Live CDs

   If you've not come across Live CDs, you might be a bit unsure as to what they are. Basically, a Live CD is a single CD that enables you to boot into a fully functional operating system, in this case Fedora. The Live CD stores all the system files on the CD in a compressed format, uncompressing parts of the operating system as needed. The upshot of this is that you can give Fedora a try without having to repartition or otherwise modify your hard drive.
   More important, however, the Live CD enables you to test your hardware to make sure that it is compatible with Fedora. When you are happy, you can use the Live CD to give you a base Fedora installation. Just double-click the Install icon on the desktop and follow the installation instructions found later in this chapter. For now, download and burn the Live CD ISO file to a blank CD using your favorite CD-burning application — it will come in handy later!

What Is a Partition?

   It can be difficult to explain to new users about partitions. A useful analogy is of a kitchen, in which there are many different drawers and cupboards. Imagine the kitchen is your hard drive, and the drawers and cupboards are partitions. In one cupboard, you may keep cups, another might hold ingredients, yet another may hold pots and pans. They are all part of the kitchen but have specific roles within the kitchen.
   Taking this back to your hard drive, you may have a partition to hold your user information, another partition to hold the files you will use for serving web pages, and another for boot information.

DVD Installation Jump-Start

   To install Fedora from the DVD included with this book, you must have at least a Pentium-class CPU, 800MB hard drive, and 128MB RAM. You need at least 192MB to install with Fedora's graphical installer. A 10GB hard drive can easily host the entire distribution, leaving about 3GB free for other data. Most modern systems have significantly larger drives, but it is still a good idea to invest in more storage from your local computer store.
   To begin the installation, you need to get into your computer's BIOS to set the boot sequence so that the CD/DVD drive is the first drive that is booted. Insert the DVD into the drive and let the system boot. When the boot: prompt appears, press the Enter key and follow through the various dialog boxes to install Fedora.
   Make sure that you make a note (mental or otherwise) of the root password because you will need it later. When the installer is finished, the DVD ejects and you are asked to reboot the computer. A few more dialog boxes appear to allow you to do some more initial configuration of the system before you are greeted with a login prompt. Make sure to log in as the user you created during the installation and not as root. Finally, finish the install, remove the DVD from your computer, and reboot. Then log in and enjoy Fedora!

TIP

   Just press Enter at the boot prompt if you boot to a network install by using a CD-R created with the boot.iso image. You will boot a graphical network install.

NOTE

   See Chapter 20 for details on how to configure the vsftpd FTP server. Chapter 17 provides information on how to set up and configure Apache for web service. See Chapter 19, "File and Print," for Samba settings. Note that you can have your server perform all three duties.

NOTE

   If you are using the Live CD, we assume that you have double-clicked the Install icon on the desktop. Pick up the instructions below at the Release Notes point.

CAUTION

   If you are wanting to dual boot with Windows, make sure you have prepared your partitions, using the instructions detailed earlier.

TIP

   If you are installing to a system that has an older display monitor, it is a good idea to have your monitor's manual handy during the installation. If the install does not detect your monitor settings, you might need to specify the monitor's vertical and horizontal frequencies. This does not happen often, but if it does, you will be prepared.

TIP

   The installer starts automatically in 60 seconds. Press the spacebar, reboot, or turn off your PC if you need to halt the install.

NOTE

   Fedora's installer supports the capability to monitor background and install processes running during an installation. You can watch the progress of an install and hardware information reported by the Linux install kernel by navigating to a different console display or virtual console. To do so, simultaneously press the Ctrl, Alt, and the appropriate function key (such as F1-F5).
   Use this approach to watch for kernel messages, monitor hardware detection, gain access to a single-user shell, and view the progress of the installer script.
   When using a graphical installer, press Ctrl+Alt+F4 (then Alt+F2 or Alt+F3) to navigate to the various screens. Press Alt+F7 to jump back to the installer. When performing a text-based installation, use Alt+F2 (then Alt+F3 or Alt+F4). Use Alt+F1 to jump back to a text-based install.

NOTE

   If you followed the earlier partitioning instructions, choose to Use Free Space on Selected Drives and Create Default Layout.

Logical Volume Management for Beginners

   Logical volume management sounds a lot more difficult than it is. In effect, what it does is allow you to produce single logical partitions that can be made up of multiple physical drives. Logical volumes can also be resized as required, something that is usually difficult when dealing with ext3 partitions (Fedora's native partition type). There is one thing that you need to remember: Create a separate /boot partition independent of the logical volumes; otherwise, your system will not boot!

TIP

   Fedora works well with other operating systems, but the reverse is not always true. If you need specialized help with configuring a dual-boot system, check various HOWTOs at http://www.tldp.org for hints and tips.

NOTE

   If you are planning to dual boot your PC with Windows, it appears in the list of boot options as Other. You can click the Edit button to access options that enable you to rename it something a little more informative, or even set Windows as the default option for GRUB.

NOTE

   If the Linux kernel finds more than one network interface installed on your computer, you might be asked to configure a second ethernet device. This might be the case, for example, if you are installing Fedora on a computer that serves as a gateway or fire wall. If you configure more than one ethernet device, the device named eth0 is the first active interface when you start Fedora.

TIP

   Read the man page for the hwclock command to learn how to keep a running Linux system synchronized with a PC's hardware clock.

CAUTION

   Do not forget your system's BIOS, boot loader, or root passwords! Some equipment, such as notebook computers, might require factory replacement of motherboard components if the owner forgets the BIOS password. The BIOS settings on most desktop PCs can usually be reset via a jumper or removal and insertion of the motherboard battery. If you forget your boot loader password, use a boot disk (perhaps created during installation as shown later on in this chapter) or boot to a rescue mode by using your Fedora disc and reset the root password, using the passwd command.

NOTE

   You can create a root account only during a Fedora install. You will have to create user accounts after booting, using a command-line program (such as adduser) or the graphical system-config-users client. Create an account for yourself and any additional users. Usernames traditionally consist of the first letter of a person's first name and then the last name. For example, Tom Denning would have a username of tdenning. Do not forget to enter a password for any new user! If you create a user without a creating a password, the new user will not be able to log in.
   You should create at least one user for your server in addition to the root operator. This is for security purposes and to avoid logging in as root, either through the keyboard at the server or remotely over the network. The default shell and home directory settings should remain set at the defaults, which are the Bourne Again SHell (bash) and the /home directory.
   See Chapter 4, "Command-Line Quick Start," for how to become the root user or run root commands as a regular user. See Chapter 10 for details on managing users.

TIP

   Good passwords are essential for system security. However, some people still rely on passwords as simple as admin. This is asking for trouble, and we would encourage you to create a strong password made up of letters, numbers, and even punctuation. It can be difficult to create a password that is easily memorable and that includes punctuation, but it can be simpler than you think. For instance, George Nedeff may want to use his full name as a password, but that would be easy to crack. What he could do is use punctuation and numbers to replace similar letters in his name, such as G30rg3n3defF. This is a very strong password, and not easily broken, but at the same time it is very easy to remember.

What Happened to Install Everything?

   In previous versions of Fedora and Red Hat Linux, there was an option to install every thing available. This has now been removed from Fedora for a number of reasons. First of all, installing all the packages can create dependency nightmares when upgrading and installing new packages. Second, there can be too many packages for new users to handle. Third, and perhaps most important, it can pose a huge security risk to your system. The more software you have installed, the greater the risk that someone could find a vulnerable entry point into your system.

NOTE

   Fedora can enter your own repositories at install time. Fedora takes these new repositories into account when you go through the Customize Packages screens. All you have to do is provide a name for the repository, as well as the FTP or HTTP server and path details to the repomd.xml file. Just click the Add Repository button to do this.

NOTE

   After installation, you can edit the file /boot/grub/grub.conf and change the timeout= setting to change the boot time to a value other than 5 seconds.

NOTE

   To read the end-user licensing agreement for Fedora, go to http://fedoraproject.org/wiki/Legal/Licenses/EULA.

SELinux

   As mentioned earlier, SELinux came from the NSA (National Security Agency), one of the most secret organizations in the United States. The community's shock at having this technology released to them can be summed up by Larry Loeb when he said, "Let me assure you that this action by the NSA was the crypto-equivalent of the pope coming down off the balcony in Rome, working the crowd with a few loaves of bread and some fish, and then inviting everyone to come over to his place to watch the soccer game and have a few beers. There are some things that one just never expects to see, and the NSA handing out source code along with details of the security mechanism behind it was right up there on that list."

NOTE

   So we said that all your personalized settings are stored in your home directory, but when you open it up you find that you can't see anything but the default directories. This is because all your personalized settings are stored in hidden folders, commonly prefixed with a period. Simply go to the View menu and select Show Hidden Files and suddenly you'll see all the folders related to your settings.

NOTE

   Fedora doesn't ship with MP3 support as standard, nor does it include support for many of the standard formats found within Windows or Mac OS X. This is down to the patents that are used in the development of these formats, more commonly known as codecs. Inclusion of these codecs in Fedora is prevented due to the legality of the licenses and patents involved. However, all is not lost. Some third-party repositories offer plug-ins for the multimedia applications bundled with Fedora, which allow them to use additional codecs.

NOTE

   A full installation of X and related X.Org 7.3 files can consume more — usually much more — than 170MB of hard drive space. This happens because additional clients, configuration files, and graphics (such as icons) are under the /usr/bin and /usr/share directory trees. You can pare excessive disk requirements by judiciously choosing which X-related packages (such as games) to install on workstations. However, with the increased capacity of most desktop PC hard drives today, the size requirements are rarely a problem, except in configuring thin-client desktops or embedded systems.

The ServerLayout Section

The Files Section

The Module Section

The InputDevice Section

NOTE

   If you change your computer's pointing device, you should then run Fedora's system-config-mouse client, which automatically updates your system's xorg.conf file.

CAUTION

   From Fedora Core 3 onward, the location for the mouse device changed from /dev/mouse to /dev/input/mice. Unfortunately, when system-config-display writes the xorg.conf file, it sometimes gets a little confused and still maps the mouse to /dev/mouse rather than /dev/input/mice. This is where a little knowledge of vi comes in handy!

The Monitor Section

The Device Section

The Screen Section

NOTE

   If your monitor and graphics card support multiple resolutions and the settings are properly configured, you can use the key combination of Ctrl+Alt+Keypad+ or Ctrl+Alt+Keypad to change resolutions on-the-fly during your X session.

Configuring X with the system-config-display Client

Using Xorg to Configure X

Configuring gdm

Configuring kdm

Using the xdm Display Manager

TIP

   Those of you who have used a computer for many years will probably have come into contact with MS-DOS, in which case being presented with a black screen will fill you with a sense of nostalgia. Do not get too comfy; the command line in Linux is far superior to its distant MS-DOS cousin. Whereas MS-DOS skills are transferable only to other MS-DOS environments, the skills that you learn at the Linux command line can be transferred easily to other UNIX-like operating systems, such as Solaris, OpenBSD, FreeBSD, and even Mac OS X (because it allows you access to a terminal).

Security

   One concept you will have to get used to is that of user-based security. By and large, only two types of users will access the system as actual users. The first type is the regular user, of which you created one when you started Fedora for the first time (see Chapter 1, "Installing Fedora"). These users can change anything that is specific to them, such as the wallpaper on the desktop, their personal preferences, and so on. These users are prevented from making changes that will affect other users than themselves, sometimes called systemwide changes.
   To make systemwide changes, you need to use the super-user or root account. This is a special-access privilege that gives you complete control over the entire system, with the ability to destroy everything should you so want. If you have installed Linux on your own PC, you automatically have access to the root account as you set it up during the installation. However, it is not unusual for users to not have any access to the root user, especially in corporate environments where security and system stability are of paramount importance.
   An example of the destructive nature of root can be found in the age-old example of #rm -rf /, which erases all the data on your hard drive. You need to be especially careful when working as root; otherwise, you might irreparably damage your system. Don't let this worry you, however, because the root user is fundamental to a healthy Linux system. Without it you would not be able to install new software, edit system configuration files, or do any number of administration tasks. By the end of this chapter, you will feel comfortable working as root and be able to adequately administer your system.

TIP

   This is actually one of six virtual consoles that Fedora provides for your use. After you have accessed a virtual console, you can use the Alt key and F1 through F6 to switch to a different console. If you want to get back to the graphical interface, press Alt+F7. You can also switch between consoles by holding the Alt key and pressing either the left or the right cursor key to move down or up a console, such as vt1 to vt2.

TIP

   Navigating through the system at the command line can get confusing at times, especially when a directory name occurs in several different places. Fortunately, Linux includes a simple command that tells you exactly where you are in the file system. It's easy to remember because the command is just an abbreviation of present working directory, so type pwd at any point to get the full path of your location. For example, typing pwd after following these instructions shows /home/yourusername, meaning that you are currently in your home directory.
   Using the pwd command can save you a lot of frustration when you have changed directory half a dozen times and have lost track.

CAUTION

   Don't forget the pwd command to remind you where you are within the file system!

NOTE

   Learn more about using expressions by reading the ex or grep manual pages.

CAUTION

   If you are new to Linux, the system-config-keyboard client is the best tool to use to configure a keyboard. You should manually edit system hardware configuration files used by graphical management clients only as a last resort.

NOTE

   The Linux kernel has a number of built-in protections, but good system administration security policies and a secure firewall protecting your gateway, router, or Internet-connected system are the best protection you can use. See Chapter 30, "Securing Your Machines," for an overview of firewalling and examples of how to implement network security tools included with Fedora.

NOTE

   This chapter focuses on text-based logins and use of Linux. Graphical logins and using a graphical desktop are described in Chapter 3.

NOTE

   Note that your password is not echoed back to you, which is a good idea. Why is it a good idea? Well, people are prevented from looking over your shoulder and seeing how many characters are on your screen. It is not difficult to guess that a five-letter pass word might correspond to the user's spouse's first name!

NOTE

   See Chapter 14, "Networking," to see how to set up network interfaces with Linux to support remote network logins and Chapter 11 to see how to start remote access services (such as sshd).

NOTE

   Each shell can have its own feature set and language syntax, as well as a unique set of default environment variables. See Chapter 15, "Remote Access with SSH," for more information about using the different shells included with Fedora.

NOTE

   See the bash man page for other variables you can use for prompt settings.

NOTE

   Use the vimtutor command to quickly learn how to use vi's keyboard commands. The tutorial takes less than 30 minutes, and it teaches new users how to start or stop the editor; navigate files; insert and delete text; and perform search, replace, and insert operations.

TIP

   If you start emacs when using X11, the editor launches in its own floating window. To force emacs to display inside a terminal window rather than its own window (which can be useful if the window is a login at a remote computer), use the -nw command-line option like this:emacs -nw file.txt.

TIP

   One of the best reasons to learn how to use emacs is that you can use nearly all the same keystrokes to edit commands on the bash shell command line. Another reason is that like vi, emacs is universally available on nearly every UNIX and Linux system, including Apple's Mac OS X.

CAUTION

   Before editing any important system or software service configuration file, make a backup copy. Then make sure to launch your text editor with line wrapping disabled. If you edit a configuration file without disabling line wrapping, you could insert spurious carriage returns and line feeds into its contents, causing the configured service to fail when restarting. By convention, nearly all configuration files are formatted for 80-character text width, but this is not always the case. By default, the vi and emacs editors don't use line wrap.

NOTE

   In this chapter, you learn how to manage users from the command line. See Chapter 10 for more information on user administration with Fedora using graphical administration utilities, such as the system-config-users client.

TIP

   Do not shut down your computer if you suspect that one or more intruders has infiltrated your system; instead, disconnect the machine from any or all networks and make a backup copy of your hard drives. You might want to also keep the machine running to examine the contents of memory and to examine system logs. See Chapter 14 and Chapter 30, "Securing Your Machines," for how to protect and monitor a network-connected system.

NOTE

   Checking Fedora's website for security updates and bug fixes is a good idea. Browse to http://fedoraproject.org/wiki/. Alternatively, you can always do a quick yum update to make sure that your system has the most up-to-date software available.

NOTE

   Although nearly all the hundreds of GNU commands included with Linux each have a man page, you must use the info command to read detailed information about using a GNU command. For example, to learn even more about bash (which has a rather extensive manual page), use the info command like this:
   $ info bash
   Press the n and p keys to navigate through the document, or scroll down to a menu item on the screen and press Enter to read about a specific feature. Press q to quit reading.

Related Fedora and Linux Commands

   The following programs and built-in shell commands are commonly used when working at the command line. These commands are organized by category to help you under stand the command's purpose. If you need to find full information for using the command, you can find that information under the command's man page.
   ► Managing users and groups — chage, chfn, chsh, edquota, gpasswd, groupadd, groupdel, groupmod, groups, mkpasswd, newgrp, newusers, passwd, umask, useradd, userdel, usermod
   ► Managing files and file systems — cat, cd, chattr, chmod, chown, compress, cp, dd, fdisk, find, gzip, ln, mkdir, mksfs, mount, mv, rm, rmdir, rpm, sort, swapon, swapoff, tar, touch, umount, uncompress, uniq, unzip, zip
   ► Managing running programs — bg, fg, kill, killall, nice, ps, pstree, renice, top , watch
   ► Getting information — apropos, cal, cat, cmp, date, diff, df, dir, dmesg, du, env, file, free, grep, head, info, last, less, locate, ls, lsattr, man, more, pinfo, ps, pwd, stat, strings, tac, tail, top, uname, uptime, vdir, vmstat, w, wc, whatis, whereis, which, who, whoami
   ► Console text editors — ed, jed, joe, mcedit, nano, red, sed, vim
   ► Console Internet and network commands — bing, elm, ftp, host, hostname, ifconfig, links, lynx, mail, mutt, ncftp, netconfig, netstat, pine, ping, pump, rdate, route, scp, sftp, ssh, tcpdump, traceroute, whois, wire-test

A Brief Introduction to the Internet

   The Internet itself was first brought to life by the U.S. Department of Defense in 1969. It was called ARPANet after the Department of Defense's Advanced Research Projects Agency. Designed to build a network that would withstand major catastrophe (this was the peak of the Cold War), it soon grew to encompass more and more networks to build the Internet. Then, in 1991, Tim Berners-Lee of CERN developed the idea of the World Wide Web, including Hypertext Transfer Protocol (HTTP) and Hypertext Markup Language (HTML). This gave us what we now know to be the Internet.

TIP

   If you connect to the Internet using a dialup modem, make sure you don't check the Checking for New Mail option; otherwise, you might find that you will be connecting every 10 minutes.

A Brief History of OpenOffice.org

   The OpenOffice.org office suite is based on a commercial suite called StarOffice. Originally developed by a German company, StarOffice was purchased by Sun Microsystems in the United States. One of the biggest complaints about the old StarOffice was that all the component applications were integrated under a StarOffice "desktop" that looked very much like a Microsoft Windows desktop, including a Start button and menus. This meant that to edit a simple document, unneeded applications had to be loaded, making the office suite slow to load, slow to run, and quite demanding on system resources.
   After the purchase of StarOffice, Sun Microsystems released a large part of the StarOffice code under the GPL (GNU Public License), and development began on what has become OpenOffice.org, which is freely available under the GPL. Sun continued development on StarOffice and released a commercial version as StarOffice 6.0. The significant differences between the free and commercial versions of the software are that StarOffice provides more fonts and even more import/export file filters than OpenOffice.org (these filters cannot be provided in the GPL version because of licensing restrictions) and StarOffice provides its own relational database, Software AG's Adabas D database. The StarOffice counterpart to OpenOffice.org 2.3 is StarOffice 8.

TIP

   OpenOffice.org is constantly improving its productivity applications. You can check the OpenOffice.org website (http://www.openoffice.org/) for the latest version. The website provides a link to download the source or a precompiled version of the most current working installation files. A more current version might offer file format support that you need. Should you need a Windows-compatible version, you will also find it at the website.

TIP

   Two websites provide additional information on the functionality of OpenOffice.org:
   ► http://lingucomponent.openoffice.org/download_dictionary.html — This site provides instructions and files for installing spelling and hyphenation dictionaries, which are not included with OpenOffice.org.
   ► http://sourceforge.net/projects/ooextras/ — This site provides templates, macros, and clip art, which are not provided with OpenOffice.org.

NOTE

   You might be interested to know that Writer was the primary word processor chosen to write and edit this book.

Getting Started

Working with Styles and Formatting

Getting Started

TIP

   Calc offers some nifty little features that you can use quickly if you need to. The handiest one in our opinion is the capability to select multiple cells and see immediately the total and average of the range. You will find these figures in the bottom-right status bar. This has saved us numerous times when we have needed to get this information quickly!

Formatting Your Spreadsheets

Summarizing Data with Calc

NOTE

   The decision by the state of Massachusetts to standardize on PDF and OpenDocument has huge ramifications for the open source world. It is the first time that OpenDocument, an already-agreed open standard, has been specified in this way. What it means is that anyone who wants to do business with the state government must use OpenDocument-based file formats, and not the proprietary formats in use by Microsoft. Unfortunately for Microsoft, it does not have support for OpenDocument in any of its applications, making them useless to anyone wanting to work with the state government. This is despite Microsoft being a founding member of OASIS, who developed and ratified the OpenDocument standard!

The GTK Widget Set

   Open source developers are always trying to make it easier for people to build applications and help in development. To this end, there are a number of widgets or toolkits that other developers can use to rapidly create and deploy GUI applications. These widgets control things such as drop-down lists, Save As dialogs, window buttons, and general look and feel. Unfortunately, whereas Windows and Apple developers have to worry about only one set of widgets each, Linux has a plethora of different widgets, including GTK+, QT, and Motif. What is worse is that these widgets are incompatible with one another, making it difficult to easily move a finished application from one widget set to another.
   GTK is an acronym for GIMP Tool Kit. The GIMP (The GNU Image Manipulation Program) is a graphics application very similar to Adobe Photoshop. By using the GTK-based jargon, we save ourselves several hundred words of typing and help move along our discussion of GNOME Office. You might also see similar references to QT and Motif, as well as to other widget sets, in these chapters.

Commercial Office Suites for Linux

   Several commercial office suites are available for Fedora in addition to StarOffice, already mentioned. None of these commercial suites are provided with Fedora. Of note is Hancom Office. Using the same QT widget set found in the KDE desktop, Hancom Office scores well on Microsoft file format compatibility. The suite includes a word processor, a spreadsheet presentation tool, and a graphics application. Corel produced a version of its WordPerfect Office 2000 for Linux before it discontinued the release of any new Linux products. It still offers a support page, but the software is no longer available, nor is the excellent — but whiskered — WordPerfect 8 for Linux.

Getting Music into Fedora with Sound Juicer

   A handy utility that is included with Fedora is Sound Juicer, found under Applications, Sound and Video. Sound Juicer automatically detects when you install a CD and attempt to retrieve the track details from the Internet. From there it will rip the CD tracks into Ogg files for storage on your filesystem. You can see Sound Juicer in action in Figure 7.4.

NOTE

   The Icecast application, not provided with Fedora, is a popular streaming audio server. You can use Icecast to serve your MP3 music collection over your home LAN. You can learn more about Icecast at http://www.icecast.org/. A nice tutorial on Icecast is available athttp://www.linuxnetmag.com/en/issue4/m4icecast1.html.

What Does Photoshop Have That Isn't in The GIMP?

   Although The GIMP is powerful, it does lack two features Adobe Photoshop offers that are important to some graphics professionals.
   The first of these is the capability to generate color separations for commercial press printers (CMYK for the colors cyan, magenta, yellow, and key [or black]). The GIMP uses RGB (red, green, and blue), which is great for video display, but not so great for printing presses. The second feature The GIMP lacks is the use of Pantone colors (a patented color specification) to ensure accurate color matching.
   If these features are unimportant to you, The GIMP is an excellent tool. If you must use Adobe Photoshop, the current version of CodeWeavers' CrossOver Office will run Photoshop in Linux.
   These deficiencies might not last long. A CMYK plug-in is in the works, and the Pantone issues are likely to be addressed in the near future as well.

NOTE

   Although xsane is commonly used as a GIMP plug-in, it can also be used as a standalone program. Another useful program is Joerg Schulenburg's gocr client, used for optical character recognition (OCR). Although not a standalone application, it is included in the Kooka scanning application. This program works best with 300 dots per inch (dpi) scans in several different graphics formats. OCR is a resource-intensive task and can require hundreds of megabytes of disk storage!

TIP

   Fedora includes dozens of graphics conversion programs that are accessible through the command line, and there are few, if any, graphics file formats that cannot be manipulated when using Linux. These programs can be called in Perl scripts, shell scripts, or command-line pipes to support many types of complex format conversion and image manipulation tasks. See the man pages for the ppm, pbm, pnm, and pgm families of commands. Also see the man page for the convert command, which is part of a suite of extremely capable programs included with the ImageMagick suite.

Fun with ImageMagick's identify

   You can use ImageMagick's identify command to identify details about image files. The welcoming splash image used for the GRUB bootloader is located in /boot/grub and is a gzipped .xpm image. If you run identify on the image, you'll discover that it's a 640×480 xpm image with 16-bit color depth. That's all you need to know to construct a replacement image of your own. Using The GIMP or another graphics tool, crop or resize your chosen image to 640×480 and change the color depth to 16 bits. Save the image as splash.xpm and then gzip the resulting file. Replace the original Fedora file, and you now have a custom boot image. The use of identify helped you duplicate the parameters of the original image to comply with the requirements of GRUB. The identify command is also useful to identify unknown image files and to determine whether they're corrupt.

Nautilus

GnomeBaker

TIP

   An excellent Internet site for CD-related information is http://www.cdmediaworld.com/. The Gracenote CDDB Music Recognition Service licenses a database service to soft ware developers so that they can include additional functionality in their applications by accessing the database and having their applications display information about the music CD, including the artist and song title, the CD's track list, and so on. The data base server at cddb.cddb.org, when contacted by the appropriate software, identifies the appropriate CD and sends the information to be displayed locally. Many CD player applications provide this functionality. The service is interactive: If you have a CD that is not in the CDDB database, the website tells you how you can add the information to the database.

NOTE

   You can also use the blank= option with the cdrecord command to erase CD-RW disks. The cdrecord command has fewer options than mkisofs does, but it offers the -multi option, which enables you to make multisession CDs. A multisession CD enables you to write a data track, quit, and then add more data to the CD later. A single-session CD can be written to only once; any leftover CD capacity is wasted. Read about other options in the cdrecord man page.
   Current capacity for CD media is 700MB of data or 80 minutes of music. (There are 800MB/90 minute CDs, but they are rare.) Some CDs can be overburned; that is, recorded to a capacity in excess of the standard. The cdrecord command is capable of overburning if your CD-RW drive supports it. You can learn more about overburning CDs athttp://www.cdmediaworld.com/hardware/cdrom/cd_oversize.shtml/.

TIP

   The 4.7GB size of DVD media is measured as 1000 megabytes per gigabyte, instead of the more commonly used 1024 megabytes per gigabyte, so do not be surprised when the actual formatted capacity, about 4.4GB, is less than you anticipated. dvd+rw-tools does not allow you to exceed the capacity of the disk.

Session Writing

CAUTION

   Some DVDs come preformatted; formatting them again when you use them for the first time can make the DVD useless. Always be sure to carefully read the packaging your DVD comes in to ensure that you are not about to create another coaster!

TIP

   Writing a first session of at least 1GB helps maintain compatibility of your recorded data with other optical drives. DVD players calibrate themselves by attempting to read from specific locations on the disk; you need data there for the drive to read it and calibrate itself.
   Also, because of limitations to the ISO9660 file system in Linux, do not start new sessions of a multisession DVD that would create a directory past the 4GB boundary. If you do so, it causes the offsets used to point to the files to "wrap around" and point to the wrong files.

Packet Writing

TIP

   DVD+RW media are capable of only about 1,000 writes, so it is very useful to mount them with the noatime option to eliminate any writing to update their inodes or simply mount them read-only when it's not necessary to write to them.

   "The original graphics work for computers was done by Evans & Sutherland on Unix systems. The innovations at MIT's Media Lab were done on Unix workstations. In 1985, we at HP Labs were creating sophisticated multimedia immersive work environments on Unix workstations, so maybe Unix is more multimedia than suggested. Limitations in Linux support doesn't mean Unix had the same limitations. I think it was more a matter of logistics, with hundreds of sound cards and thousands of different possible PC configurations."

NOTE

   Because of patent and licensing issues, Fedora has removed support for the MPEG, MPEG2, and MPEG3 (MP3) file formats in Fedora Linux. Although we cannot offer any legal advice, it appears that individuals using MP3 software are okay; it is just that Fedora cannot distribute the code because it sells its distribution. It seems — at this point — perfectly all right for you to obtain an MP3-capable version of Xmms (for example), which is a Winamp clone that plays MPEG1/2/3 files. You can get Xmms directly from http://www.xmms.org/ because that group has permission to distribute the MP3 code.
   You can also enable the MP3 codec within Fedora by using the livna.org yum repository. You do this by installing the gstreamer-plugins-mp3 package, which enables the MP3 codec in all the GNOME applications.
   Another alternative is to use the Ogg-Vorbis format; it is completely free of restrictions. A ripper for CD music is available from http://www.thekompany.com/projects/tkcoggripper/ and an MP3-to-Ogg converter is available from http://faceprint.com/ code/. Or, you could download and install the non-crippled versions of multimedia applications from FreshRPMs athttp://www.freshrpms.net/.

TIP

   To learn more about the technical details of audio formats, read Chris Bagwell's Audio Format FAQ athttp://www.cnpbagwell.com/audio.html.

TIP

   Other useful documentation can be found in /usr/src/linux-2.6/Documentation/_video4linux. After you have identified a driver for a device, it does not hurt to look at the source code for it because so little formal documentation exists for many drivers; much of it is in the source code comments.

TIP

   An RPM that provides a Divx codec for Linux can be found at http://www.freshrpms.net/. Divx is a patented MPEG-4 video codec that is the most widely used codec of its type. It allows for compression of MPEG-2 video by a factor of 8. See http://www.divx. com/ for more information.
   The GetCodecs application is a Python script with a GUI interface that downloads, installs, and configures your Fedora system with multimedia codecs not provided by Fedora, such as MP3, Divx, and DVD codecs. The script can be obtained from http://sourceforge.net/projects/getcodecs/.

Macromedia Flash

   The Macromedia Flash plug-in for the Mozilla browser is a commercial multimedia application that isn't provided with Fedora, but many people find it useful. Macromedia Flash enables you to view Flash content at websites that support it. The Mozilla plug-in can be obtained from http://macromedia.mplug.org/. Both .rpm and .tar.gz files are provided.
   Having trouble with the Macromedia Flash plug-in for Mozilla? Just manually copy the files flashplayer.xpt and libflashplayer.so to /usr/lib/firefox-2.0.0.x/plugins, where x is the latest point release for Firefox (2.0.0.4 at the time of writing). An .rpm file for Flash that should install without problems is available from http://macromedia.mplug.org/.

Linux, TiVo, and PVRs

   Some TiVo users say that using this Linux-based device has changed their lives. Indeed, the convenience of using a personal video recorder (PVR) can make life a lot easier for inveterate channel surfers. Although PVR applications are not included with Fedora, open source developers are working on newer and better versions of easy-to-install and easy-to-use PVR software for Linux. For more information about TiVo, which requires a monthly charge and a phone line (or broadband connection with a newer TiVo2), browse to http://www.tivo.com/. Unrepentant Linux hardware hackers aiming to disembowel or upgrade a TiVo can browse to http://www.9thtee.com/tivoupgrades.htm or read the TiVo Hack FAQ at http://www.tivofaq.com/. A PVR makes viewing television a lot more fun!
   A number of Linux sites are devoted to PVR software development. Browse to the DVR project page athttp://www.pierrox.net/dvr/.

NOTE

   The VideoLAN HOWTO found at http://videolan.org/ discusses the construction of a network for streaming video. Although you might not want to create a network, a great deal of useful information about the software and hardware involved in the enterprise can be generalized for use elsewhere, so it is worth a look. The site also contains a link to a HOWTO about cross-compiling on Linux to produce a Windows binary.

CAUTION

   Do not manually edit your /etc/printcap. Any changes will be lost when the printing service is restarted or if your system is rebooted. If you need to create customized printer entries, save the entries in /etc/printcap.local and then restart the printing service.

NOTE

   The system-config-printer utility is an update to the now-legacy printtool client included with previous Red Hat Linux distributions. Although you might also find related tools (or symbolic links), such as printtool, printconf-tui, and /usr/sbin/printconf-gui installed on your system, you should use the system-config-printer client to manage printers under Fedora.

NOTE

   Fedora includes graphical clients you can use to view many different types of documents. For example, to display PostScript documents (including compressed PostScript documents) or PostScript images, use the gv client. To display Portable Document Format (PDF) documents, you can use gv or the xpdf client.

Aladdin or GNU?

   At least two versions of Ghostscript are available for Linux. One version is named AFPL Ghostscript, which formerly went by the name Aladdin Ghostscript. This version is licensed under the Aladdin Free Public License, which disallows commercial distribution. The other version is called GNU Ghostscript, which is distributed under the GNU General Public License. For details about the different versions or for answers to questions regarding licensing, see the Ghostscript home page at http://www.cs.wisc.edu/~ghost/.

NOTE

   You can also browse to http://www.linuxprinting.org/ to find out what drivers to use with your printer or to see a cross-referenced listing of printers supported by each driver. You might also find new and improved drivers for the latest printers on the market.

TIP

   You can also configure multiple print queues for the same printer. Use this technique to test printing using different print drivers with the same printer. Create a new queue, give it a specific name (such as testpcl3), and select a different printer. Finish the configuration and print a test page to compare the results against other entries to find the best output. You can also use this technique to define a monochrome or color printer entry for the same printer or to use different drivers for different types of media (such as regular or photo paper).

Related Fedora and Linux Commands

   The following commands help you manage printing services:
   ► accept — Controls print job access to the CUPS server via the command line
   ► cancel — Cancels a print job from the command line
   ► cancel — Command-line control of print queues
   ► disable — Controls printing from the command line
   ► enable — Command-line control CUPS printers
   ► lp — Command-line control of printers and print service
   ► lpc — Displays status of printers and print service at the console
   ► lpq — Views print queues (pending print jobs) at the console
   ► lprm — Removes print jobs from the print queue via the command line
   ► lpstat — Displays printer and server status
   ► system-config-printer — Fedora's graphical printer configuration tool

CAUTION

   The Livna repository is home to not only a wide range of kernel modules and drivers for many popular items of hardware, but also contains a number of legally question able packages that are not enabled in Fedora by default, including native MP3 support. If you are using Fedora for personal use, you should not have any real problems, but make sure to check before you start installing packages from Livna onto a corporate workstation or server!

CAUTION

   Both sets of graphics card drivers are very dependent on the kernel version you are running. Every time you update your kernel, you also have to update your driver. If you have used the kmod-* package from Livna, it should automatically update when you run yum upgrade.

NOTE

   On your Fedora system, when you log in as root, you are root or the super user. In this chapter, the terms root, super user, system administrator, and sysadmin are used interchangeably, although they need not all refer to a single person.

CAUTION

   Because of the potential for making a catastrophic error as the super user (using the command rm -rf /* is the classic example, but do not ever try it!), always use your system as a regular user and become root only temporarily to do sysadmin duties. While you are on a multiuser system, consider this advice an absolute rule; if root were to delete the wrong file or kill the wrong process, the results could be disastrous for the business. On your home system, you can do as you please and running as root makes many things easier, but less safe. In any setting, however, the risks of running as root full time are significant. (In case you're wondering, the above command would completely wipe your entire file system, leaving you with nothing but a red face!)

NOTE

   A Linux username can be any alphanumeric combination that does not begin with a special character reserved for shell script use (see Chapter 11, "Automating Tasks," for disallowed characters, mostly punctuation characters). Usernames are typically the user's first name plus the first initial of her last name, something that is a common practice on larger systems with many users because it makes life simpler for the sysadmin, but is neither a rule nor a requirement.

CAUTION

   If you intend to make use of NFS, it is extremely important that you use the same UID for the user on the host and guest machines; otherwise, you will not be able to connect!

User Stereotypes

   As is the case in many professions, exaggerated characterizations (stereotypes or caricatures) have emerged for users and system administrators. Many stereotypes contain elements of truth mixed with generous amounts of hyperbole and humor and serve to assist us in understanding the characteristics of and differences in the stereotyped subjects. The stereotypes of the "luser" and the "BOFH" (users and administrators, respectively) also serve as cautionary tales describing what behavior is acceptable and unacceptable in the computing community.
   Understanding these stereotypes allows you to better define the appropriate and inappropriate roles of system administrators, users, and others. The canonical reference to these terms is found in the alt.sysadmin.recovery FAQ found at http://www.ctrl-c.liu.se/~ingvar/asr/.

NOTE

   The set of files initially used to populate a new user's home directory are kept in /etc/skel. This is convenient for the system administrator because any special files, links, or directories that need to be universally applied can be placed in /etc/skel and will be duplicated automatically with appropriate permissions for each new user.
   # ls -al /etc/skel
   total 60
   drwxr-xr-x   4 root root  4096 2007-10-21 19:58 .
   drwxr-xr-x 112 root root 12288 2007-10-22 20:40 ..
   -rw-r--r--   1 root root    33 2007-08-31 15:20 .bash_logout
   -rw-r--r--   1 root root   176 2007-08-31 15:20 .bash_profile
   -rw-r--r--   1 root root   124 2007-08-31 15:20 .bashrc
   drwxr-xr-x   2 root root  4096 2007-10-17 17:52 .gnome2
   Each line provides the file permissions, the number of files housed under that file or directory name, the file owner, the file group, the file size, the creation date, and the filename.
   As you can see, root owns every file here, but the adduser command (a symbolic link to the actual command named useradd) copies everything in /etc/skel to the new home directory and resets file ownership and permissions to the new user. Certain user files might exist that the system administrator does not want the user to change; the permissions for those files in /home/username can be reset so that the user can read them but can't write to them.

TIP

   To lock a user out of his account, use the following command:
   # passwd -l username
   This prepends a double ! (exclamation point, also called a bang) to the user's encrypted password; the command to reverse the process uses the -u option. This is a more elegant and preferred solution to the problem than the traditional UNIX way of manually editing the file.

TIP

   Interestingly, a phenomenon known as timewarp can occur in which an entry in the wtmp files jumps back into the past and ac shows unusual amounts of connected time for users. Although this can be attributed to some innocuous factors having to do with the system clock, it is worthy of investigation by the sysadmin because it can also be the result of a security breach.

NOTE

   The accounting system on your computer keeps track of user usage statistics and is kept in the current /var/log/wtmp file. That file is managed by the init and login processes. If you want to explore the depths of the accounting system, use the GNU info system: info accounting.

NOTE

   In Linux, you can create groups to assign a number of users access to common directories and files based on permissions. You might assign everyone in accounting to a group named accounting, for example, and allow that group access to accounts payable files while disallowing access by other departments. Defined groups are maintained by the root operator, but you can use the newgrp command to temporarily join other groups to access files (as long as the root operator has added you to the other groups). You can also allow or deny access to your files by other groups by modifying the group permissions of your files.

NOTE

   Other files that might have suid or guid permissions include at, rcp, rlogin, rsh, chage, chsh, ssh, crontab, sudo, sendmail, ping, mount, and several UNIX-to-UNIX Copy (UUCP) utilities. Many programs (such as games) might also have this type of permission to access a sound device.

NOTE

   The find command is quite helpful and can be used for many purposes, such as before or during backup operations. See the section "Using Backup Software" in Chapter 13, "Backing Up."

PAM Explained

   Pluggable Authentication Modules (PAM) is a system of libraries that handle the tasks of authentication on your computer. It uses four management groups: account management, authentication management, password management, and session management. This allows the system administrator to choose how individual applications will authenticate users. Fedora has preinstalled and preconfigured all the necessary PAM files for you.
   The configuration files in Fedora are found in /etc/pam.d. These files are named for the service they control, and the format is as follows:
   type control module-path module-arguments
   The type field is the management group to which the rule corresponds. The control field tells PAM what to do if authentication fails. The final two items deal with the PAM module used and any arguments it needs. Programs that use PAM typically come pack aged with appropriate entries for the /etc/pam.d directory. To achieve greater security, the system administrator can modify the default entries. Misconfiguration can have unpredictable results, so back up the configuration files before you modify them. The defaults provided by Fedora are adequate for home and small office users.
   An example of a PAM configuration file with the formatted entries as described previously is shown next. Here are the contents of /etc/pam.d/system-config-users:
   #%PAM-1.0
   auth    include config-util
   account include config-util
   session include config-util
   Amusingly, even the PAM documents state that you do not really need (or want) to know a lot about PAM to use it effectively.
   You will likely need only the PAM system administrator's guide. Look under the /usr/share/doc/pam* directory for additional documents in PostScript, text, and HTML formats.

NOTE

   A popular misconception is that the su command is short for super user; it just means substitute user. An important but often overlooked distinction is that between su and su -. In the former instance, you become that user but keep your own environmental variables (such as paths). In the latter, you inherit the environment of that user. This is most noticeable when you use su to become the super user, root. Without appending the -, you do not inherit the path variable that includes /bin or /sbin, so you must always enter the full path to those commands when you just su to root.

TIP

   It is never a good idea to use an Internet Relay Chat (IRC) client as the root user, and you might not want to run it using your regular user account. Just create a special new user just for IRC and su to that user in a terminal widow to launch your IRC client.

NOTE

   No graphical tools supported by Fedora can be used to configure disk quotas. A Quota mini-HOWTO is maintained at http://www.tldp.org/HOWTO/Quota.html.

Related Fedora Commands

   You will use these commands to manage user accounts in Fedora:
   ► ac — A user account-statistics command
   ► change — Sets or modifies user password expiration policies
   ► chfn — Creates or modifies user finger information in /etc/passwd
   ► chgrp — Modifies group memberships
   ► chmod — Changes file permissions
   ► chown — Changes file ownerships
   ► chpasswd — Batch command to modify user passwords
   ► chsh — Modifies a user's shell
   ► groups — Displays existing group memberships
   ► logname — Displays a user's login name
   ► newusers — Batches user management command
   ► passwd — Creates or modifies user passwords
   ► su — Executes shell or command as another user
   ► sudo — Manages selected user execution permissions
   ► system-config-users — Fedora's graphical user management tool
   ► useradd — Creates, modifies, or manages users
   ► userinfo — Fedora's graphical chfn command
   ► usermod — Edits a user's login profile
   ► userpasswd — Fedora's graphical user password command

NOTE

   If the BIOS detects a hardware problem, the boot process fails and the BIOS generates a few beeps from the system speaker. These "beep codes" indicate the nature of the problem the BIOS has encountered. The codes vary among manufacturers, and the diagnosis of problems occurring during this phase of the boot process is beyond the scope of this book and does not involve Linux. If you encounter a problem, you should consult the motherboard manual or contact the motherboard's manufacturer.

NOTE

   Linux is very flexible and can be booted from multiple images on a CD-ROM, over a network using PXE (pronounced "pixie") or NetBoot, or on a headless server with the console display sent over a serial or network connection. Work is even underway to create a special Linux BIOS at http://www.linuxbios.org/ that expedites the boot process because Linux does not need many of the services offered by the typical BIOS.
   This kind of flexibility enables Linux to be used in a variety of ways, such as remote servers or diskless workstations, which are not generally seen in personal home use.

NOTE

   Details about the sequence of events that occur when the Linux kernel is loaded can be found in the file /usr/src/iinux-2.6/init/main.c if you installed the Linux kernel documentation.

NOTE

   The System V method makes extensive use of symbolic links, which are ways to reference a file in another location and make it appear as if it were in two or more places at once. The benefit is that you need to edit only one file to change them all. In addition, any reorganization to be done means that only links need to be changed, not the files themselves.

NOTE

   Not all Linux distributions use the same runlevel configurations or runlevel definitions! For example, although Fedora uses runlevel 3 for a full, console-based multiuser mode, pre-7.1 versions of SUSE Linux defined this system state as runlevel 2. Red Hat, Fedora, and SUSE now use the same runlevels to conform to the Linux Standards Base, or LSB. As a system administrator, you should be aware of this issue, especially if you have devised any administrative scripts or tools that deal with system states.

CAUTION

   Never forget that uncontrolled physical access is virtually a guarantee of access to your data by an intruder.

NOTE

   If you have enabled a GRUB password, you must first press p, type your password, and then press Enter before using this boot method.

TIP

   You can write your own init scripts, using the existing scripts as examples. Sample scripts can also be found in /usr/share/doc/initscripts/sysvinitfiles, along with a brief tutorial written by Red Hat and a brief explanation of all the options available to use in init scripts.

Using the chkconfig Text-Based Command-Line Tool

NOTE

   ntsysv is simple to use and it's an excellent tool for a system without X, but it works for only the runlevel in which you are currently. Use the --level option to modify other runlevels.

Using the GUI-Based Service Configuration Tool

TIP

   Linux is full of shortcuts: If you exit the single-user shell by typing exit at the prompt, you go back to the default runlevel without worrying about using telinit.

CAUTION

   The cron daemon reads all the system crontab files and all user crontab files once a minute (on the minute; that is, at 6:00:00, 6:01:00, and so on) to check for changes. However, any new jobs it finds are not executed until at least one minute has passed.
   For example, if it is 6:01:49 (that is, 49 seconds past one minute past 6 a.m.) and you set a cron job to run at 6:02, it does not execute. At 6:02, the cron daemon rereads its configuration files and sees the new job, but is not able to execute it. If you set the job to run at 6:02 a.m. every day, it is executed the following morning and every subsequent morning.
   This same situation exists when deleting jobs. If it is 6:01:49 and you have a job scheduled to run at 6:02, deleting the job makes no difference: cron runs it before it rereads the crontab files for changes. However, after it has reread the crontab file and noticed the job is no longer there, it is not executed on subsequent days.

Learning More About Your Shell

   All the shells listed in Table 11.1 have accompanying man pages, along with other documentation under the /usr/share/doc directory. Some of the documentation can be quite lengthy, but it is generally much better to have too much documentation than too little! The bash shell includes more than 100 pages in its manual, and the zsh shell documentation is so extensive that it includes the zshall meta man page (use man zshall to read this overview)!

Grokking grep

   If you plan to develop shell scripts to expand the capabilities of pattern-matching commands such as grep, you will benefit from learning more about using expressions. One of the definitive guides to using the pattern-matching capabilities of Unix and Linux commands is Mastering Regular Expressions by Jeffrey E. F. Freidl (O'Reilly), ISBN: 0-596-00289-0.

CAUTION

   Make sure that you read your command carefully when using wildcards; an all-too-common error is to type something like rm -rf * .txt with a space between the * and the .txt. By the time you wonder why the command is taking so long, bash will already have deleted most of your files. The problem is that it treats the * and the .txt separately. * matches everything, so bash deletes all your files.

Related Fedora and Linux Commands

   You can use these commands and tools when using the shell or writing shell scripts:
   ► chsh — Command used to change one's login shell
   ► kibitz — Allows two-person interaction with a single shell
   ► mc — A visual shell named the GNU Midnight Commander
   ► nano — An easy-to-use text editor for the console
   ► system-config-users — A graphical user-management utility that can be used to change one or more user login shells
   ► shar — Command used to create shell archives
   ► vi — The vi (actually vim) text editor

TIP

   A useful trick is to employ the watch command; it repeatedly reruns a command every 2 seconds by default. If you use
   # watch free
   you can see the output of the free command updated every 2 seconds.

A Case in Point

   A recent Harris poll of Fortune 500 executives found that roughly two-thirds of them had problems with their backups and disaster-recovery plans. How about you?

TIP

   To make a backup of a configuration file you are about to edit, use the cp command:
   $ cp filename filename.original
   And to restore it:
   $ cp filename.original filename
   Never edit or move the *.original file, or the original copy will be lost.

TIP

   If you are not willing or capable of assessing your backup needs and choosing a backup solution, a legion of consultants, hardware vendors, and software vendors would love to assist you. The best way to choose one in your area is to query other Unix and Linux system administrators (located through user groups, discussion groups, or mail lists) that are willing to share their experiences and make recommendations. If you cannot get a referral, ask the consultant for references and check them out.

Sound Practices

   You have to create your own best-backup plan, but here are some building blocks that should be incorporated into the foundation of any sound backup program:
   ► Maintain more than one copy of critical data.
   ► Label the backups.
   ► Store the backups in a climate-controlled and secure area.
   ► Use secure, offsite storage of critical data. Many companies choose bank vaults for their offsite storage, and this is highly recommended.
   ► Establish a backup policy that makes sense and can be followed religiously. Try to back up your data when the system is consistent (that is, no data is being written), which is usually overnight.
   ► Keep track of who has access to your backup media, and keep the total number of people as low as possible. If you can, allow only trusted personnel near your backups.
   ► Routinely verify backups and practice restoring data from them.
   ► Routinely inspect backup media for defects and regularly replace them (after destroying the data on them, if it is sensitive).

NOTE

   If you are a new sysadmin, you might be inheriting an existing backup strategy. Take some time to examine it and see whether it meets the current needs of the organization. Think about what backup protection your organization really needs, and determine whether the current strategy meets that need. If it does not, change the strategy. Consider whether users practice the current policy, and, if not, why it is not.

Backup Levels

   Unix uses the concept of backup levels as a shorthand way of referring to how much data is backed up in relation to a previous backup. It works this way:
   A level 0 backup is a full backup. The next backup level would be 1. Backups at the other numbered levels back up everything that has changed since the last backup at that level or a numerically higher level (the dump command, for example, offers 10 different backup levels). For example, a level 3 backup followed by a level 4 generates an incremental backup from the full backup, whereas a level 4 followed by a level 3 generates a differential backup between the two.

Simple Strategy

Full Backup on a Periodic Basis

Full Backups with Incremental Backups

Mirroring Data or RAID Arrays

FireWire Drives

CD-RW and DVD+RW/-RW Drives

TIP

   Older tape equipment is often available in the used equipment market and might be useful for smaller operations that have outgrown more limited backup device options.

CAUTION

   Neglecting to clean, align, and maintain tape drives puts your data at risk. The tapes themselves are also susceptible to mechanical wear and degradation. Hardware maintenance is part of a good backup policy. Do not ever forget that it is a question of when — not if — hardware will fail.

NOTE

   The software in a backup system must support the hardware, and this relationship can determine which hardware or software choices you make. Many sysadmins choose a particular backup software not because they prefer it to other options, but because it supports the hardware they own.
   The price seems right for free backup tools, but consider the software's ease of use and automation when assessing costs. If you must spend several hours implementing, debugging, documenting, and otherwise dealing with overly elaborate automation scripts, the real costs go up.

Creating Full and Incremental Backups with tar

NOTE

   The tar command can back up to a raw device (one with no file system) as well as a formatted partition. For example,
   # tar cvzf /dev/hdd /boot /etc /home
   backs up those directories to device /dev/hdd (not /dev/hda1, but to the unformatted device itself).
   The tar command can also back up over multiple floppy disks:
   # tar czvMf /dev/fd0 /home
   backs up the contents of /home and spreads the file out over multiple floppies, prompting you with this message:
   Prepare volume #2 for '/dev/fd0' and hit return:

Restoring Files from an Archive with tar

CAUTION

   File Roller does not complain if you select a compression format that is not supported by installed software until after you attempt to create the archive. Install any needed compression utilities first.

CAUTION

   Amanda does not support dump images larger than a single tape and requires a new tape for each run. If you forget to change a tape, Amanda continues to attempt backups until you insert a new tape, but those backups will not capture the data as you intended them to. Do not use too small a tape or forget to change a tape, or you will not be happy with the results.

Alternatives to the Fedora Rescue Disc

   The Fedora rescue disc might be inadequate for your system restoration needs; it might lack specific ethernet device support, file system support, or the kind of full utility functionality that you require for a successful recovery operation. An alternative exists in the SuperRescue CD created by H. Peter Anvin.
   Essentially, the SuperRescue CD is a reasonably full and robust Red Hat distribution (based on Red Hat 7.2 and the 2.4.20-rc1 kernel) that runs completely from a bootable CD. The best thing about the SuperRescue CD is that it comes with build scripts, so it is incredibly easy to add new software (that special driver or application) and create a new CD. The home page is at http://freshmeat.net/projects/superrescue/, but you can grab a copy directly at http://www.kernel.org/pub/dist/superrescue/v2/.

Relevant Fedora Commands

   The following commands are useful in performing backup, recovery, and restore operations in Fedora:
   ► amdump — Amanda is a network-based backup system, consisting of 18 separate commands, for use with Linux.
   ► ark — A KDE desktop GUI archiving utility.
   ► cp — The copy command.
   ► scp — The secure shell copy command.
   ► cpio — A data archive utility.
   ► dd — A data copy and conversion utility.
   ► gzip — The GNU compression utility.
   ► tar — The GNU tape archive utility.

NOTE

   The network configuration process described in this section is for client hosts. You cannot perform server network configuration, such as Domain Name System (DNS) and DHCP during installation. (See Chapter 23, "Managing DNS," for more information on configuring DNS; see the "DHCP" section later in this chapter for more information on that item.)

NOTE

   Bootp is the initial protocol on which DHCP was built, and it has mostly been replaced by DHCP.

/sbin/ifconfig

NOTE

   Promiscuous mode causes the NIC to receive all packets on the network. It is often used to sniff a network. Multicasting mode enables the NIC to receive all multicast traffic on the network.

/sbin/route

/bin/netstat

Adding Hosts to /etc/hosts

Service Settings in /etc/services

Using /etc/nsswitch.conf After Changing Naming Services

Setting a Name Server with /etc/resolv.conf

CAUTION

   If you make use of NetworkManager to handle your network connections, don't make any changes to /etc/resolv.conf, because it will cause havoc for NetworkManager. Instead, let NetworkManager dynamically work with this file of its own accord.

Setting DNS Search Order with /etc/host.conf

Examining Host Network Settings in /etc/sysconfig/network

NOTE

   Notice that zero is not included in Class A. The zero address is used for network-to-network broadcasts. Also, note that there are two other classes of networks, Classes D and E. Class D networks are reserved for multicast addresses and are not for use by network hosts. Class E addresses are deemed experimental, and thus are not open for public addressing.

Limits of Current IP Addressing

   The current IPv4 address scheme is based on 32-bit numbering and limits the number of available IP addresses to about 4.1 billion. Many companies and organizations (particularly in the United States) were assigned very large blocks of IP addresses in the early stages of the growth of the Internet, which has left a shortage of "open" addresses. Even with careful allocation of Internet-connected host IP addresses and the use of network address translation (NAT) to provide communication to and from machines behind an Internet-connected computer, the Internet might run out of available addresses.
   To solve this problem, a newer scheme named IPv6 (IP version 6) is being implemented. It uses a much larger addressing solution based on 128-bit addresses, with enough room to include much more information about a specific host or device, such as global positioning server (GPS) or serial numbering. Although the specific details about the entire contents of the an IPv6 address have yet to be finalized, all Internet- related organizations appear to agree that something must be done to provide more addresses. It's difficult to gauge just how big the Internet actually is, but according to Internet World Stats, some 1.224 billion people use the Internet as of September 2007. Multiply that by the number of mail servers, newsgroup servers and other web servers that are attached to the web and you will quickly find that the range of addresses supplied by IPv4 is quickly running out.
   You can get a good overview of the differences between IPv4 and IPv6 policies regarding IP address assignments, and the registration process of obtaining IP addresses, by browsing to http://www.arin.net/library/index.html. Read the Linux IPv6 HOWTO by browsing tohttp://tldp.org/HOWTO/Linux+IPv6-HOWTO/.
   Fedora supports the use of IPv6 and includes a number of networking tools conforming to IPv6 addressing. You can configure support for IPv6 by using settings and options in the file named network under the /etc/sysconfig directory, along with making changes to related network configuration files, such as /etc/hosts. Many IPv6-based tools, such as ipcalc6, ping6, and traceroute6, are available for Fedora. See various files under the /usr/share/doc/initscripts directory for more information specific to setting up IPv6 addressing with Linux and Fedora. Migration to IPv6 is slow in coming, however, because the majority of computer operating systems, software, hardware, firmware, and users are still in the IPv4 mindset. Supporting IPv6 will require rewrites to many networking utilities, portions of operating systems currently in use, and firmware in routing and firewall hardware.

NOTE

   You can learn more about DHCP by reading RFC 2131, "Dynamic Host Configuration Protocol." Browse tohttp://www.ietf.org/rfc/rfc2131.txt.

NOTE

   The problem of using DHCP to configure servers that make use of registered host- names is being addressed by Dynamic DNS which, when fully developed, will enable DHCP to register IP addresses with DNS. This will allow you, for example, to register a domain name (such as imalinuxuser.com) and be able to easily access that domain's web server without needing to use static IP addressing of a specific host. The largest hurdle to overcome is the security implication of enabling each host connecting to the system to update DNS. A few companies, such as DynDNS (http://www.dyndns.com/), are already offering Dynamic DNS services and have clients for Linux.

DHCP dhclient

DHCP Server

NOTE

   For whichever installation method you choose, be sure that a file called /etc/dhcpd.leases is created. The file can be empty, but it does need to exist for dhcpd to start properly.

DHCP Server Configuration

NOTE

   The dhcpd.conf file requires semicolons (;) after each command statement. If your configuration file has errors or runs improperly, check for this.

CAUTION

   Remember, only one DHCP server should exist on a local network to avoid problems. Your DHCP might not work correctly on a LAN with hosts running outdated legacy operating systems. Often Windows NT servers have the Windows DHCP server installed by default. Because there is no configuration file for NT to sort through, that DHCP server configures your host before the Linux server if both machines are on the same LAN. Check your Windows NT servers for this situation and disable DHCP on the Windows NT server; afterward, your other DHCP-enabled hosts should configure correctly. Also, check to make sure that there are no conflicts if you use a cable or DSL modem, wire less access point (WAP), or other intelligent router on your LAN that can provide DHCP

NOTE

   Do not rely on a single point of protection for your LAN, especially if you use wireless networking, provide dial-in services, or allow mobile (laptop or PDA) users internal or external access to your network. Companies, institutions, and individuals relying on a "moat mentality" have often discovered to their dismay that such an approach to security is easily breached. Make sure that your network operation is accompanied by a security policy that stresses multiple levels of secure access, with protection built in to every server and workstation — something easily accomplished with Linux.

NOTE

   Most IP addresses are dynamically assigned by ISPs; ISPs have a pool of addresses, and you get whatever address is available. From the ISP's viewpoint, a small number of addresses can serve a large number of people because not everyone will be online at the same time. For most Internet services, a dynamic IP works well because it is the ISP's job to route that information to you, and it sits in the middle —between you and the service you want to use. But a dynamic IP address changes, and if someone needs to find you at the same address (if you run a website or a file transfer site, for example), an IP that changes every time you log on will not work well. For that, you need a static IP. Because your ISP cannot reuse that IP with its other customers, it will likely charge you more for a static IP than a dynamic If? The average consumer doesn't need the benefit of a static IP so he is happy paying less for a dynamically assigned IP Also, the DNS information can be provided automatically by the ISP by the DHCP

NOTE

   The information in this book will help you understand and avoid many connection issues, but you might experience connection problems. Keep the telephone number of the technical help service for your ISP on hand in case you are not able to establish a connection. But be aware that few ISPs offer Linux support, and you might need to seek help from a Linux-savvy friend or a Linux user's group if your special circumstances cannot be handled from the knowledge you gain from this book. Of course, the best place to look is on the Internet. Use Google's Linux page (http://www.google.com/linux) to research the problem and see whether any other users have found fixes or workarounds.

NOTE

   DSL service is an "always-on" type of Internet service, although you can turn off the connection under Fedora by using the Network Device Control, found under System, Administration. An always-on connection exposes your computer to malicious abuse from crackers who trawl the Internet attempting to gain access to other computer systems. In addition to the capability to turn off such connections, Fedora provides a firewall to keep crackers out; you configured a simple firewall during the original installation. The firewall can also be configured from the Security Level Configuration tool found in the System Settings menu selection as Security Level.

NOTE

   You can check to see whether PPP is installed on your system by running the pppd command as root from a command line with the --help argument, like this:
   # pppd --help
   That will list the current version number and describe a few available options if PPP is installed.
   If PPP isn't installed on your system, use the rpm command to install the PPP package from the Fedora DVD or use the Packages menu item from the System Settings menu. Chapter 34, "Advanced Software Management," covers the details of using rpm and the graphical package manager.

CAUTION

   Many software modems do not work with Linux because the manufacturers won't release programming information about them or provide Linux drivers. An external serial port modem or ISA bus modem almost always works; USB and PCI modems are still problematic. It is suggested that you do a thorough Google search, using your modem's name and model number, to see how others have solved problems with that particular modem. Links to software modem compatibility sites appear at the end of this chapter.

CAUTION

   You can use /dev/modem only if Fedora's kudzu utility has recognized and configured the computer's modem. (If /dev/modem does not exist, use the ln command to create the file as a symbolic link pointing to the correct serial port.) To create the symlink (from /dev/ttyS2, for example):
   # ln -s /dev/ttyS2 /dev/modem
   If your modem was not automatically detected and the /dev/modem link configured, it is possible that you have a software modem, also known as a Winmodem or HSF modem (refer to the earlier note).

TIP

   If your modem is installed and working, you can access it with a terminal program such as minicom, which usually is not installed by default. After you install it using yum or from source code, start it the first time with the -s argument to configure it:
   $ minicom -s
   Set the serial port to that of your modem, and then save the configuration. You can then use minicom to communicate with your modem by using the AT command to set and see its responses.
   If you do not want to go to that trouble, you can use the echo command to send commands to the modem, but the modem won't be capable of responding to you. For example, the AT&W command can be sent as follows:
   # echo "AT&W" > /dev/modem