote client

FIN-WAIT-1 Sent a connection disconnect request to the remote client

FIN-WAIT-2 Received a connection disconnect from the remote client in response to a connection disconnect request sent by the port

CLOSE-WAIT Remote client initiated a connection disconnect

CLOSING Waiting for a response from a sent connection disconnect request

LAST-ACK Waiting for remote client to acknowledge a connection disconnect request

TIME-WAIT The port is on hold for a preset amount of time after the connection disconnects

CLOSED The connection is officially closed



The TCP states are invaluable for troubleshooting network programs. By checking the network port states, you often can determine whether a remote device is closing a connection early or is keeping a connection open too long.

The final feature of the Netstat tab is the multicast network information. This protocol allows devices to subscribe to special multicast IP addresses on network routers. Network routers handle multicast packets only when they have a device on the network that requests them. This list displays whether the Ubuntu workstation has registered to receive any multicast packets on the network.

Source of Information : Wiley Ubuntu Linux Secrets

If you use a dial-up modem to access the Internet, you’ll have to do some manual configuration to tell Ubuntu how to contact your ISP. This is done using the GNOME PPP application. You’ll first have to manually install the GNOME PPP application using the Synaptic Package Manager before you can use it to connect to your ISP.

Just start Synaptic, search for the GNOME PPP package, mark it for installation, then apply the changes. After installing the GNOME PPP package, follow these steps to configure a PPP session to connect to your ISP:

1. Start the GNOME PPP dialog box by selecting Applications -> Internet -> GNOME PPP from the Panel menu. The main GNOME PPP dialog box.

2. Click the Setup button at the bottom of the dialog box. This opens the Setup dialog box, where you can configure you modem settings.

3. Configure your modem settings in the Modem tab. You must select which port your modem uses to communicate. If Ubuntu automatically detects your modem, it assigns it to the special port /dev/modem. If that doesn’t work, Ubuntu uses /dev/ttyS0 for COM1, /dev/ttyS1 for COM2, and so on.

4. Click the Networking tab to set your IP address information. If your ISP dynamically assigns an IP address to your workstation, select the Dynamic IP Address radio button. If you must specify a static IP address, select the Static IP Address radio button and enter your IP address information in the text boxes. If your ISP uses a static address, you’ll also need to configure the DNS server to use for the network.

5. Click the Options tab to set additional features for the modem connection. You can set the Modem Connection icon to minimize when the connection is established or dock itself on the panel. You can also choose advanced connection features from this page, such as having the modem reconnect if the connection drops.

6. Click the OK button to save the settings.

7. Back in the main GNOME PPP dialog box, enter the information needed to contact your ISP account. You must provide the phone number, plus any special prefixes (such as a 9 to get an outside line). Enter the userID and password provided by your ISP and select the check box if you want GNOME PPP to remember your password.

8. Click the Connect button to initiate the connection to the ISP.

Once you’ve activated your dial-up modem, Ubuntu will attempt to use it to access the Internet via your ISP whenever a network request is made.

Source of Information : Wiley Ubuntu Linux Secrets

These days it seems that everything is going wireless, from ordinary household appliances to gadgets you hook to your cell phone. The computer world is no different. Wireless network connections are becoming more popular as home users search for an easier way to connect multiple computers to a broadband Internet connection.

There are three current standards and one proposed standard in the wireless network card world:

• 802.11a: Provides up to 54 Mbps of data connectivity but has only a 35-meter range.

• 802.11b: Provides only up to 11 Mbps but has a larger range than the 802.11a specification.

• 802.11g: Provides up to 54 Mbps and has a larger range than the 802.11b specification.

• 802.11n (proposed): Provides up to 248 Mbps, with a range of up to 70 meters.


The benefits of the new 802.11n wireless have made it a commercial success, even before
its formal adoption as a network standard. The downside to wireless network cards is that many of them don’t provide drivers for Linux. Ubuntu can detect and use many wireless network cards, but not all of them.


Besides the network type, you also must worry about whether the wireless network is protected by a security system. Wireless networks offer several types of encryption schemes to protect them from unwanted visitors. The most popular encryption schemes used are

• WEP: The wired equivalent privacy protocol is the oldest and least secure encryption scheme. It uses RC4 encryption with either a 64- or 128-bit key. The key is usually entered as a series of hexadecimal digits, often as text characters, to create a password.

• WPA: The Wi-Fi protected access protocol uses the RC4 encryption scheme with a 128-bit key but dynamically changes the key as the system is used. It can be used with a server that provides separate keys to each device on the network or, for less secure environments, it can provide a pre-shared key (PSK) mode in which multiple computers on the network can share the same key.

• WPA2: The second version of the Wi-Fi protected access protocol uses a more secure advanced encryption standard (AES)-based scheme that for now is considered fully secure and not breakable.

You must know the encryption type as well as the password to connect to a wireless network that uses a security scheme. If you happen to find a network that’s not encrypted, Network Manager will automatically connect you.

Source of Information : Wiley Ubuntu Linux Secrets

The DSL modem uses normal telephone lines to communicate to the ISP. However, instead of converting the digital signal to analog, the DSL modem sends a digital signal directly across the telephone line. The telephone line carries both the analog voice signal and the digital signal on the same wires to the telephone provider, which in turn must separate the two signals, connecting the digital signal to its servers and the analog signal to the appropriate telephone exchange equipment.

Your telephone provider must have the proper equipment installed to be able to provide DSL service to your location. Not all areas are converted to support DSL connectivity. Check with your telephone provider to determine whether they support DSL modems in your area.

Three basic types of digital modems can be used on a digital telephone line:

Integrated services digital network (ISDN): The ISDN modem is the oldest technology and is the most sensitive to distance. It offers up to 128 kbps of connectivity speed (more than double the speed of a dial-up modem), provided that the end connection is within 3.4 miles of the telephone exchange equipment. Performance degrades the farther away you are from the telephone exchange, which is one reason why ISDN didn’t catch on all that well.

Symmetric digital subscriber line (SDSL): SDSL provides a constant upload and download speed using the entire bandwidth provided on the telephone line, so it’s not able to share the same line with an analog signal. SDSL lines can provide up to 2,320 kbps of upload and download speeds.

Asymmetric digital subscriber line (ADSL): ADSL provides a constant upload and download speed but can share the same telephone line with an analog signal, allowing an ADSL modem and a telephone to operate at the same time on the single telephone line. ADSL splits the upload and download speeds, so they don’t have to be the same. This method allows much faster download speeds but at the expense of the upload speeds. ADSL lines can provide download speeds up to 24 megabits per second (Mbps) but usually limit upload speeds to no more than 3.5 Mbps. A typical home ADSL installation provides 8 Mbps of download speed and 1 Mbps of upload speed. For the average home user who downloads videos, music, and Linux distribution ISO files, ADSL is a perfect solution.

The second and third categories of digital modem Internet access is referred to as xDSL. Most xDSL providers distribute a simple DSL modem, which you install by simply plugging it into your normal telephone jack to connect to the telephone company. The DSL modem is usually set to communicate automatically with the telephone system’s ISP.

The DSL modem uses Ethernet to communicate with the workstation. The Ethernet protocol has been a communications standard for decades and is supported by various types of media. The two most popular methods for communicating via Ethernet today are
• Wired Ethernet network cards
• Wireless Ethernet cards

Source of Information : Wiley Ubuntu Linux Secrets

Installing Packages
Installing software packages using Synaptic is a breeze. Just follow these steps to install a new package:
1. Open Synaptic by selecting System -> Administration -> Synaptic Package Manager from the Panel menu.

2. Enter your password in the Password dialog box prompt. The Synaptic Package Manager requires administrative permissions to install and remove software packages. If your user account doesn’t have administrative permissions, you won’t be able to use the program.

3. Enter the package name in the Quick Search box. The Search tool searches all of the configured repositories, looking for packages that contain the search word in the name and description, then displays packages that match in the package list, displays the results of a search for the SuperTux game. If you require a more detailed search, use the Search button on the toolbar and select different search criteria.

4. Click the SuperTux package and select the Mark for Installation option from the menu. Synaptic automatically locates any dependent packages required by the selected packages and asks whether you want to mark those for installation as well. Packages marked for installation appear with an error in the status box and are highlighted in green if all of the dependency packages are available.

5. Click the Apply button in the toolbar. The Synaptic installation process begins, downloading and installing the selected packages.

6. Synaptic asks whether you want to install more packages. If you’re done, select No.


Once the packages are installed you may or may not see them in the Ubuntu menu system, depending on what type of packages they are. Some packages require opening a Terminal session and starting them from the command line. You can manually create a menu entry for these packages.


Removing Packages
When you view the package list in Synaptic, installed packages have a green status box, indicating that all of the components for that package are installed. Right-clicking on the package produces a menu that gives you three options for managing the installed package:
• Mark for Reinstallation: Reinstall the package from the current version in the repository.
• Mark for Removal: Remove only the files installed by the package.
• Mark for Complete Removal: Remove the package files plus any additional configuration or data files associated with the application.

If you want to reinstall the package but have customized configuration files you’d like to use with the reinstallation, select Mark for Removal rather than Mark for Complete Removal. A complete removal will delete any custom configuration you’ve done to the package.


Once the packages are installed you may or may not see them in the Ubuntu menu system, depending on what type of packages they are. Some packages require opening a Terminal session and starting them from the command line. You can manually create a menu entry for these packages.

Source of Information : Wiley Ubuntu Linux Secrets

Start the Synaptic Package Manager by selecting System -> Administration -> Synaptic Package Manager. After you enter your password, the main Synaptic Package Manager window appears.

The main window is divided into six sections:
• The menu bar
• The toolbar
• The category selector
• The package list
• The description field
• The status bar
Each of these sections provides features for managing the packages on the system, as described in the following sections.


The Menu Bar
The menu bar provides access to all of the features in Synaptic, separated into standard menu categories:

• File: Provides features for saving selected package settings and restoring them from a file, generating a script to perform the selected package installations at a later time, adding downloaded packages, and displaying the history of package operations.

• Edit: Lets you undo a change, unmark all selections to start over, search for a specific package, reload package information from repositories, add a local CD to the repository list, mark all packages that have available upgrades, and fix broken packages.

• Package: Controls package management, such as marking packages for installation, reinstallation, upgrade, or removal; locking a package version; forcing a specific version of a package; and configuring a package.

• Settings: Allows you to configure repositories (the Software Sources window), preferences, and filters used for determining which packages are available.

• Help: Provides quick access to the Synaptic Package Manager manual, as well as access to online help, if available.


In the Preferences window you can specify how Synaptic handles package changes, displays package information, and connects to the remote software repositories (if a network proxy server is required). You can also specify whether to load only the package versions that match the current distribution release.

By default, Ubuntu allows you to install the highest-available version of a software package. Sometimes, though, this can cause problems when working with other packages in the distribution. If you need to synchronize all of the packages in your distribution to the same release levels, click the Distribution tab in the Preferences window and select the Always Prefer the Installed Version option.


The Toolbar
The toolbar provides quick access to common functions in Synaptic:
• Reload: Refresh the package list from the configured repositories
• Mark All Upgrades: Mark all installed packages that have an upgrade available.
• Apply: Perform the operations as marked in the package list.
• Properties: Display the properties for the selected package.
• Quick Search: Enter text in the text box to perform a real-time search of the package based on package names and descriptions.
• Search: Search for packages using other attributes, such as version numbers, dependencies, and the maintainer. Although there aren’t many buttons in the Synaptic toolbar, the ones supplied should cover most of the features you need for normal operations.


The Category List
The category list helps filter the packages that appear in the package list. There are five categories of filters you can select from:
• Sections: Contains individual section filters based on the package application type.
• Status: Displays the status of the package—installed or not installed.
• Origin: Filters packages based on which repository they were loaded from.
• Custom Filters: Lets you create your own definitions for filtering packages.
• Search Results: Filters the results based on the Search tool.

The Sections filter divides packages into sections based on the primary category they belong to. There are 32 different categories of packages, such as base packages loaded at installation time, GNOME packages, KDE packages, networking packages, and library packages. Within each category there may be multiple entries, depending on the type of applications:
• Main: open-source packages supported by Ubuntu
• Multiverse: packages that may be covered by copyright or patent licensing but are not supported by Ubuntu and are not provided with automatic updates
• Restricted: packages that are supported by Ubuntu but are not open-source programs, such as proprietary hardware drivers
• Universe: packages that are open-source and supported by the open-source community but are not supported directly by Ubuntu (Ubuntu doesn’t guarantee updates for these packages but may provide them if they are available) Packages not marked as one of these four types are part of the Ubuntu main repository and are fully supported by Ubuntu.


The Package List
The package list displays the packages available on the system, depending on the filters set in the category list. The package list provides five pieces of information about the packages:
• The package status (installed, not installed, marked for upgrade, marked for installation, or marked for removal)
• The package name
• The installed version of the package
• The version currently available in the repository
• A brief description of the package

When you select a package, the lower section of the package list provides a more detailed description of the package.

Source of Information : Wiley Ubuntu Linux Secrets