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Keyboard section Sets keyboard settings, including the layout of the keyboard and how certain key sequences are mapped to the keyboard. Pointer section Selects the pointer you are using (typically a mouse linked to /dev/mouse). Also sets speed and button emulation, when appropriate. Monitor section Sets the type of monitor, along with its horizontal sync rate, vertical refresh rate, and settings needed to operate at different resolutions. Screen section Binds together the graphics board and monitor information to be referenced later by the ServerLayout section. Graphics device section Identifies your video card and, optionally, video RAM and clock information for the chipset. ServerLayout section Sets server definitions for different X servers (if necessary). For further information on the XF86Config file, see the XF86Config man pages (type man XF86Config). Getting more information If you tried configuring X and you still have a server that crashes or has a garbled display, your video card may either be unsupported or may require special configuration. Here are several locations you can check for further information: XFree86.org (http://www.xfree86.org/) The latest information about the X servers that come with Red Hat Linux is available from the XFree86.org Web site. XFree86 is the freeware version of X used with all major Linux distributions. Red Hat Support (www.redhat.com/support) Search the Red Hat support database for the model of your card. There may already be reports of problems (and hopefully fixes) related to your card. X documentation README files that are specific to different types of video cards are delivered with XFree86. Look in the XFree86 doc directory (/usr/X11R6/lib/X11/doc) for a README file specific to the type of video card (or more specifically, the video chip set) you are using. Starting the X Desktop There are several different ways you can start your desktop in Red Hat Linux. If Red Hat Linux starts up and you see a graphical login screen, you can just log in and your desktop environment should appear. If Red Hat Linux starts up to a simple text-based login prompt, you can have the desktop environment start after you log in (either manually or automatically). Each of these methods is described in this section. Cross-Reference Procedures in this chapter assume that you have already configured your monitor and
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monitor. Check the manual that comes with your monitor for that information. 5. Select how much memory is on your video card, highlight OK, and press Enter. The next window asks you to identify your clock configuration. 6. Select No Clockchip Setting (unless you know that your card requires a special clockchip setting). Highlight Ok and press Enter. The next window displays video modes that are available to your video card. 7. Select the number of colors and video resolutions for each number of colors. A higher number of colors (8-bit, 16-bit, or 24-bit) allow better quality graphics, but can slow performance. Higher resolutions (800 @@ts 600, 1024 @@ts 768, or 1152 @@ts 864) allow more space for windows, but everything is smaller. You can select several resolutions for each set of colors. Position the cursor over a selection and press the space bar to select it. Highlight Ok and press Enter to continue. The window warns you that it is about to test X. 8. Highlight Ok and press Enter. If X is working properly, you should see a pop-up window that asks if you can see it. If you don t see this window, it will timeout after a few seconds and return to your Xconfigurator. You ll need to try configuring the card again. If you do see the pop-up window, click the Yes button. You are asked if you want to start X at boot-time. 9. Click Yes (to have X start when you boot your computer) or No (to start from a text-based prompt and start X later manually). A pop-up window alerts you that the new configuration has been saved. 10. Click OK and you are done. You should now be able to start your X environment. The next section describes the XF86Config file. Note If your GUI is still not working, go to http://www.xfree86.org/ and click the Driver Status Document link for your version of XFree86 (probably version 4.1). Find the manufacturer of your video card (or at least of the chip set in your video card) and select that link to find out if your card is supported or if a workaround is needed. Understanding the XF86Config file The XF86Config file (located in the /etc/X11 directory) contains definitions used by the X server to use your video card, keyboard, mouse, and monitor. In general, novice users should not edit this file directly, but rather, use Xconfigurator to change its contents. For some video cards, however, there is a need for some manual configuration to get the card working properly. The following is a description of the basic information contained in the XF86Config file: Files section Sets the locations of the RGB (color) and fonts databases. Server flags section Allows you to disable abort and mode switching key sequences (usually you will leave this section alone).
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Chapter 4: Working with the Desktop Add a graphical user interface (GUI) to an otherwise unintuitive operating system, and it immediately becomes something anyone can use. Icons can represent programs and files. Clicking a mouse button can start applications. In keeping with other UNIX-like systems, Linux uses the X Window System (also referred to as X11 or just X) as the framework for its graphical desktop. On top of this framework, Red Hat Linux lets you choose either (or both) of two powerful desktop environments: GNOME and KDE. This chapter describes how to get your X environment working, start up the desktop, and use the GNOME and KDE desktop environments. It also describes a variety of X features you can use to manipulate the desktop. Configuring Your Desktop If you installed Red Hat Linux as a desktop system and everything went smoothly, you should have configured your video card and chosen a desktop environment (GNOME or KDE). If so, you can skip ahead to the Starting the X Desktop section. If you were unable to configure your desktop or if you need to change it (for example, you may have added a video card or changed your monitor), this section is here for your reference. If Red Hat Linux has been successfully installed (along with the desired desktop environment) but the GUI wasn’t configured properly, you will only see a simple text-based login prompt when you start Red Hat Linux. This login prompt may look something like this: Red Hat Linux release 7.2 Kernel 2.4 on an i686 YourComputer login: Log in as the root user. Because there is no graphical desktop interface set up yet, you need to do some work from the shell command line. First, try the Xconfigurator command. Running Xconfigurator The Xconfigurator command can be used to set up the links and configuration files needed to run your graphical X desktop environment. It checks that the correct X server is installed and configures the /etc/X11/XF86Config file. The following is an example of an Xconfigurator session: 1. Type Xconfigurator from the shell prompt (as the root user). A welcome screen appears. 2. Highlight the Ok button (using tab and arrow keys) and press Enter. Xconfigurator probes for your video card. If it finds one, it displays the name of the card, the X server, and the Xfree4 driver. 3. Highlight Ok and press Enter to continue. A list of monitors appears. 4. Select the type of monitor you are using. You can use Page Up and Page Down to search through the list. Type a letter to go directly to a monitor name that begins with that letter. Highlight the correct monitor, highlight Ok, and press Enter. The next window asks you to identify your video memory. Note If your monitor is not on the list, select Custom. To install a custom monitor, you need to determine the vertical refresh rate and the horizontal sync rate to properly configure your
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:g/Local/s//Remote/gp Substitutes every occurrence of the word Local with the word Remote in the entire file, then prints each line so that you can see the changes (piping it through more if output fills more than one page). Using numbers with commands You can precede most vi commands with numbers to have the command repeated that number of times. This is a handy way to deal with several lines, words, or characters at a time. Here are some examples: 3dw Deletes the next three words. 5cl Changes the next five letters (that is, removes the letters and goes into input mode). 12j Moves down 12 lines. Putting a number in front of most commands just repeats those commands. At this point, you should be fairly proficient at using the vi command. Summary Working from a shell command-line interpreter within Red Hat Linux may not be as simple as using a GUI, but it offers many powerful and flexible features. This chapter describes how to log in to Red Hat Linux and work with shell commands. Features for running commands include recalling commands from a history list, completing commands, and joining commands in various ways. This chapter describes how shell environment variables can be used to store and recall important pieces of information. It also teaches you to modify shell configuration files to tailor the shell to suit your needs. Finally, the chapter describes how to use the Red Hat Linux file system to create files and directories, understand permissions, and work with files (moving, copying, and removing them).
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Ctrl+d Page ahead 1/2 page at a time. Ctrl+u Page back 1/2 page at a time. G Go to the last line of the file. 1G Go to the first line of the file. (Instead of 1, you could use any number to go to that line number in the file.) Searching for text To search for the next occurrence of text in the file, use either the slash (/) or the question mark (?) character. Within the search, you can also use metacharacters. Here are some examples: /hello Searches forward for the word hello. ?goodbye Searches backwards for the word goodbye. /The*foot Searches forward for a line that has the word The in it and also, after that at some point, the word foot. ?[pP]rint Searches backward for either the word print or Print. Remember that case does matter in Linux, so using brackets is one way to search for words that could have different capitalization: The vi editor was originally based on the ex editor. That editor did not let you work in full-screen mode. However, it did enable you to run commands that let you find and change text on one or more lines at a time. When you type a colon and the cursor goes to the bottom of the screen, you are essentially in ex mode. Here is an example of some of those ex commands for searching for and changing text. (I chose the words Local and Remote to search for, but you can use any appropriate words.) :g/Local Searches for the word Local and prints every occurrence of that line from the file. (If there is more than a screen full, the output is piped to the more command.) :s/Local/Remote Substitutes the word Remote for the word Local on the current line. :g/Local/s//Remote Substitutes the first occurrence of the word Local on every line of the file with the word Remote. :g/Local/s//Remote/g Substitutes every occurrence of the word Local with the word Remote in the entire file.
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If you ve really trashed the file by mistake, the :q! command is the best way to exit and abandon your changes. The file reverts to the most recently changed version. So, if you just did a :w, you are stuck with the changes up to that point. If you just want to undo a few bad edits, press u to back out of changes. You have learned a handful of vi editing commands. I describe many, many more commands in the following sections. However, before I do, here are a few tips to smooth out your first trials with vi: Esc Remember that Esc gets you back to command mode. (I ve watched people press every key on the keyboard trying to get out of a file.) Esc followed by ZZ gets you out of command mode, saves the file, and exits. u Press u to undo the previous change you made. Continue to press u to undo the change before that, and the one before that. Ctrl-r If you decide you didn t want to undo the previous command, use Ctrl-r for Redo. Essentially, this command undoes your undo. Caps Lock Beware of hitting the Caps Lock by mistake. Everything you type in vi has a different meaning when the letters are capitalized. You don t get a warning that you are typing capitals things just start acting weird. :! command You can run a command while you are in vi using :! followed by a command name. For example, type :!date to see the current date and time, type :!pwd to see what your current directory is, or type :!jobs to see if you have any jobs running in the background. When the command completes, press Enter and you are back to editing the file. You could even do that with a shell (:!bash) to run a few commands from the shell, then type exit to return to vi. (I recommend doing a save before escaping to the shell, just in case you forget to go back to vi.) — INSERT — When you are in insert mode, the word INSERT appears at the bottom of the screen. Other messages also appear at the line at the bottom of the screen. Ctrl+g If you forget what you are editing, pressing these keys prints the name of the file that you are editing and the current line that you are on. It also prints the total number of lines in the file, the percentage of how far you are through the file, and the column number the cursor is on. This just helps you get your bearings. Moving around the file Besides the few movement commands described earlier, there are other ways of moving around a vi file. To try these out, you may want to open a large file that you can t do much damage to. (How about copying /var/log/messages to /tmp?) Here are some possibilities: Ctrl+f Page ahead, one page at a time. Ctrl+b Page back, one page at a time.
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b Moves the cursor to the beginning of the previous word. 0 (zero) Moves the cursor to the beginning of the current line. $ Moves the cursor to the end of the current line. H Moves the cursor to the upper-left corner of the screen (first line on the screen). M Moves the cursor to the first character of the middle line on the screen. L Moves the cursor to the lower-left corner of the screen (last line on the screen). Now that you know how to input text and move around in text, the only other editing you need to know is how to delete text. Here are a few vi commands for deleting text: x Deletes the character under the cursor. X Deletes the character directly before the cursor. dw Deletes from the current character to the end of the current word. d$ Deletes from the current character to the end of the current line. d0 Deletes from the previous character to the beginning of the current line. If you feel pretty good about creating text and moving around the file, you may want to wrap things up. Several keystrokes for saving and quitting the file follow: ZZ Save the current changes to the file and exit from vi. :w Save the current file but continue editing. :wq Same as ZZ. :q Quit the current file. This works only if you don t have any unsaved changes. :q! Quit the current file and DON T save the changes you just made to the file. Tip
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emacs, instead of a graphical editor, is that you can use it from a Terminal window, a character terminal, or a character-based connection over a network (using telnet or ssh, for example). No GUI is required. This section provides a brief tutorial of the vi text editor. Any time in this book that I suggest you manually edit a configuration file, you can use vi to do that editing (from any shell prompt). The vi editor is difficult to learn at first. But when you know it, you will be able to edit and move files around quickly and efficiently. Your fingers never have to leave the keyboard to pick up a mouse or hit a function key. Starting with vi Most often, you start vi to open a particular file. For example, to open a file called /tmp/test, type the following command: $ vi /tmp/test If this is a new file, you should see something similar to the following: ~ ~ ~ ~ ~ “/tmp/test” [New File] The box at the top represents where your cursor is. The bottom line keeps you informed about what is going on with your editing (here you just opened a new file). In between, there are tildes (~) as filler because there is no text in the file yet. Now here s the intimidating part: there are no hints, menus, or icons to tell you what to do. On top of that, you can t just start typing. If you do, the computer is likely to beep at you. The first things you need to know are the different operating modes. The vi editor operates in either command mode or input mode. When you start vi, you are in command mode. Before you can add or change text in the file, you have to type a command to tell vi what you want to do. A command consists of one or two letters and an optional number. To get into input mode, you need to type an input command. To start out, type either of the following input commands: a Add. After you type a, you can input text that starts to the right of the cursor. i Insert. After you type i, you can input text that starts to the left of the cursor. Type a few words and press Enter. Repeat that a few times until you have a few lines of text. When you are done typing, press Esc. You are now back in command mode. Remember the Esc key! It always places you back into command mode. Now that you have a file with some text in it, try moving around within that text with the following keys or letters: Arrow keys Use the arrow keys to move up, down, left, or right in the file one character at a time. To move left and right you can also use Backspace and the spacebar, respectively. If you prefer to keep your fingers on the keyboard, use h (left), l (right), j (down), or k (up) to move the cursor. w Moves the cursor to the beginning of the next word.
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chmod 755 files rwxr-xr-x chmod 644 files rw–r -r– chmod 000 files ——— When you try to create a file, by default it is given the permission: rw-r–r–. A directory is given the permission rwxr-xr-x. These default values are determined by the value of umask. Type umask to see what your umask value is. For example: $ umask Subtract the number you see in each of the three sets from seven and you will see the value of each of the fields. The umask of 022 results in permission for a directory of 755 (rwxr-xr-x). That same umask results in a file permission of 644 (rw-r–r–). (Execute permissions are off by default for regular files.) Tip Here s a great tip for changing the permission for lots of files at once. Using the -R options of chmod, you could change the permission for all of the files and directories within a directory structure at once. For example, if you wanted to open permissions completely to all files and directories in the /tmp/test directory, you could type the following: $ chmod -R 777 /tmp/test This command line runs chmod recursively (-R) for the /tmp/test directory, as well as any files or directories that exist below that point in the file system (for example, /tmp/test/hat, /tmp/test/hat/baseballcaps, and so on). All would be set to 777 (full read/write/execute permissions). Caution The -R option of chmod works best if you are opening permissions completely or adding execute permission (as well as the appropriate read/write permission). The reason is that if you turn off execute permission recursively, you close off your ability to change to any directory in that structure. For example, chmod -R 644 /tmp/test turns off execute permission for the /tmp/test directory, then fails to change any files or directories below that point. Moving, copying, and deleting files Commands for moving, copying, and deleting files are fairly straightforward. To change the location of a file, use the mv command. To copy a file from one location to another, use the cp command. To remove a file, use the rm command. Here are some examples: $ mv abc def $ mv abc ~ $ cp abc def $ cp abc ~ $ rm abc $ rm * Of the two move (mv) commands, the first moves the file abc to the file def in the same directory (essentially renaming it), whereas the second moves the file abc to your home directory (~). The first copy command (cp) copies abc to the file def, whereas the second copies abc to you home directory (~). The first remove command (rm) deletes the abc file, whereas the second removes all the files in the current directory. Note For the root user, the mv, cp, and rm commands are aliased to each be run with the -i option. This causes a prompt to appear asking you to confirm each move, copy, and removal, one file at a time. This is done to prevent the root user from messing up a large group of files by mistake. Using the vi Text Editor It s almost impossible to use Red Hat Linux for any period of time and not need to use a text editor. If you are using a GUI, you can run xedit, which has a fairly intuitive interface for editing text. Most Red Hat Linux shell users will use either the vi or emacs commands to edit plain-text files. The advantage of using vi or
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< Direct the contents of a file to the command. > Direct the output of a command to a file, deleting the existing file. >> Direct the output of a command to a command, adding the output to the end of the existing file. Here are some examples of command lines where information is directed to and from files: $ mail root < ~/.bashrc $ nroff -man /usr/share/man/man1/chmod.1* > /tmp/chmod $ echo “I finished the project on $(date)” > ~/projects In the first example, the contents of the .bashrc file in the home directory are sent in a mail message to the computer s root user. The second command line formats the chmod man page (using the nroff command) and sends the output to the file /tmp/chmod (erasing the previous /tmp/chmod file, if it existed). The final command results in the following text being added to the user s project file: I finished the project on Sun Nov 25 13:46:49 PST 2001 Understanding file permissions After you ve worked with Linux for a while, you are almost sure to get a Permission Denied message. Permissions associated with files and directories in Linux were designed to keep users from accessing other users private files and to protect important system files. The nine bits assigned to each file for permissions define the access that you and others have to your file. Permission bits appear as rwxrwxrwx. The first three bits apply to the owner s permission, the next three apply to the owner s group, and the last three apply to all others. The r stands for read, the w stands for write, and the x stands for execute permissions. If a dash appears instead of the letter, it means that permission is turned off for that associated read, write, or execute. You can see the permission for any file or directory by typing the ls -ld command. The named file or directory appears as those shown in the example below: $ ls -ld ch3 test -rw-rw-r– 1 chris sales 4983 Jan 18 22:13 ch3 drwxr-xr-x 2 chris sales 1024 Jan 24 13:47 test The first line shows a file (ch3) that has read and write on for the owner and the group. All other users have read permission, which means they can view the file but cannot change its contents or remove it. The second line shows a directory (indicated by the letter d before the permission bits). The owner has read, write, and execute permission, while the group and other users have only read and execute permissions. As a result, only the owner can add, change, or delete files in that directory. Any other user, however, can only read the contents, change to that directory, and list the contents of the directory. If you own a file, you can change the permission on it as you please. You can do this with the chmod command. For each of the three sets of permission on a file (read, write, and execute), the r is assigned to the number 4, w to 2, and x to 1. So to make permissions wide open for yourself as owner, you would set the first number to 7 (4 plus 2 plus 1). The same would be true for group and other permission. Any combination of permissions can result from 0 (no permission) through 7 (full permission). Here are some examples of how to change permission on a file and what the resulting permission would be: chmod 777 files rwxrwxrwx
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