SCSI is one of the most versatile interfaces, and it pays for that versatility in potential problems. Linux is usually good about reporting problems with SCSI devices, although the error messages may leave you wondering about the real cause of the problem.

The following list explains many of the common SCSI errors and their probable causes. Find the message that closely matches the error message Linux displays to determine your corrective steps.

One of the most commonly encountered problems is hardware that is not recognized properly. This problem can happen to a CD-ROM, a network card, and even a hard disk. Most of the time, a conflict in the IRQ (interrupt), DMA (Direct Memory Address), or I/O address settings causes this problem. When two devices have the same settings on any one of these three characteristics, Linux and the BIOS may not be able to communicate with the device properly.

A symptom of this problem may be Linux hanging when it tries to find a specific device, as explained in the boot messages. When Linux boots up, it generates messages that explain what it is doing. If you see a message that it is trying to connect to the network card, for example, and it never gets past that point, chances are that the network card has a conflict with another device. (Totally failed cards are very rare and don’t usually stop the boot process, as Linux ignores devices it can’t access. The problem with a working card with conflicting settings is that Linux is getting messages from two devices that don’t act the same.)

To check for conflicts, run a diagnostic utility under DOS, such as MSD or Norton Info. These utilities can show you the current IRQ, DMA, and I/O addresses and pinpoint any conflicts. you can also use them to find available settings. Alternatively, you can check the settings of every device in your system for conflicts. Usually, network cards conflict with sound boards, non-SCSI tape driver cards, video cards, and similar add-on cards. Most cards use DIPs or jumpers to set these parameters, so check them against the documentation. To help isolate the problem, remove cards that are not necessary, such as a sound card, and see whether the boot process moves past the device that caused the hangup.

Another problem that can occur is with SCSI devices (and a few others, although much rarer) that must have specific settings in the kernel image. Some kernels, especially special-purpose kernels that have been developed for non-mainstream adapters, were compiled with settings that are default values for adapters or disk drives, and if the settings have been changed, the kernel hangs up. To check for this type of problem, investigate any documentation that came with the kernel image.

The most common devices in a PC (COM ports, parallel ports, and floppy disks) and their IRQ, DMA, and I/O addresses are shown in in the following list. These are the default values for a PC, but they may be changed by users. Because only two COM ports (serial ports) are usually supported by DOS, they share IRQ values. The I/O addresses are different, though. Both floppy disks share the same I/O addresses, IRQ, and DMA.
Device IRQ DMA I/O Address (Hex)
COM 1 (/dev/ttyS0) 4 N/A 3F8
COM 2 (/dev/ttyS1) 3 N/A 2F8
COM 3 (/dev/ttyS2) 4 N/A 3E8
COM 4 (/dev/ttys3) 3 N/A 2E8
LPT 1 (/dev/lp0) 7 N/A 378-37F
LPT 2 (/dev/lp1) 5 N/A 278-27F
Floppy A (/dev/fd0) 6 2 3F0-3F7
Floppy B (/dev/fd1) 6 2 3F0-3F7

You may have noticed that the serial ports are called /dev/ttyS0, /dev/ttyS1, and so on in the list of devices. Yet they were called /dev/cua0, /dev/cua1, and so on when you configured the modem. The ports are the same (/dev/ttyS0 is the same as /dev/cua0); Linux just handles the devices differently. Don’t get too confused about these device driver names yet. Just remember that /dev/cua refers to a modem port.

Network cards, SCSI adapters, sound boards, video cards, and other peripherals all must have unique IRQ, DMA, and I/O addresses, which can be difficult to arrange with a fully loaded system. For more information on available values, check your device or card installation manual for recommended values and potential conflicts.

When Linux boots, it displays a few messages, one of the most important being a partition check. You see messages like the following:

Partition check:

hda: hda1 hda2 hda3

hdb: hdb1 hdb2
In this example, the first non-SCSI disk has three partitions and the second disk has two. Your system’s output is probably different, of course. If you don’t see any partition information, either the hard disk controller is not recognized properly or the disk drives are not accessible. Check the following potential causes for these problems:

Check the cables inside the computer. The hard disk cable should run from the adapter card to each drive’s connector. Make sure the cables are connected in the proper manner (the red strip on the cable is at pin 1 on the connector).

Check that the power connector is attached to each disk drive. Without power, your drive doesn’t spin up and Linux can’t touch it.

Check the partition table to make sure you created a Linux partition properly.

If the drive is still not working properly with Linux but works OK when you boot DOS, a kernel driver for the hard disk is likely at fault. Some IDE drives, for example, are not as well-behaved (not conforming to the IDE standards) as others, and your IDE kernel driver may not be able to talk to your drives. Try using a different kernel image and see if the problem solves itself. If you are using a SCSI kernel and adapter and the drives are not recognized, use the utilities that came with the SCSI adapter card to force a check of the hard drives. They may have a SCSI ID set incorrectly.

You may encounter a few errors when installing Linux. If you get the message device full, you have run out of disk space and need to either break up the installation into several partitions or install fewer components. If you haven’t yet installed the basic system, you need more disk space. You have to delete your partitions and start the installation process again, allocating more space to Linux.

Errors such as read error, file not found and tar: read error are indicative of a problem with either the disk medium you are installing from, or an incomplete disk set. These problems usually occur with floppy disks and may indicate that you have a bad floppy disk. All you can do in most cases is replace the floppy disk with a new one.

Many different problems can occur while setting up and installing a Linux system, although most of them are self-explanatory from error messages. The following sections look at a few of the most commonly encountered problems.

When Linux is up and running, you may want to install or remove disk sets and other software. You can also check that components of a disk set have been properly installed. A few different utilities are available for this task, but the most common is called pkgtool. When you enter the pkgtool command name at the shell prompt, a menu that enables you to install new software, remove existing software, or view installed files in a package appears on-screen. Figure 3.22 shows the pkgtool menu. You can also use the setup utility for these tasks.

Figure 3.22.
The pkgtool utility is one way to install, remove, or examine software on your Linux system.

To view the contents of a package, select View from the main pkgtool menu, and then choose the name of the package from the list presented. Figure 3.23 shows the list of packages. The list should include all the disk set tools you have installed, as well as any additional software installed after the first installation. Selecting a tool name sends pkgtool to check all the files that should be in the software and report its success. Sometimes the list of software in a package can take a while to appear. Be patient! The list pkgtool presents usually has a brief description of the tool and a list of all the files in the installation. Figure 3.24 shows the entry for the base software package.

Figure 3.23
When you select View from the pkgtool utility, you must choose which package to view.

Figure 3.24
The pkgtool utility shows the components installed for each package on your system.

When the list of files is displayed, you can move through them with the space bar. To leave the list of files, select the Exit option at the bottom of the screen.

The last step in the Linux installation process is setting the boot device. A utility called LILO (Linux Loader) usually boots Linux. LILO can boot your system in several different ways, depending on whether you want to use your system with another operating system. Most of the time, you will want LILO to boot your system into Linux with the option to load DOS (if you have it on your system).

The LILO screens explain most of the choices quite well, but LILO has a few quirks to it. Chapter 4 is devoted to explaining what LILO does and how to make it behave properly. For now, if you are impatient, follow the defaults, but don’t let LILO overwrite your hard disk’s Master Boot Record. Doing so can cause a bit of a hassle when you want to boot DOS. You can, though, let LILO write a boot sector to your Linux partition, and then use fdisk to make either DOS or Linux active. If you’re not too sure what to do with LILO, ignore it for now. You have a boot floppy disk that lets you start your machine. When you better understand LILO, you can set it up the way you want.

As a last step in the installation process, reboot your machine and let Linux boot from the boot floppy disk or from LILO, if you installed it. If everything boots properly, you can use Linux as you normally would. If you experienced problems booting, watch error messages and check the installation process to see which part went screwy. As long as you have your boot disk, you should be able to get into Linux without a problem.

After installing disk sets and creating a boot disk, the setup routine may give you a choice to continue with the installation process by configuring your system or to leave the configuration until later. It’s a good idea to continue with the process because back-tracking can be difficult sometimes. Although the order of prompts and the options presented to you are different depending on the version of the Linux system you are installing, usually you are asked to set up your modem first, as shown in Figure 3.17.

Figure 3.17.
The first configuration information you are asked about is your modem.

If you have a modem installed on your system already, choose the Yes option to configure the port and modem speed now. Alternatively, if you are not sure which port you want to use or want to add the modem later, choose No. If you choose Yes to install a modem, you are asked for the device it is attached to, as shown in Figure 3.18. The devices are named in Linux format, with /dev/cua0 equivalent to COM1, /dev/cua1 equivalent to COM2, and so on. Choose the proper device. If your modem is used by DOS’ COM2 port, for example, scroll to /dev/cua1 and choose OK. If you are not sure which port to use, try /dev/cua1, as most mouse ports are COM1 (/dev/cua0). You can always reconfigure the system later.

Figure 3.18.
Choose the device your modem is attached to by using the Linux /dev/cua conventions.

Next you will be asked whether you want to set up your mouse, as shown in Figure 3.19. You can set the mouse up later, but it’s easier to do it when you first load the Linux software. If you choose to configure the mouse at this time, you have to choose the type of mouse you are using. Figure 3.20 shows the list of currently supported mouse types. Most mouse peripherals are serial, so select the serial mouse that matches your unit. If in doubt, choose Microsoft compatible serial mouse.

Figure 3.19.
Linux ask you whether you want to set up your mouse.

Figure 3.20.
Choose the type of mouse your system uses.

After you choose the mouse, you may be asked for more information about it. If the mouse is a serial mouse, you must choose the port it is attached to, as shown in Figure 3.21. The port numbering is similar to the modem port (although the device name is different), with /dev/S0 corresponding to COM1, /dev/S1 to COM2, and so on. Don’t select the same port as the modem! If you are installing a bus mouse, you may be asked for the DMA the mouse uses.

Figure 3.21.
For serial mouse units, you must select the port the mouse is attached to.

Finally, you may be asked whether you want to try out some screen fonts. This step is time-consuming and generally unproductive. It is much better to go with the default fonts for now and modify them later if you really don’t like them. These fonts are used for all character-based messages.

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The setup installation script either asks you or lets you set several pieces of information. First, you need to specify the source of the software. You can usually accomplish this step by by selecting Source from the setup menu when setup starts its automatic installation process. If you have a CD-ROM, it should have been activated during the boot process if the drivers were correct for your hardware. Select the CD-ROM option. You may be asked to further narrow down the type of CD-ROM you have on your system. Choose the exact type(or the one closest to it) and hope for the best. If you are installing from another disk drive partition (such as another Linux partition or a DOS partition), provide the full device and path names. Figure 3.8 shows the Source option choices presented from the setup menu. From here, you can select CD-ROM. If Linux didn’t identify your CD-ROM drive when it booted, you may be presented with another screen and asked to choose the type of CD-ROM drive your system has.

Figure 3.8.
The Source option on the setup menu lets you select where the Linux software will be read from.

The installation program then asks for the target of the installation. The target is where you want the software to be installed. The newly created Linux partition is probably the location you want, so enter the partition’s name. You will probably be asked whether you want to format that partition; answer yes. (Running mkfs or its variants does not format the partition for you.)

Next, Linux displays a list of the disk sets you can install. You may get to this screen through the normal installation process, or you can select Disk Sets from the setup menu. Choose the ones you want. The list of disk sets is usually a scrolling window, as shown in Figure 3.9. Make sure you scroll through the entire list and mark the disk sets you want to install.

Figure 3.9.
The scrolling list holds the names of each major package Linux offers.

Some setup versions let you further refine the list of utilities when the disk set is installed. As a last step, verify the information, and then let Linux install itself. If this process doesn’t start automatically, choose the Install option from the setup menu. Linux may double-check with you that you want to install the disk sets you’ve selected. This screen message looks similar to the one shown in Figure 3.10. This is your last chance to change your mind before Linux starts copying files to your hard drive. After you tell Linux to go ahead and install the software, watch for messages and prompts, and follow any on-screen instructions. If you are installing from a floppy disk, you will be prompted at intervals to change to the next disk in the disk set.

Figure 3.10.
The Linux installation routine usually stops and prompts you before it starts installing software.

As Linux installs software, it displays status screens like the one shown in Figure 3.11 whenever the disk set is changed. As each piece of software in a disk set is installed, its name, size, and a brief description is often displayed, as shown in Figure 3.12. Occasionally, you will be asked to choose whether to install a particular component, as shown in Figure 3.13. Choosing yes installs the package described on the screen; choosing no (use the scroll key to display the no option) skips that package and moves to the next.

Figure 3.11.
As Linux installs each selected disk set, setup displays the letter of the set. The e set being installed here is the GNU Emacs editor.

Figure 3.12.
Each package in a disk set that is installed by default is displayed in a status message, along with the size and brief description of the package.

Figure 3.13.
Some disk sets contain optional components. When one is encountered, you are presented with a screen like this one that describes the package and asks whether you want to install it.

Creating a Boot Disk

At the end of the installation routine, you may be prompted whether you want to create a boot disk. Figure 3.14 shows this screen from the Linux CD-ROM included with this book. The boot disk enables you to access the system at any time, especially if the normal boot process fails. You should always make a boot disk for emergency purposes. This disk is not the same as the boot floppy disk you made to start the installation (which is only useful when you reinstall from scratch).

Figure 3.14.
During the installation process, setup may ask you whether you want to create a boot disk.

When you choose to create a boot disk, Linux prompts you for a floppy disk, as shown in Figure 3.15. Insert a floppy disk in the drive and choose Yes. (Choosing No abandons the creation of the boot disk.) Linux then proceeds to copy the the kernel image and some extra information to the floppy disk. While Linux is creating the boot disk, it shows you a message like the one in Figure 3.16.

Figure 3.15.
When you choose to create a boot disk, Linux prompts you to insert a floppy disk in the drive and choose Yes.

Figure 3.16.
This screen shows the progress of the creation of the boot disk.

After you create and format the partitions and create the filesystems, you can install the Linux software. This step may be automated, depending on the installation procedure included with your Linux distribution. Most versions of Linux include a utility called setup that installs the software for you. From the Linux prompt, type the command

setup
If you are running the color root image, you get graphic, full-screen windows for the installation process. Other root images use character-based installation messages instead. Many users who install Linux frequently avoid the color root image because it can take a little longer to answer all the questions the script poses and some typing errors are difficult to correct. Whichever root image you choose, carefully read each screen.

The setup utility supplied with the Linux system on this book’s CD-ROM is shown in Figure 3.7. Some minor variations in menu choices exist between versions of Linux, but the primary options are much the same.

Figure 3.7.
The most common setup utility menu.

Linux presents you with many choices during the installation. Although the default choices are correct for most people, check that the default is what you want. You have the option of letting Linux install everything without your prompting, except when disk sets change, but you should use this option only if you know exactly what is going on your disk. If you are installing Linux for the first time or want to choose the software to be installed by examining descriptions of each package, use the verbose options to show all messages and let you control the process.