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Part II: Using Red Hat Linux Chapter List Chapter 3: Getting to Know Red Hat Linux Chapter 4: Working with the Desktop Chapter 5: Accessing and Running Applications Chapter 6: Publishing with Red Hat Linux Chapter 7: Playing Games with Red Hat Linux Chapter 8: Multimedia in Red Hat Linux Chapter 9: Tools for Using the Internet and the Web
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Summary Installing Linux is not nearly the adventure it once was. Precompiled binary software and preselected packaging and partitions can make most Red Hat Linux installations a simple proposition. This type of installation has made entering the Linux arena more possible for computer users who are not programmers. Besides providing some step-by-step installation procedures, this chapter discussed some of the trickier aspects of Red Hat Linux installation. In particular, ways of partitioning your hard disk, creating installation boot disks, and changing the boot procedure were described. The chapter also discussed how to reconfigure and install a new kernel.
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piece of hardware isn’t working, you can check here to make sure that the kernel found the hardware and configured it properly. /var/log/boot.log This file contains information about each service that is started up at boot time. You can see if each service started successfully. If a service fails to start properly, there may be clues in this file that will help you learn what went wrong. If something was set wrong (such as your mouse) or just isn’t working quite right (such as your video display), you can always go back after Red Hat Linux is running and correct the problem. Here is a list of utilities you can use to reconfigure different features that were set during installation: Changing or adding a mouse: mouseconfig Adding or deleting software packages: gnorpm or rpm Partitioning: fdisk or cfdisk Boot loader: /boot/grub/grub.conf (for GRUB); lilo and /etc/lilo.conf (for LILO) Networking (Ethernet & TCP/IP): neat Time zone: timeconfig User accounts: useradd or linuxconf X Window System: Xconfigurator Here are a few other random tips that can help you during installation: If installation fails because the installation procedure is unable to detect your video card, try restarting installation in text mode. After Red Hat Linux is installed and running, use the Xconfigurator command to configure your video card and monitor. If your mouse is not detected during installation, you can use arrow keys and the Tab key to make selections. Probably the best resource for troubleshooting your installation problems is the Red Hat Support site (www.redhat.com/apps/support). Links from that page can take you to documentation, updates and errata, and information about support programs. If you are having problems with a particular piece of hardware, try searching the Solutions Database, using the name of the hardware in the search box. If you are having problems with particular hardware, chances are someone else did too.
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Making modules Modules that are not compiled into the kernel can be compiled as loadable modules using the modules option. Once the modules are compiled, you can install them in /lib/modules/kernel (where kernel is replaced by the number representing the current kernel) with the modules_install option. Here is what you need to type: # make modules # make modules_install To add a module when your system is running, you could use the modprobe or insmod commands. Creating an initrd image If your computer does not have a SCSI adapter, skip this step. However, if your computer does have a SCSI adapter and needs to load the SCSI module at boot time, you need to create an initrd image. First, check that your /etc/modules.conf file contains a line for your SCSI adapter. For example: alias scsi_hostadapter aic7xxx Next, use the mkinitrd command to build the new image. The mkinitrd command takes two options. The first option indicates the name of the new image. The second indicates the kernel from which the modules are taken (such as /lib/modules/2.4.7-10). For example: # mkinitrd /boot/newinitrd-image 2.4.7-10 When you create an entry for this new kernel in /etc/lilo.conf, make sure you add the new initrd image to that entry. For example: initrd=/boot/newinitrd-image Installing the new kernel To install the new kernel files in their proper places, type the following: # make install The most common way to install the new kernel is to set it up to boot by LILO. You can do that either by replacing the old boot image with the new one (which is a bit risky until you know that the new one is working) or by adding the new one as an alternative bootable image. Ways of setting up boot images in the GRUB or LILO boot loader are described in the GRUB and LILO sections, respectively, earlier in this chapter. Troubleshooting Your Installation After you have finished installing Red Hat Linux, you can check how the installation went by checking your log files. There are three places to look once the system comes up: /tmp/upgrade.log When upgrading packages, output from each installed package is sent to this file. You can see what packages were installed and if any of them failed. /var/log/dmesg This file contains the messages that are sent to the console terminal as the system boots up, including messages relating to the kernel being started and hardware being recognized. If a
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This prepares you to create the new kernel configuration. It thoroughly cleans up the kernel configuration directories. Making the configuration To choose the kernel options that you want, you must run make with the config, menuconfig, or xconfig options. By far, the easiest option is xconfig, though it requires that you run an X desktop (such as GNOME or KDE). Here is an example: # make xconfig If you are not running X, you can use config or menuconfig. Using make config presents you with a pure text-based, question-and-answer way of rebuilding your kernel. Typing make menuconfig from /usr/src/linux* provides a menu-driven interface (which runs in a character terminal). Besides being a bit nicer to look at, the menuconfig and xconfig kernel configuration tools enable you to select only those areas of the kernel that you want to change. With make config, you have to step through each category. With the xconfig tool, you see all selections available in a category, though if a category is turned off, selections within that category are grayed out. Also, if you make a mistake, just select the category again. Checking for dependencies When you are done configuring the kernel, save the changes. After you have made the kernel configuration changes that you want, you have to go back to the /usr/src/linux* directory and type the following: # make dep The make dep command checks that dependencies of the packages are met. Next you need to prepare the source tree. Preparing the source tree To prepare the source tree for the new kernel build, run the make clean command as follows: # make clean Compiling the new kernel You have several choices for compiling the new kernel. You can create the new kernel boot image so that it is stored on your hard disk or have a copy placed on floppy disk. The latter is good for testing the new kernel. You can boot the image from floppy before you install it. So, if the new kernel doesn’t work, you can simply not install it. To compile the kernel and save it to a floppy disk (as well as to the hard disk), place a floppy disk in the disk drive and run: make zdisk. The other option results in saving the new image only to hard disk. To do that, type make zImage to compile the kernel. If the image created by make zImage is too large, type the following to create a more compressed image: # make bzImage This process takes a while, so be patient. In any case, the image is placed in the arch/i386/boot directory. The resulting file is a compressed boot image.
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disk drives. QoS and/or fair queuing If your network devices include some real-time devices that require a minimum quality of service (QoS), you can change some of these QoS values to favor certain interfaces when there is a lot of demand for service. Turning on QoS lets you try any of a handful of different algorithms. As you read this and other documents that describe how to use Red Hat Linux, the documents may describe features that require changing the kernel for those features to work. By using tools such as the X kernel configuration tool, you can determine which features are turned on and off by default, and build a kernel to suit your needs. Note If you need to support a hardware device that is only added temporarily or occasionally to your computer, you should try to configure it as a loadable module. In that way, you can load and unload the module as needed, without making the kernel bear any performance penalty when the device is not needed. Installing kernel source code To reconfigure the kernel, you need the Linux source code. You can install that source code from the second Red Hat Linux installation CD that comes with this book (CD-2). If the source code is already installed on your Linux system, it should be in the /usr/src/linux* directory (for example, /usr/src/linux-2.4). The kernel source code is contained in the kernel-source package in RedHat/RPMS directory on the second installation CD. When I checked the disk space, the source code consumed about 114MB of disk space in /usr/src/linux-2.4 (which is a link to a directory that has a name reflecting the kernel release, such as linux-2.4.7-10). To install the kernel source code from the RPMS directory, type: # rpm -i kernel-source* Starting to reconfigure the kernel The steps for reconfiguring your kernel include configuring the options, checking for dependencies, cleaning up the files, and compiling the new kernel. Each of these steps is fairly straightforward and described in the text that follows: Protect your system During Red Hat Linux installation, you should have created an emergency boot disk. This floppy disk allows you to boot your Linux system in case the new kernel doesn’t boot or in case your grub.conf file doesn t work (so that the boot loader fails). If you did not create one, or if you can’t find it, insert a blank floppy disk in the first floppy drive and type the following: # mkbootdisk –device /dev/fd0 2.4.7-10 Replace the number 2.4.7-10 with the version number of your kernel. Press Enter to continue, as prompted. Setting up the configuration To begin reconfiguring the kernel, you should be in a bash shell. (If you are not sure, type bash at the command line.) Then go to the /usr/src/linux* directory and type: # make mrproper
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You need to know the device on which you want to install GRUB. For example, to install GRUB on the master boot record of the first disk, type the following as root user from a Terminal window: # grub-install /dev/hda The new Master Boot Record is written to boot with the GRUB boot loader. 3. Reboot your computer. You should see the GRUB boot screen. Reconfiguring the kernel When you install Red Hat Linux, the kernel (which represents the core of the operating system) is automatically configured for you and ready to run. Many assumptions are built into this kernel, including the types of drivers that you will need to run your hardware and the services that the kernel provides. There are times when you may want to change these assumptions. To do that, you can reconfigure your kernel. Note Not all changes to the features in your kernel require that you rebuild it. Many drivers are available to an installed Red Hat Linux system in the form of loadable modules. Loadable modules can be used to add features to a running kernel. For example, the PCMCIA feature uses loadable modules. You can use the insmod and modprobe commands to load modules that you need. Reconfiguring your kernel is a tedious job. It consists of answering a lot of questions (some of which you will have no idea how to answer). In most cases, the kernel configuration process has defaults set up. So, if you run into a question you can’t answer, press Enter to use the default. Kernel configuration also takes time. The Kernel-HOWTO suggests that the process can take from 20 to 90 minutes, depending on hardware. To simplify the process of reconfiguring your kernel, the xconfig option to make for rebuilding the kernel offers a graphical interface. Using make xconfig, you can focus on the drivers you want to add and remove, instead of having to page through all the drivers. Deciding to reconfigure the kernel There are times when you need to reconfigure the kernel for it to work the way you need it to. A lot of the features that are turned off by default are off either because they relate to experimental features or because they are needed to supports bugs (or limited features) in some older computer hardware. Here are a few examples: Processor type and features If you are using any 386 CPU or a 486 CPU with no math coprocessor, you must turn off the math emulation value in the kernel. Also, you can have your kernel more specifically tuned to your processor by choosing 386, 486/Cx486, 586/K5/5×86/6×86, Pentium/K6/TSC, or PPro/6×86MX (depending on the CPU in your computer). Networking options Network should be on by default. It should be on even if you are not connected to a network because the X Window system (your graphical desktop) relies on it. Otherwise, you will want to reconfigure networking options if Linux is operating as a router and you want to optimize it as such (by default, it is optimized to act as a host). Certain experimental options (X.25, SPX, and others) are also turned off by default. Block devices For some older disk drives, you may need to use an old disk-only driver on the primary interface. With that selected, you won’t be able to have an IDE/ATAPI CD-ROM attached to the primary IDE interface. However, turning on the disk-only driver may be necessary for some older
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defined in the label option. password=password You can password-protect the image by adding a password option line and replacing password your own password. The password would have to be entered to boot the image. restricted This option is used with the password option. It indicates that a password should be used only if command-line options are given when trying to boot the image. For Linux kernel images, there are specific options that you can use. These options let you deal with hardware issues that can’t be auto-detected, or provide information such as how the root file system is mounted. Here are some of kernel image specific options: append Add a string of letters and numbers to this option that need to be passed to the kernel. In particular, these can be parameters that need to be passed to better define the hard disk when some aspect of that disk can’t be autodetected. ramdisk Add the size of the RAM disk that you want to use so as to override the size of the RAM disk built into the kernel. read-only Indicates to mount the root file system read-only. It is typically remounted read-write after the disk is checked. read-write Indicates to mount the root file system read/write. Changing your boot loader If you don’t want to use the GRUB boot loader, or if you tried out LILO and want to switch back to GRUB, it’s not hard to change to a different boot loader. To switch your boot loader from GRUB to LILO, do the following: 1. Configure the /etc/lilo.conf file as described in the “Booting your computer with LILO” section. 2. As root user from a Terminal window, type the following: # lilo The new Master Boot Record is written, including the entries in /etc/lilo.conf. 3. Reboot your computer. You should see the LILO boot screen. To change your boot loader from LILO to GRUB, do the following: 1. Configure the /boot/grub/grub.conf file as described in the “Booting your computer with GRUB” section. 2.
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Add several lines to the /etc/lilo.conf file so that the image can be started at boot time if it is selected. For example: image=/boot/zImage-2.4.7-10 label=new 3. Type the lilo -t command (as root user) to test that the changes were okay. 4. Type the lilo command (with no options) for the changes to be installed. To boot from this new image, either select new from the graphical boot screen or type new and Enter at the LILO boot prompt. If five seconds is too quick, increase the timeout value (such as 100 for 10 seconds). Options that you can use in the /etc/lilo.conf file are divided into global options, per-image options, and kernel options. There is a lot of documentation available for LILO. For more details on any of the options described here or for other options, you can see the lilo.conf manual page (type man lilo.conf) or any of the documents in /usr/share/doc/lilo*/doc. A few examples follow of global options that you can add to /etc/lilo.conf. Global options apply to LILO as a whole, instead of just to a particular boot image. You can use the default=label option, where label is replaced by an image’s label name, to indicate that a particular image be used as the default boot image. If that option is excluded, the first image listed in the /etc/lilo.conf file is used as the default. For example, to start the image labeled new by default, add the following line to lilo.conf: default=new Change the delay from 5 seconds to something greater if you want LILO to wait longer before starting the default image. This gives you more time to boot a different image. To change the value from 5 seconds (50) to 15 seconds (150), add the following line: delay=150 You can change the message that appears before the LILO prompt by adding that message to a file and changing the message line. For example, you could create a /boot/boot.message file and add the following words to that file: Choose linux, new, or dos. To have that message appear before the boot prompt, add the following line to /etc/lilo.conf: message=/boot/boot.message All per-image options begin with either an image= line (indicating a Linux kernel) or other= (indicating some other kind of operating system, such as Windows XP). The per-image options apply to particular boot images rather than to all images (as global options do). Along with the image or other line is a label= line, which gives a name to that image. The name is what you would select at boot time to boot that image. Here are some of the options that you can add to each of those image definitions: lock This enables automatic recording of boot command lines as the defaults for different boot options. alias=name You can replace name with any name. That name becomes an alias for the image name
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Setting up the /etc/lilo.conf file The /etc/lilo.conf file is where LILO gets the information it needs to find and start bootable partitions and images. By adding options to the /etc/lilo.conf file, you can change the behavior of the boot process. The following is an example of some of the contents of the /etc/lilo.conf file: prompt timeout=50 default=linux boot=/dev/hda map=/boot/map install=/boot/boot.b message=/boot/message linear image=/boot/vmlinuz-2.4.7-10 label=linux initrd=/boot/initrd-2.4.7-10.img read-only root=/dev/hda6 append=”hdc=ide-scsi” other=/dev/hda1 label=dos With prompt on, the boot prompt appears when the system is booted without requiring that any keys are pressed. The timeout value, in this case 50 tenths of a second (5 seconds), defines how long to wait for keyboard input before booting the default boot image. The boot line indicates that the bootable partition is on the hard disk represented by /dev/hda (the first IDE hard disk). The map line indicates the location of the map file (/boot/map, by default). The map file contains the name and locations of bootable kernel images. The install line indicates that the /boot/boot.b file is used as the new boot sector. The message line tells LILO to display the contents of the /boot/message file when booting (that contains the graphical Red Hat boot screen that appears). The linear line causes linear sector addresses to be generated (instead of sector/head/cylinder addresses). In the sample file, there are two bootable partitions. The first (image=/boot/vmlinuz-2.4.7-10) shows an image labeled linux. The root file system (/) for that image is on partition /dev/hda6. Read-only indicates that the file system is first mounted read-only, though it is probably mounted as read/write after a file system check. The inidrd line indicates the location of the initial RAM disk image used to start the system. The second bootable partition, which is indicated by the word other in this example, is on the /dev/hda1 partition. Because it is a Windows ME system, it is labeled a DOS file system. The table line indicates the device that contains the partition. Other bootable images are listed in this file, and you can add another boot image yourself (like one you create from reconfiguring your kernel as discussed in the next section) by installing the new image and changing lilo.conf. After you change lilo.conf, you then must run the lilo command for the changes to take effect. You may have different boot images for kernels that include different features. Here is the procedure for modifying the lilo.conf file: 1. Copy the new image from the directory in which it was created (such as /usr/src/linux/arch/i386/boot) to the /boot directory. Name the file something that reflects its contents, such as zImage-2.4.7-10. 2.
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