Running Linux, 5th Edition (2009)
Part I. Enjoying and Being Productive on Linux
Chapter 2. Preinstallation and Installation
This chapter represents your first step in installing Linux. We describe how to obtain the Linux software, in the form of one of the various prepackaged distributions , and how to prepare your system. We include ways to partition disks so that Linux can coexist with Windows or another operating system.
As we have mentioned, there is no single "official" distribution of the Linux software; there are, in fact, many distributions, each serving a particular purpose and set of goals. These distributions are available via anonymous FTP from the Internet and via mail on CD-ROM and DVD, as well as in retail stores.
Distributions of Linux
Because Linux is free software, no single organization or entity is responsible for releasing and distributing the software. Therefore, anyone is free to put together and distribute the Linux software, as long as the restrictions in the GPL (and other licenses that may be used) are observed. The upshot of this is that there are many distributions of Linux, available via anonymous FTP or mail order.
You are now faced with the task of deciding on a particular distribution of Linux that suits your needs. Not all distributions are alike. Many of them come with just about all the software you'd need to run a complete system—and then some. Other Linux distributions are "small" distributions intended for users without copious amounts of disk space.
You might also want to consider that distributions have different target groups. Some are meant more for businesses, others more for the home user. Some put more emphasis on server use, others on desktop use.
How can you decide among all these distributions? If you have access to Usenet news, or another computer conferencing system such as web-based discussion boards, you might want to ask there for opinions from people who have installed Linux. Even better, if you know someone who has installed Linux, ask him for help and advice. In actuality, most of the popular Linux distributions contain roughly the same set of software, so the distribution you select is more or less arbitrary.
A particularly interesting type of distribution is the so-called live CD, such as Knoppix (http://www.knoppix.org). These distributions boot from CD and do not require any installation at all; they keep all information in RAM, but can still access your hard drive and other hardware. Besides being a very convenient way of test-driving Linux without having to wipe out anything else, they are also a very good way of rescuing a system that has become unbootable. More about salvaging booting problems will follow later in this book.
Getting Linux via Mail Order or Other Hard Media
If you don't have high-speed Internet access, you can get many Linux distributions via mail order on CD-ROM or DVD. Many distributors accept credit cards as well as international orders, so no matter where you live, you should be able to obtain Linux in this way.
Linux is free software, but distributors are allowed by the GPL to charge a fee for it. Therefore, ordering Linux via mail order might cost you between U.S. $5 and U.S. $150, depending on the distribution. However, if you know people who have already purchased or downloaded a release of Linux, you are free to borrow or copy their software for your own use. Linux distributors are not allowed to restrict the license or redistribution of the software in any way. If you are thinking about installing an entire lab of machines with Linux, for example, you need to purchase only a single copy of one of the distributions, which can be used to install all the machines. There is one exception to this rule, though: in order to add value to their distribution, some vendors include commercial packages that you might not be allowed to install on several machines. If this is the case, it should be explicitly stated on the package.
Another advantage with buying a distribution is that you often get installation support; that is, you can contact the distributor by phone or email and get help if you run into trouble during the installation.
Many Linux user groups offer their own distributions; see if there's a user group near you. For special platforms like Alpha, a user group may be an excellent place to get Linux.
Getting Linux from the Internet
If you have access to the Internet, the easiest way to obtain Linux is via anonymous FTP. One major FTP site is ftp://ftp.ibiblio.org, and the various Linux distributions can be found there in the directory /pub/Linux/distributions. In many countries, there are local mirrors of this server from which you should be able to get the same software faster.
When downloading the Linux software, be sure to use binary mode for all file transfers (with most FTP clients, the command binary enables this mode).
You might run into a minor problem when trying to download files for one system (such as Linux) with another system (such as Windows), because the systems are not always prepared to handle each other's files sensibly. However, with the hints given in this chapter, you should be able to complete the installation process nevertheless.
Some distributions are released via anonymous FTP as a set of disk images. That is, the distribution consists of a set of files, and each file contains the binary image of a floppy. In order to copy the contents of the image file onto the floppy, you can use the RAWRITE.EXE program under Windows. This program copies, block for block, the contents of a file to a floppy, without regard for disk format. RAWRITE.EXE is available on the various Linux FTP sites, including ftp://ftp.ibiblio.org in the directory /pub/Linux/system/Install/rawwrite.
Be forewarned that this is a labor-intensive way of installing Linux: the distribution can easily come to more than 50 floppies. Therefore, only few distributions still provide an installation option that uses floppy disks exclusively. However, combinations of a few floppy disks for the initial booting procedure plus one or more CD-ROMs for the actual software installation are not uncommon.
To proceed, download the set of floppy images and use RAWRITE.EXE with each image in turn to create a set of floppies. Boot from the so-called boot floppy, and you're ready to roll. The software is usually installed directly from the floppies, although some distributions allow you to install from a Windows partition on your hard drive, while others allow you to install over a TCP/IP network. The documentation for each distribution should describe these installation methods if they are available.
If you have access to a Unix workstation with a floppy drive, you can also use the dd command to copy the file image directly to the floppy. A command such as dd of=/dev/rfd0 if=foo bs=18k will "raw write" the contents of the file foo to the floppy device on a Sun workstation. Consult your local Unix gurus for more information on your system's floppy devices and the use of dd.
Each distribution of Linux available via anonymous FTP should include a README file describing how to download and prepare the floppies for installation. Be sure to read all available documentation for the release you are using.
Today, some of the bigger Linux distributions are also distributed as one or a few ISO images that you can burn on a CD-ROM or DVD. Downloading these is feasible only for people with big hard disks and a broadband connection to the Internet, due to the enormous amounts of data involved (but remember that you only need the disk space for one ISO image at a time; you can delete the image after having burnt it, and before downloading the next one).
Preparing to Install Linux
After you have obtained a distribution of Linux, you're ready to prepare your system for installation. This takes a certain degree of planning, especially if you're already running other operating systems. In the following sections, we describe how to plan for the Linux installation.
Installation Overview
Although each release of Linux is different, in general the method used to install the software is as follows:
1. Repartition your hard drive(s). If you have other operating systems already installed, you will need to repartition the drives in order to allocate space for Linux. This is discussed in "Repartitioning Concepts" later in this chapter. In some distributions (such as SUSE), this step is integrated into the installation procedure. Check the documentation of your distribution to see whether this is the case. Still, it won't hurt you to follow the steps given here and repartition your hard drive in advance.
2. Boot the Linux installation medium. Each distribution of Linux has some kind of installation medium—usually a boot floppy or a bootable CD-ROM--that is used to install the software. Booting this medium will either present you with some kind of installation program, which will step you through the Linux installation, or allow you to install the software by hand.
3. Create Linux partitions. After repartitioning to allocate space for Linux, you create Linux partitions on that empty space. This is accomplished with the Linux fdisk program, covered in "Editing /etc/fstab," or with some other distribution-specific program, such as the Disk Druid, which comes with Red Hat Linux.
4. Create filesystems and swap space. At this point, you will create one or more filesystems, used to store files, on the newly created partitions. In addition, if you plan to use swap space (which you should, unless you have really huge amounts of physical memory, or RAM), you will create the swap space on one of your Linux partitions. This is covered in the sections "Creating Swap Space" and "Editing /etc/fstab."
5. Install the software on the new filesystems. Finally, you will install the Linux software on your newly created filesystems. After this, if all goes well, it's smooth sailing. This is covered in "Installing the Software." Later, in "Running into Trouble," we describe what to do if anything goes wrong.
People who want to switch back and forth between different operating systems sometimes wonder which to install first: Linux or the other system? We can testify that some people have had trouble installing Windows 95/98/ME after Linux. Windows 95/98/ME tends to wipe out existing boot information when it's installed, so you're safer installing it first and then installing Linux afterward using the information in this chapter. Windows NT/2000/XP seems to be more tolerant of existing boot information, but installing Windows first and then Linux still seems to be the safer alternative.
Many distributions of Linux provide an installation program that will step you through the installation process and automate one or more of the previous steps for you. Keep in mind throughout this chapter and the next that any number of the previous steps may be automated for you, depending on the distribution.
Tip
While preparing to install Linux, the best advice we can give is to take notes during the entire procedure. Write down everything you do, everything you type, and everything you see that might be out of the ordinary. The idea here is simple: if (or when!) you run into trouble, you want to be able to retrace your steps and find out what went wrong. Installing Linux isn't difficult, but there are many details to remember. You want to have a record of all these details so that you can experiment with other methods if something goes wrong. Also, keeping a notebook of your Linux installation experience is useful when you want to ask other people for help — for example, when posting a message to one of the Linux-related Usenet groups or web discussion forums. Your notebook is also something you'll want to show to your grandchildren someday.[*]
Repartitioning Concepts
In general, hard drives are divided into partitions , with one or more partitions devoted to an operating system. For example, on one hard drive you may have several separate partitions—one devoted to, say, Windows, another to FreeBSD, and another two to Linux.
If you already have other software installed on your system, you may need to resize those partitions in order to free up space for Linux. You will then create one or more Linux partitions on the resulting free space for storing the Linux software and swap space. We call this processrepartitioning .
Many Windows systems utilize a single partition inhabiting the entire drive. To Windows, this partition is known as C:. If you have more than one partition, Windows names them D:, E:, and so on. In a way, each partition acts like a separate hard drive.
On the first sector of the disk is a master boot record along with a partition table. The boot record (as the name implies) is used to boot the system. The partition table contains information about the locations and sizes of your partitions.
There are three kinds of partitions : primary, extended, and logical. Of these, primary partitions are used most often. However, because of a limit on the size of the partition table, you can have only four primary partitions on any given drive. This is due to the poor design of MS-DOS and Windows; even other operating systems that originated in the same era do not have such limits.
The way around this four-partition limit is to use an extended partition. An extended partition doesn't hold any data by itself; instead, it acts as a "container" for logical partitions . Therefore, you could create one extended partition, covering the entire drive, and within it create many logical partitions. However, you are limited to only one extended partition per drive.
Linux Partition Requirements
Before we explain how to repartition your drives, you need an idea of how much space you will be allocating for Linux. We discuss how to create these partitions later in this chapter, in "Editing /etc/fstab."
On Unix systems, files are stored on a filesystem, which is essentially a section of the hard drive (or other medium, such as CD-ROM, DVD, or floppy) formatted to hold files. Each filesystem is associated with a specific part of the directory tree; for example, on many systems, there is a filesystem for all the files in the directory /usr, another for /tmp, and so on. The root filesystem is the primary filesystem, which corresponds to the topmost directory, /.
Under Linux, each filesystem lives on a separate partition on the hard drive. For instance, if you have a filesystem for / and another for /usr, you will need two partitions to hold the two filesystems.[*]
Before you install Linux, you will need to prepare filesystems for storing the Linux software. You must have at least one filesystem (the root filesystem), and therefore one partition, allocated to Linux. Many Linux users opt to store all their files on the root filesystem, which, in most cases, is easier to manage than several filesystems and partitions.
However, you may create multiple filesystems for Linux if you wish—for example, you may want to use separate filesystems for /usr and /home. Those readers with Unix system administration experience will know how to use multiple filesystems creatively. In "Creating Filesystems" inChapter 10 we discuss the use of multiple partitions and filesystems.
Why use more than one filesystem? The most commonly stated reason is safety; if, for some reason, one of your filesystems is damaged, the others will (usually) be unharmed. On the other hand, if you store all your files on the root filesystem, and for some reason the filesystem is damaged, you may lose all your files in one fell swoop. This is, however, rather uncommon; if you back up the system regularly, you should be quite safe.
On the other hand, using several filesystems has the advantage that you can easily upgrade your system without endangering your own precious data. You might have a partition for the users' home directories, and when upgrading the system, you leave this partition alone, wipe out the others, and reinstall Linux from scratch. Of course, nowadays distributions all have quite elaborate update procedures, but from time to time, you might want a fresh start.
Another reason to use multiple filesystems is to divvy up storage among multiple hard drives. If you have, say, 300 MB free on one hard drive, and 2 GB free on another, you might want to create a 300-MB root filesystem on the first drive and a 2-GB /usr filesystem on the other. It is possible to have a single filesystem span multiple drives by using a tool called Logical Volume Manager (LVM), but setting this up requires considerable knowledge, unless your distribution's installation program automates it for you.
In summary, Linux requires at least one partition, for the root filesystem. If you wish to create multiple filesystems, you need a separate partition for each additional filesystem. Some distributions of Linux automatically create partitions and filesystems for you, so you may not need to worry about these issues at all.
Another issue to consider when planning your partitions is swap space. Swap space is a portion of the disk used by an operating system to temporarily store parts of programs that were loaded by the user but aren't currently in use. You are not required to use swap space with Linux, but if you have less than 256 MB of physical RAM, it is strongly suggested that you do.
You have two options. The first is to use a swap file that exists on one of your Linux filesystems. You will create the swap file for use as virtual RAM after you install the software. The second option is to create a swap partition, an individual partition to be used only as swap space. Most people use a swap partition instead of a swap file.
A single swap file or partition may be up to 2 GB.[*] If you wish to use more than 2 GB of swap (hardly ever necessary), you can create multiple swap partitions or files—up to 32 in all.
Setting up a swap partition is covered in "Creating Swap Space," later in this chapter, and setting up a swap file is discussed in "Managing Swap Space" in Chapter 10. For instance, if you want to run fdisk on the first SCSI disk in your system, use the command:
# fdisk /dev/sda
/dev/hda (the first IDE drive) is the default if you don't specify one.
If you are creating Linux partitions on more than one drive, run fdisk once for each drive:
# fdisk /dev/hda
Command (m for help):
Here fdisk is waiting for a command; you can type m to get a list of options :
Command (m for help): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)
Command (m for help):
The n command is used to create a new partition. Most other options you won't need to worry about. To quit fdisk without saving any changes, use the q command. To quit fdisk and write the changes to the partition table to disk, use the w command. This is worth repeating: so long as you quit with q without writing, you can mess around as much as you want with fdisk without risking harm to your data. Only when you type w can you cause potential disaster to your data if you do something wrong.
The first thing you should do is display your current partition table and write the information down for later reference. Use the p command to see the information. It is a good idea to copy the information to your notebook after each change you have made to the partition table. If, for some reason, your partition table is damaged, you will not access any data on your hard disk any longer, even though the data itself is still there. But by using your notes, you might be able to restore the partition table and get your data back in many cases by running fdisk again and deleting and re-creating the partitions with the parameters you previously wrote down. Don't forget to save the restored partition table when you are done.
Here is an example of a printed partition table (of a very small hard disk), where blocks, sectors, and cylinders are units into which a hard disk is organized:
Command (m for help): p
Disk /dev/hda: 16 heads, 38 sectors, 683 cylinders
Units = cylinders of 608 * 512 bytes
Device Boot Begin Start End Blocks Id System
/dev/hda1 * 1 1 203 61693 6 DOS 16-bit >=32M
Command (m for help):
In this example, we have a single Windows partition on /dev/hda1, which is 61693 blocks (about 60 MB).[*] This partition starts at cylinder number 1 and ends on cylinder 203. We have a total of 683 cylinders in this disk; so there are 480 cylinders left on which to create Linux partitions.
To create a new partition, use the n command. In this example, we'll create two primary partitions (/dev/hda2 and /dev/hda3) for Linux:
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Here, fdisk is asking which type of the partition to create: extended or primary. In our example, we're creating only primary partitions, so we choose p:
Partition number (1-4):
fdisk will then ask for the number of the partition to create; because partition 1 is already used, our first Linux partition will be number 2:
Partition number (1-4): 2
First cylinder (204-683):
Now, we'll enter the starting cylinder number of the partition. Because cylinders 204 through 683 are unused, we use the first available one (numbered 204). There's no reason to leave empty space between partitions:
First cylinder (204-683): 204
Last cylinder or +size or +sizeM or +sizeK (204-683):
fdisk is asking for the size of the partition we want to create. We can either specify an ending cylinder number, or a size in bytes, kilobytes, or megabytes. Because we want our partition to be 80 MB in size, we specify +80M. When specifying a partition size in this way, fdisk will round the actual partition size to the nearest number of cylinders:
Last cylinder or +size or +sizeM or +sizeK (204-683): +80M
If you see a warning message such as this, it can be ignored. fdisk prints the warning because it's an older program and dates back before the time that Linux partitions were allowed to be larger than 64 MB.
Now we're ready to create our second Linux partition. For sake of demonstration, we'll create it with a size of 10 MB:
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (474-683): 474
Last cylinder or +size or +sizeM or +sizeK (474-683): +10M
At last, we'll display the partition table. Again, write down all this information-- especially the block sizes of your new partitions. You'll need to know the sizes of the partitions when creating filesystems. Also, verify that none of your partitions overlaps:
Command (m for help): p
Disk /dev/hda: 16 heads, 38 sectors, 683 cylinders
Units = cylinders of 608 * 512 bytes
Device Boot Begin Start End Blocks Id System
/dev/hda1 * 1 1 203 61693 6 DOS 16-bit >=32M
/dev/hda2 204 204 473 82080 83 Linux native
/dev/hda3 474 474 507 10336 83 Linux native
As you can see, /dev/hda2 is now a partition of size 82,080 blocks (which corresponds to about 80 MB), and /dev/hda3 is 10,336 blocks (about 10 MB).
Note that most distributions require you to use the t command in fdisk to change the type of the swap partition to "Linux swap," which is numbered 82. You can use the l command to print a list of known partition type codes, and then use the t command to set the type of the swap partition to that which corresponds to "Linux swap."
This way the installation software will be able to automatically find your swap partitions based on type. If the installation software doesn't seem to recognize your swap partition, you might want to rerun fdisk and use the t command on the partition in question.
In the previous example, the remaining cylinders on the disk (numbered 508 to 683) are unused. You may wish to leave unused space on the disk, in case you want to create additional partitions later.
Finally, we use the w command to write the changes to disk and exit fdisk:
Command (m for help): w
#
Keep in mind that none of the changes you make while running fdisk takes effect until you give the w command, so you can toy with different configurations and save them when you're done. Also, if you want to quit fdisk at any time without saving the changes, use the q command. Remember that you shouldn't modify partitions for operating systems other than Linux with the Linux fdisk program.
You may not be able to boot Linux from a partition using cylinders numbered over 1023. Therefore, you should try to create your Linux root partition within the sub-1024 cylinder range, which is almost always possible (e.g., by creating a small root partition in the sub-1024 cylinder range). If, for some reason, you cannot or do not want to do this, you can simply boot Linux from floppy, use the rescue option of the installation CD or DVD, or boot a Linux live CD like Knoppix.
Some Linux distributions require you to reboot the system after running fdisk to allow the changes to the partition table to take effect before installing the software. Newer versions of fdisk automatically update the partition information in the kernel, so rebooting isn't necessary. To be on the safe side, after running fdisk you should reboot from the installation medium before proceeding.
Creating Swap Space
If you are planning to use a swap partition for virtual RAM, you're ready to prepare it.[*] In "Managing Swap Space" in Chapter 10, we discuss the preparation of a swap file, in case you don't want to use an individual partition.
Many distributions require you to create and activate swap space before installing the software. If you have a small amount of physical RAM, the installation procedure may not be successful unless you have some amount of swap space enabled.
The command used to prepare a swap partition is mkswap , and it takes the following form:
mkswap -c partition
where partition is the name of the swap partition. For example, if your swap partition is /dev/hda3, use the command
# mkswap -c /dev/hda3
With older versions of mkswap, you had to specify the size of the partition, which was dangerous, as one typo could destroy your disk logically.
The -c option tells mkswap to check for bad blocks on the partition when creating the swap space. Bad blocks are spots on the magnetic medium that do not hold the data correctly. This occurs only rarely with today's hard disks, but if it does occur, and you do not know about it, it can cause you endless trouble. Always use the -c option to have mkswap check for bad blocks. It will exclude them from being used automatically.
If you are using multiple swap partitions , you need to execute the appropriate mkswap command for each partition.
After formatting the swap space, you need to enable it for use by the system. Usually, the system automatically enables swap space at boot time. However, because you have not yet installed the Linux software, you need to enable it by hand.
The command to enable swap space is swapon, and it takes the following form:
swapon partition
After the mkswap command shown, we use the following command to enable the swap space on /dev/hda3:
# swapon /dev/hda3
Creating the Filesystems
Before you can use your Linux partitions to store files, you must create filesystems on them. Creating a filesystem is analogous to formatting a partition under Windows or other operating systems. We discussed filesystems briefly in "Linux Partition Requirements," earlier in this chapter.
Several types of filesystems are available for Linux. Each filesystem type has its own format and set of characteristics (such as filename length, maximum file size, and so on). Linux also supports several third-party filesystem types, such as the Windows filesystem.
The most commonly used filesystem types are the Second Extended Filesystem, or ext2fs and the Third Extended Filesystem, or ext3fs. The ext2fs and ext3fs filesystems are two of the most efficient and flexible filesystems; they allows filenames of up to 256 characters and filesystem sizes of up to 32 terabytes. In "Filesystem Types" in Chapter 10, we discuss the various filesystem types available for Linux. Initially, however, we suggest you use the ext3fs filesystem.
To create an ext3fs filesystem, use the command
mke2fs -j -c partition
where partition is the name of the partition. (Notice that the same command, mke2fs is used for creating both ext2 and ext3 filesystems; it's the -j that makes it a journalled, ext3, filesystem.) For example, to create a filesystem on /dev/hda2, use the command
# mke2fs -j -c /dev/hda2
If you're using multiple filesystems for Linux, you need to use the appropriate mke2fs command for each filesystem.
If you have encountered any problems at this point, see "Running into Trouble," later in this chapter.
Installing the Software
Finally, you are ready to install the software on your system. Every distribution has a different mechanism for doing this. Many distributions have a self-contained program that steps you through the installation . On other distributions, you have to mount your filesystems in a certain subdirectory (such as /mnt) and copy the software to them by hand. On CD-ROM distributions, you may be given the option to install a portion of the software on your hard drive and leave most of the software on the CD-ROM. This is often called a "live filesystem." Such a live filesystem is convenient for trying out Linux before you make a commitment to install everything on your disk.
Some distributions offer several different ways to install the software. For example, you may be able to install the software directly from a Windows partition on your hard drive instead of from floppies. Or you may be able to install over a TCP/IP network via FTP or NFS. See your distribution's documentation for details.
For example, the Slackware distribution requires you to do the following:
1. Create partitions with fdisk.
2. Optionally create swap space with mkswap and swapon (if you have 16 MB or less of RAM).
3. Run the setup program to install the software. setup leads you through a self-explanatory menu system.
The exact method used to install the Linux software differs greatly with each distribution.
You might be overwhelmed by the choice of software to install. Modern Linux distributions can easily contain a thousand or more packages spread over several CD-ROMs. There are basically three methods for selecting the software package:
Selection by task
This is the easiest means of selection for beginners. You don't have to think about whether you need a certain package. You just pick whether your Linux computer should act as a workstation, a development machine, or a network router, and the installation program will pick the appropriate packages for you. In all cases, you can then either refine the selection by hand or come back to the installation program later.
Selection of individual packages by series
With this selection mechanism, all the packages are grouped into series such as "Networking," "Development," or "Graphics." You can go through all the series and pick the individual packages there. This requires more decisions than if you choose selection by task, because you have to decide whether you need each package; however, you can skip an entire series when you are sure that you are not interested in the functions it offers.
Selection of individual packages sorted alphabetically
This method is useful only when you already know which packages you want to install; otherwise, you won't see the forest for the trees.
Choosing one selection method does not exclude the use of the others. Most distributions offer two or more of the aforementioned selection mechanisms.
It might still be difficult to decide which package to pick. Good distributions show a short description of each package on screen to make it easier for you to select the correct ones, but if you are still unsure, our advice is this: when in doubt, leave it out! You can always go back and add packages later.
Modern distributions have a very nifty feature, called dependency tracking . Some packages work only when some other packages are installed (e.g., a graphics viewer might need special graphics libraries to import files). With dependency tracking, the installation program can inform you about those dependencies and will let you automatically select the package you want along with all the ones it depends on. Unless you are very sure about what you are doing, you should always accept this offer, or the package might not work afterward.
Installation programs can help you make your selection and avoid mistakes in other ways. For example, the installation program might refuse to start the installation when you deselect a package that is absolutely crucial for even the most minimal system to boot (like the basic directory structure). Or, it might check for mutual exclusions, such as cases in which you can only have one package or the other, but not both.
Some distributions come with a large book that, among other things, lists all the packages together with short descriptions. It might be a good idea to at least skim those descriptions to see what's in store for you, or you might be surprised when you select the packages and are offered the 25th text editor.
Creating the Boot Floppy or Installing GRUB
Every distribution provides some means of booting your new Linux system after you have installed the software. In many cases, the installation procedure suggests you create a boot floppy, which contains a Linux kernel configured to use your newly created root filesystem. In order to boot Linux, you could boot from this floppy; control is transferred to your hard drive after you boot. On other distributions, this boot floppy is the installation floppy itself. If your system does not contain a floppy drive any more (like many newer systems), be assured that there are always other ways of booting Linux, such as booting directly from CD.
Many distributions give you the option of installing GRUB on your hard drive. GRUB is a program that resides on your drive's master boot record. It boots a number of operating systems, including Windows and Linux, and allows you to select which one to boot at startup time.
In order for GRUB to be installed successfully, it needs to know a good deal of information about your drive configuration: for example, which partitions contain which operating systems, how to boot each operating system, and so on. Many distributions, when installing GRUB, attempt to "guess" at the appropriate parameters for your configuration. Occasionally, the automated GRUB installation provided by some distributions can fail and leave your master boot record in shambles (however, it's very doubtful that any damage to the actual data on your hard drive will take place).
In many cases, it is best to use a boot floppy until you have a chance to configure GRUB yourself, by hand. If you're exceptionally trusting, though, you can go ahead with the automated GRUB installation if it is provided with your distribution.
In "Using GRUB" in Chapter 17, we'll cover in detail how to configure and install GRUB for your particular setup.
Tip
There are other boot loaders besides GRUB, including the older Linux Leader (LILO). The general concepts are the same, though; only the installation and configuration differ.
If everything goes well, congratulations! You have just installed Linux on your system. Go have a cup of tea or something; you deserve it.
In case you ran into trouble, "Running into Trouble," later in this chapter, describes the most common sticking points for Linux installations, and how to get around them.
Additional Installation Procedures
Some distributions of Linux provide a number of additional installation procedures, allowing you to configure various software packages, such as TCP/IP networking, the X Window System, and so on. If you are provided with these configuration options during installation, you may wish to read ahead in this book for more information on how to configure this software. Otherwise, you should put off these installation procedures until you have a complete understanding of how to configure the software.
It's up to you; if all else fails, just go with the flow and see what happens. It's doubtful that anything you do incorrectly now cannot be undone in the future (knock on wood).
[*] Matt shamefully admits that he kept a notebook of all his tribulations with Linux for the first few months of working with the system. It is now gathering dust on his bookshelf.
[*] Notice that this applies to filesystems only, not to directories. Of course, you can have any number of directory trees off the root directory in the same filesystem.
[*] This value applies to machines with Intel processors. On other architectures it can be both higher and lower.
[*] A block, under Linux, is 1024 bytes.
[*] Again, some distributions of Linux prepare the swap space for you automatically, or via an installation menu option.
Post-Installation Procedures
After you have completed installing the Linux software, you should be able to reboot the system, log in as root, and begin exploring the system. (Each distribution has a different method for doing this; follow the instructions given by the distribution.)
Before you strike out on your own, however, there are some tasks you should do now that may save you a lot of grief later. Some of these tasks are trivial if you have the right hardware and Linux distribution; others may involve a little research on your part, and you may decide to postpone them.
Creating a User Account
In order to start using your system, you need to create a user account for yourself. Eventually, if you plan to have other users on your system, you'll create user accounts for them as well. But before you begin to explore you need at least one account.
Why is this? Every Linux system has several preinstalled accounts, such as root. The root account, however, is intended exclusively for administrative purposes. As root you have all kinds of privileges and can access all files on your system.
However, using root can be dangerous, especially if you're new to Linux. Because there are no restrictions on what root can do, it's all too easy to mistype a command, inadvertently delete files, damage your filesystem, and so on. You should log in as root only when you need to perform system administration tasks, such as fixing configuration files, installing new software, and so on. See "Maintaining the System" in Chapter 10 for details.[*]
For normal usage, you should create a standard user account. Unix systems have built-in security that prevents users from deleting other users' files and corrupting important resources, such as system configuration files. As a regular user, you'll be protecting yourself from your own mistakes. This is especially true for users who don't have Unix system administration experience.
Many Linux distributions provide tools for creating new accounts. These programs are usually called useradd or adduser. As root, invoking one of these commands should present you with a usage summary for the command, and creating a new account should be fairly self-explanatory.
Most modern distributions provide a generic system administration tool for various tasks, one of which is creating a new user account.
Again, other distributions, such as SUSE Linux, Red Hat Linux, or Mandriva, integrate system installation and system administration in one tool (e.g., yast or yast2 on SUSE Linux).
If all else fails, you can create an account by hand. Usually, all that is required to create an account is the following:
1. Edit the file /etc/passwd to add the new user. (Doing this with vipw--instead of editing the file directly — will protect you against concurrent changes of the password file, but vipw is not available on all distributions.)
2. Optionally edit the file /etc/shadow to specify "shadow password" attributes for the new user.
3. Create the user's home directory.
4. Copy skeleton configuration files (such as .bashrc) to the new user's home directory. These can sometimes be found in the directory /etc/skel.
We don't want to go into great detail here: the particulars of creating a new user account can be found in virtually every book on Unix system administration. We also talk about creating users in "Managing User Accounts" in Chapter 11. You should be able to find a tool that takes care of these details for you.
Keep in mind that to set or change the password on the new account, you use the passwd command. For example, to change the password for the user duck, issue the following command:
# passwd duck
This will prompt you to set or change the password for duck. If you execute the passwd command as root, it will not prompt you for the original password. In this way, if you have forgotten your old password but can still log in as root, you can reset it.
Getting Online Help
Linux provides online help in the form of manual pages. Throughout this book, we'll be directing you to look at the manual pages for particular commands to get more information. Manual pages describe programs and applications on the system in detail, and it's important for you to learn how to access this online documentation in case you get into a bind.
To get online help for a particular command, use the man command. For example, to get information on the passwd command, type the following command:
$ man passwd
This should present you with the manual page for passwd.
Usually, manual pages are provided as an optional package with most distributions, so they won't be available unless you have opted to install them. However, we very strongly advise you to install the manual pages. You will feel lost many times without them.
In addition, certain manual pages may be missing or incomplete on your system. It depends on how complete your distribution is and how up-to-date the manual pages are.
Linux manual pages also document system calls, library functions, configuration file formats, and kernel internals. In "Manual Pages" in Chapter 4, we describe their use in more detail.
Besides traditional manual pages, there are also so-called Info pages. These can be read with the text editor Emacs, the command info, or one of many graphical info readers available.
Many distributions also provide documentation in HTML format that you can read with any web browser, such as Konqueror, as well as with Emacs.
Finally, there are documentation files that are simply plain text. You can read these with any text editor or simply with the command more.
If you cannot find documentation for a certain command, you can also try running it with either the -h or -help option. Most commands then provide a brief summary of their usage.
Editing /etc/fstab
In order to ensure that all your Linux filesystems will be available when you reboot the system, you may need to edit the file /etc/fstab, which describes your filesystems. Many distributions automatically generate the /etc/fstab file for you during installation, so all may be well. However, if you have additional filesystems that were not used during the installation process, you may need to add them to /etc/fstab in order to make them available. Swap partitions should be included in /etc/fstab as well.
In order to access a filesystem, it must be mounted on your system. Mounting a filesystem associates that filesystem with a particular directory. For example, the root filesystem is mounted on /, the /usr filesystem on /usr, and so on. (If you did not create a separate filesystem for /usr, all files under /usr will be stored on the root filesystem.)
We don't want to smother you with technical details here, but it is important to understand how to make your filesystems available before exploring the system. For more details on mounting filesystems, see "Mounting Filesystems" in Chapter 10, or any book on Unix system administration.
The root filesystem is automatically mounted on / when you boot Linux. However, your other filesystems must be mounted individually. Usually, this is accomplished with the command:
# mount -av
in one of the system startup files in /etc/rc.d or wherever your distribution stores its configuration files. This tells the mount command to mount any filesystems listed in the file /etc/fstab. Therefore, in order to have your filesystems mounted automatically at boot time, you need to include them in /etc/fstab. (Of course, you could always mount the filesystems by hand, using the mount command after booting, but this is unnecessary work.)
Here is a sample /etc/fstab file, shortened by omitting the last two parameters in each line, which are optional and not relevant to the discussion here. In this example, the root filesystem is on /dev/hda1, the /home filesystem is on /dev/hdb2, and the swap partition is on /dev/hdb1:
# /etc/fstab
# device directory type options
#
/dev/hda1 / ext3 defaults
/dev/hdb2 /home ext3 defaults
/dev/hdb1 none swap sw
/proc /proc proc defaults
The lines beginning with the "#" character are comments. Also, you'll notice an additional entry for /proc. /proc is a "virtual filesystem" used to gather process information by commands such as ps.
As you can see, /etc/fstab consists of a series of lines. The first field of each line is the device name of the partition, such as /dev/hda1. The second field is the mount point--the directory where the filesystem is mounted. The third field is the type; Linux ext3fs filesystems should use ext3 for this field. swap should be used for swap partitions. The fourth field is for mounting options. You should use defaults in this field for filesystems and sw for swap partitions.
Using this example as a model, you should be able to add entries for any filesystems not already listed in the /etc/fstab file.
How do we add entries to the file? The easiest way is to edit the file, as root, using an editor such as vi or Emacs. We won't get into the use of text editors here. vi and Emacs are both covered in Chapter 19.
After editing the file, you'll need to issue the command:
# /bin/mount -a
or reboot for the changes to take effect.
If you're stuck at this point, don't be alarmed. We suggest that Unix novices do some reading on basic Unix usage and system administration. We offer a lot of introductory material in upcoming chapters, and most of the remainder of this book is going to assume familiarity with these basics, so don't say we didn't warn you.
Shutting Down the System
You should never reboot or shut down your Linux system by pressing the reset switch or simply turning off the power. As with most Unix systems, Linux caches disk writes in memory. Therefore, if you suddenly reboot the system without shutting down cleanly, you can corrupt the data on your drives. Note, however, that the "Vulcan nerve pinch" (pressing Ctrl-Alt-Delete in unison) is generally safe: the kernel traps the key sequence and passes it to the init process, which, in turn, initiates a clean shutdown of the system (or whatever it is configured to do in this case; see "init, inittab, and rc Files" in Chapter 17). Your system configuration might reserve the Ctrl-Alt-Delete for the system administrator so that normal users cannot shut down the network server that the whole department depends upon. To set permissions for this keystroke combination, create a file called /etc/shutdown.allow that lists the names of all the users who are allowed to shut down the machine.
The easiest way to shut down the system is with the shutdown command. As an example, to shut down and reboot the system immediately, use the following command as root:
# shutdown -r now
This will cleanly reboot your system. The manual page for shutdown describes the other available command-line arguments. Instead of now, you can also specify when the system should be shut down. Most distributions also provide halt, which calls shutdown now. Some distributions also provide poweroff, which actually shuts down the computer and turns it off. Whether it works depends on the hardware and the BIOS (which must support APM or ACPI), not on Linux.
[*] A side note: on a Windows 95/98/ME system, the user is always the equivalent of a root user, whether that power is needed or not.
Running into Trouble
Almost everyone runs into some kind of snag or hang-up when attempting to install Linux the first time. Most of the time, the problem is caused by a simple misunderstanding. Sometimes, however, it can be something more serious, such as an oversight by one of the developers or a bug.
This section describes some of the most common installation problems and how to solve them. It also describes unexpected error messages that can pop up during installations that appear to be successful.
In general, the proper boot sequence is as follows:
1. After booting from the LILO prompt, the system must load the kernel image from floppy. This may take several seconds; you know things are going well if the floppy drive light is still on.
2. While the kernel boots, SCSI devices must be probed for. If you have no SCSI devices installed, the system will hang for up to 15 seconds while the SCSI probe continues; this usually occurs after the line:
lp_init: lp1 exists (0), using polling driver
appears on your screen.
3. After the kernel is finished booting, control is transferred to the system bootup files on the floppy. Finally, you will be presented with a login prompt (either a graphical or a textual one) or be dropped into an installation program. If you are presented with a login prompt such as:
Linux login:
you should then log in (usually as root or install--this varies with each distribution). After you enter the username, the system may pause for 20 seconds or more while the installation program or shell is being loaded from floppy. Again, the floppy drive light should be on. Don't assume the system is hung.
Problems with Booting the Installation Medium
When attempting to boot the installation medium for the first time, you may encounter a number of problems. Note that the following problems are not related to booting your newly installed Linux system. See "Problems After Installing Linux," later in this chapter, for information on these kinds of pitfalls.
A floppy or medium error occurs when attempting to boot
The most popular cause for this kind of problem is a corrupt boot floppy. Either the floppy is physically damaged, in which case you should re-create the disk with a brand-new floppy, or the data on the floppy is bad, in which case you should verify that you downloaded and transferred the data to the floppy correctly. In many cases, simply re-creating the boot floppy will solve your problems. Retrace your steps and try again.
If you received your boot floppy from a mail-order vendor or some other distributor, instead of downloading and creating it yourself, contact the distributor and ask for a new boot floppy — but only after verifying that this is indeed the problem. This can, of course, be difficult, but if you get funny noises from your floppy drive or messages like cannot read sector , chances are that your medium is damaged.
The system hangs during boot or after booting
After the installation medium boots, you see a number of messages from the kernel itself, indicating which devices were detected and configured. After this, you are usually presented with a login prompt, allowing you to proceed with installation (some distributions instead drop you right into an installation program of some kind). The system may appear to hang during several of these steps. Be patient; loading software from floppy is very slow. In many cases, the system has not hung at all, but is merely taking a long time. Verify that there is no drive or system activity for at least several minutes before assuming that the system is hung.
Each activity listed at the beginning of this section may cause a delay that makes you think the system has stopped. However, it is possible that the system actually may hang while booting, which can be due to several causes. First of all, you may not have enough available RAM to boot the installation medium. (See the following item for information on disabling the ramdisk to free up memory.)
Hardware incompatibility causes many system hangs. Even if your hardware is supported, you may run into problems with incompatible hardware configurations that are causing the system to hang. See "Hardware Problems," later in this chapter, for a discussion of hardware incompatibilities. "Hardware Requirements" in Chapter 16 lists the currently supported video chipsets, which are a major issue in running graphics on Linux.
The system reports out-of-memory errors while attempting to boot or install the software
This problem relates to the amount of RAM you have available. Keep in mind that Linux itself requires at least 8 MB of RAM to run at all; almost all current distributions of Linux require 32 MB or more. On systems with 16 MB of RAM or less, you may run into trouble booting the installation medium or installing the software itself. This is because many distributions use a ramdisk, which is a filesystem loaded directly into RAM, for operations while using the installation medium. The entire image of the installation boot floppy, for example, may be loaded into a ramdisk, which may require more than 1 MB of RAM.
The solution to this problem is to disable the ramdisk option when booting the install medium. Each distribution has a different procedure for doing this. Please see your distribution documentation for more information.
You may not see an out-of-memory error when attempting to boot or install the software; instead, the system may unexpectedly hang or fail to boot. If your system hangs, and none of the explanations in the previous section seems to be the cause, try disabling the ramdisk.
The system reports an error, such as "Permission denied" or "File not found," while booting
This is an indication that your installation boot medium is corrupt. If you attempt to boot from the installation medium (and you're sure you're doing everything correctly), you should not see any such errors. Contact the distributor of your Linux software and find out about the problem, and perhaps obtain another copy of the boot medium if necessary. If you downloaded the boot disk yourself, try re-creating the boot disk, and see if this solves your problem.
The system reports the error "VFS: Unable to mount root" when booting
This error message means that the root filesystem (found on the boot medium itself) could not be found. This means that either your boot medium is corrupt or you are not booting the system correctly.
For example, many CD-ROM/DVD distributions require you to have the CD-ROM/DVD in the drive when booting. Also be sure that the CD-ROM/DVD drive is on, and check for any activity. It's also possible the system is not locating your CD-ROM/DVD drive at boot time; see "Hardware Problems" for more information.
If you're sure you are booting the system correctly, your boot medium may indeed be corrupt. This is an uncommon problem, so try other solutions before attempting to use another boot floppy or tape. One handy feature here is Red Hat's new mediacheck option on the CD-ROM/DVD. This will check if the CD is OK.
Hardware Problems
The most common problem encountered when attempting to install or use Linux is an incompatibility with hardware . Even if all your hardware is supported by Linux, a misconfiguration or hardware conflict can sometimes cause strange results: your devices may not be detected at boot time, or the system may hang.
It is important to isolate these hardware problems if you suspect they may be the source of your trouble. In the following sections, we describe some common hardware problems and how to resolve them.
Isolating hardware problems
If you experience a problem you believe is hardware related, the first thing to do is attempt to isolate the problem. This means eliminating all possible variables and (usually) taking the system apart, piece by piece, until the offending piece of hardware is isolated.
This is not as frightening as it may sound. Basically, you should remove all nonessential hardware from your system (after turning the power off), and then determine which device is actually causing the trouble — possibly by reinserting each device, one at a time. This means you should remove all hardware other than the floppy and video controllers, and, of course, the keyboard. Even innocent-looking devices, such as mouse controllers, can wreak unknown havoc on your peace of mind unless you consider them nonessential. So, to be sure, really remove everything that you don't absolutely need for booting when experimenting, and add the devices one by one later when reassembling the system.
For example, let's say the system hangs during the Ethernet board detection sequence at boot time. You might hypothesize that there is a conflict or problem with the Ethernet board in your machine. The quick and easy way to find out is to pull the Ethernet board and try booting again. If everything goes well when you reboot, you know that either the Ethernet board is not supported by Linux, or there is an address or IRQ conflict with the board. In addition, some badly designed network boards (mostly ISA-based NE2000 clones, which are luckily dying out by now) can hang the entire system when they are auto-probed. If this appears to be the case for you, your best bet is to remove the network board from the system during the installation and put it back in later, or pass the appropriate kernel parameters during boot-up so that auto-probing of the network board can be avoided. The most permanent fix is to dump that card and get a new one from another vendor that designs its hardware more carefully.
What does "address or IRQ conflict" mean, you may ask? All devices in your machine use an interrupt request line, or IRQ, to tell the system they need something done on their behalf. You can think of the IRQ as a cord the device tugs when it needs the system to take care of some pending request. If more than one device is tugging on the same cord, the kernel won't be able to determine which device it needs to service. Instant mayhem.
Therefore, be sure all your installed non-PCI/AGP devices are using unique IRQ lines. In general, the IRQ for a device can be set by jumpers on the card; see the documentation for the particular device for details. Some devices do not require an IRQ at all, but it is suggested you configure them to use one if possible (the Seagate ST01 and ST02 SCSI controllers are good examples). The PCI bus is more cleverly designed, and PCI devices can and do quite happily share interrupt lines.
In some cases, the kernel provided on your installation medium is configured to use a certain IRQ for certain devices. For example, on some distributions of Linux, the kernel is preconfigured to use IRQ 5 for the TMC-950 SCSI controller, the Mitsumi CD-ROM controller, and the bus mouse driver. If you want to use two or more of these devices, you'll need first to install Linux with only one of these devices enabled, then recompile the kernel in order to change the default IRQ for one of them. (See "Building a New Kernel" in Chapter 18 for information on recompiling the kernel.)
Another area where hardware conflicts can arise is with DMA channels, I/O addresses , and shared memory addresses . All these terms describe mechanisms through which the system interfaces with hardware devices. Some Ethernet boards, for example, use a shared memory address as well as an IRQ to interface with the system. If any of these are in conflict with other devices, the system may behave unexpectedly. You should be able to change the DMA channel, I/O, or shared memory addresses for your various devices with jumper settings. (Unfortunately, some devices don't allow you to change these settings.)
The documentation for your various hardware devices should specify the IRQ, DMA channel, I/O address, or shared memory address the devices use, and how to configure them. Of course, a problem here is that some of these settings are not known before the system is assembled and may thus be undocumented. Again, the simple way to get around these problems is to temporarily disable the conflicting devices until you have time to determine the cause of the problem.
Table 2-1 lists IRQ and DMA channels used by various "standard" devices found on most systems. Almost all systems have some of these devices, so you should avoid setting the IRQ or DMA of other devices to these values.
Table 2-1. Common device settings
|
Device |
I/O address |
IRQ |
DMA |
|
ttyS0 (COM1) |
3f8 |
4 |
n/a |
|
ttyS1 (COM2) |
2f8 |
3 |
n/a |
|
ttyS2 (COM3) |
3e8 |
4 |
n/a |
|
ttyS3 (COM4) |
2e8 |
3 |
n/a |
|
lp0 (LPT1) |
378 - 37f |
7 |
n/a |
|
lp1 (LPT2) |
278 - 27f |
5 |
n/a |
|
fd0, fd1 (floppies 1 and 2) |
3f0 - 3f7 |
6 |
2 |
|
fd2, fd3 (floppies 3 and 4) |
370 - 377 |
10 |
3 |
Problems recognizing hard drive or controller
When Linux boots, you see a series of messages on your screen, such as the following:
Console: switching to colour frame buffer device 147x55
Real Time Clock Driver v1.12
Serial: 8250/16550 driver $Revision: 1.1 $ 48 ports, IRQ sharing enabled
ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
Using anticipatory io scheduler
Floppy drive(s): fd0 is 1.44M
FDC 0 is a post-1991 82077
...
Here, the kernel is detecting the various hardware devices present on your system. At some point, you should see a line like the following:
hda: hda1 hda2 hda3 hda4 < hda5 hda6 hda7 >
If, for some reason, your drives or partitions are not recognized, you will not be able to access them in any way.
Several conditions can cause this to happen:
Hard drive or controller not supported
If you are using a hard drive or controller (IDE, SCSI, or otherwise) not supported by Linux, the kernel will not recognize your partitions at boot time.
Drive or controller improperly configured
Even if your controller is supported by Linux, it may not be configured correctly. (This is a problem particularly for SCSI controllers ; most non-SCSI controllers should work fine without additional configuration.)
Refer to the documentation for your hard drive and controller for information on solving these kinds of problems. In particular, many hard drives will need to have a jumper set if they are to be used as a slave drive (e.g., as the second hard drive). The acid test for this kind of condition is to boot up Windows or some other operating system known to work with your drive and controller. If you can access the drive and controller from another operating system, the problem is not with your hardware configuration.
See the previous section, "Isolating hardware problems," for information on resolving possible device conflicts and the following section, "Problems with SCSI controllers and devices," for information on configuring SCSI devices.
Controller properly configured, but not detected
Some BIOS-less SCSI controllers require the user to specify information about the controller at boot time. The following section, "Problems with SCSI controllers and devices," describes how to force hardware detection for these controllers.
Hard drive geometry not recognized
Some older systems, such as the IBM PS/ValuePoint, do not store hard drive geometry information in the CMOS memory where Linux expects to find it. Also, certain SCSI controllers need to be told where to find drive geometry in order for Linux to recognize the layout of your drive.
Most distributions provide a boot option to specify the drive geometry. In general, when booting the installation medium, you can specify the drive geometry at the LILO boot prompt with a command such as:
boot: linux hd=cylinders
,heads
,sectors
where cylinders, heads, and sectors correspond to the number of cylinders, heads, and sectors per track for your hard drive.
After installing the Linux software, you can install LILO, allowing you to boot from the hard drive. At that time, you can specify the drive geometry to the LILO installation procedure, making it unnecessary to enter the drive geometry each time you boot. See "Using GRUB" in Chapter 17 for more about LILO.
Problems with SCSI controllers and devices
Presented here are some of the most common problems with SCSI controllers and devices, such as CD-ROMs, hard drives, and tape drives. If you are having problems getting Linux to recognize your drive or controller, read on. Let us again emphasize that most distributions use a modularized kernel and that you might have to load a module supporting your hardware during an early phase of the installation process. This might also be done automatically for you.
The Linux SCSI HOWTO contains much useful information on SCSI devices in addition to that listed here. SCSIs can be particularly tricky to configure at times.
It might be a false economy, for example, to use cheap cables, especially if you use wide SCSI. Cheap cables are a major source of problems and can cause all kinds of failures, as well as major headaches. If you use SCSI, use proper cabling.
Here are common problems and possible solutions:
A SCSI device is detected at all possible IDs
This problem occurs when the system straps the device to the same address as the controller. You need to change the jumper settings so that the drive uses a different address from the controller itself.
Linux reports sense errors, even if the devices are known to be error-free
This can be caused by bad cables or by bad termination. If your SCSI bus is not terminated at both ends, you may have errors accessing SCSI devices. When in doubt, always check your cables. In addition to disconnected cables, bad-quality cables are a common source of troubles.
SCSI devices report timeout errors
This is usually caused by a conflict with IRQ, DMA, or device addresses. Also, check that interrupts are enabled correctly on your controller.
SCSI controllers using BIOS are not detected
Detection of controllers using BIOS will fail if the BIOS is disabled, or if your controller's "signature" is not recognized by the kernel. See the Linux SCSI HOWTO for more information about this.
Controllers using memory-mapped I/O do not work
This happens when the memory-mapped I/O ports are incorrectly cached. Either mark the board's address space as uncacheable in the XCMOS settings, or disable the cache altogether.
When partitioning, you get a warning "cylinders > 1024," or you are unable to boot from a partition using cylinders numbered above 1023
BIOS limits the number of cylinders to 1024, and any partition using cylinders numbered above this won't be accessible from the BIOS. As far as Linux is concerned, this affects only booting; once the system has booted, you should be able to access the partition. Your options are to either boot Linux from a boot floppy or to boot from a partition using cylinders numbered below 1024. See "Creating the Boot Floppy or Installing GRUB," earlier in this chapter.
CD-ROM drive or other removable media devices are not recognized at boot time
Try booting with a CD-ROM (or disk) in the drive. This is necessary for some devices.
If your SCSI controller is not recognized, you may need to force hardware detection at boot time. This is particularly important for SCSI controllers without BIOS. Most distributions allow you to specify the controller IRQ and shared memory address when booting the installation medium. For example, if you are using a TMC-8xx controller, you may be able to enter:
boot: linux tmx8xx=interrupt,memory-address
at the LILO boot prompt, where interrupt is the controller IRQ, and memory-address is the shared memory address. Whether you can do this depends on the distribution of Linux you are using; consult your documentation for details.
Problems Installing the Software
Installing the Linux software should be trouble-free if you're lucky. The only problems you might experience would be related to corrupt installation media or lack of space on your Linux filesystems. Here is a list of common problems:
System reports "Read error, file not found" or other errors while attempting to install the software
This is indicative of a problem with your installation medium. If you are installing from floppy, keep in mind that floppies are quite susceptible to media errors of this type. Be sure to use brand-new, newly formatted floppies. If you have a Windows partition on your drive, many Linux distributions allow you to install the software from the hard drive. This may be faster and more reliable than using floppies.
If you are using a CD-ROM, be sure to check the disk for scratches, dust, or other problems that might cause media errors.
The cause of the problem may also be that the medium is in the incorrect format. For example, many Linux distributions require floppies to be formatted in high-density Windows format. (The boot floppy is the exception; it is not in Windows format in most cases.) If all else fails, either obtain a new set of floppies, or re-create the floppies (using new ones) if you downloaded the software yourself.
System reports errors such as "tar: read error" or "gzip: not in gzip format"
This problem is usually caused by corrupt files on the installation medium itself. In other words, your floppy may be error-free, but the data on the floppy is in some way corrupted. For example, if you downloaded the Linux software using text mode, rather than binary mode, your files will be corrupt and unreadable by the installation software. When using FTP, just issue the binary command to set that mode before you request a file transfer.
System reports errors such as "device full" while installing
This is a clear-cut sign that you have run out of space when installing the software. If the disk fills up, not all distributions can clearly recover, so aborting the installation won't give you a working system.
The solution is usually to re-create your filesystems with the mke2fs command, which will delete the partially installed software. You can then attempt to reinstall the software, this time selecting a smaller amount of software to install. If you can't do without that software, you may need to start completely from scratch and rethink your partition and filesystem sizes.
System reports errors such as "read_intr: 0x10" while accessing the hard drive
This is usually an indication of bad blocks on your drive. However, if you receive these errors while using mkswap or mke2fs, the system may be having trouble accessing your drive. This can either be a hardware problem (see "Hardware Problems" earlier in this chapter), or it might be a case of poorly specified geometry. If you used the option:
hd=cylinders,heads,sectors
at boot time to force detection of your drive geometry and incorrectly specified the geometry, you could receive this error. This can also happen if your drive geometry is incorrectly specified in the system CMOS.
System reports errors such as "file not found " or "permission denied "
This problem can occur if the necessary files are not present on the installation medium or if there is a permissions problem with the installation software. For example, some distributions of Linux have been known to have bugs in the installation software itself; these are usually fixed rapidly and are quite infrequent. If you suspect that the distribution software contains bugs, and you're sure that you have done nothing wrong, contact the maintainer of the distribution to report the bug.
If you have other strange errors when installing Linux (especially if you downloaded the software yourself), be sure you actually obtained all the necessary files when downloading.
For example, some people use the FTP command:
mget *.*
when downloading the Linux software via FTP. This will download only those files that contain a "." in their filenames; files without the "." will not be downloaded. The correct command to use in this case is:
mget *
The best advice is to retrace your steps when something goes wrong. You may think that you have done everything correctly, when in fact you forgot a small but important step somewhere along the way. In many cases, just attempting to redownload or reinstall the Linux software can solve the problem. Don't beat your head against the wall any longer than you have to!
Also, if Linux unexpectedly hangs during installation, there may be a hardware problem of some kind. See "Hardware Problems" for hints.
Problems After Installing Linux
You've spent an entire afternoon installing Linux. In order to make space for it, you wiped your Windows and OS/2 partitions and tearfully deleted your copies of SimCity 2000 and Railroad Tycoon 2. You reboot the system and nothing happens. Or, even worse, something happens, but it's not what should happen. What do you do?
In "Problems with Booting the Installation Medium," earlier in this chapter, we covered the most common problems that can occur when booting the Linux installation medium; many of those problems may apply here. In addition, you may be a victim of one of the following maladies.
Problems booting Linux from floppy
If you are using a floppy to boot Linux, you may need to specify the location of your Linux root partition at boot time. This is especially true if you are using the original installation floppy itself and not a custom boot floppy created during installation.
While booting the floppy, hold down the Shift or Ctrl key. This should present you with a boot menu; press Tab to see a list of available options. For example, many distributions allow you to boot from a floppy by entering:
boot: linux root=partition
at the boot menu, where partition is the name of the Linux root partition, such as /dev/hda2. SUSE Linux offers a menu entry early in the installation program that boots your newly created Linux system from the installation boot floppy. Consult the documentation for your distribution for details.
Problems booting Linux from the hard drive
If you opted to install LILO instead of creating a boot floppy, you should be able to boot Linux from the hard drive. However, the automated LILO installation procedure used by many distributions is not always perfect. It may make incorrect assumptions about your partition layout, in which case you need to reinstall LILO to get everything right. Installing LILO is covered in "Using GRUB" in Chapter 17.
Here are some common problems:
System reports "Drive not bootable — Please insert system disk"
You will get this error message if the hard drive's master boot record is corrupt in some way. In most cases, it's harmless, and everything else on your drive is still intact. There are several ways around this:
§ While partitioning your drive using fdisk , you may have deleted the partition that was marked as "active." Windows and other operating systems attempt to boot the "active" partition at boot time (Linux, in general, pays no attention to whether the partition is "active," but the Master Boot Records installed by some distributions like Debian do). You may be able to boot MS-DOS from floppy and run fdisk to set the active flag on your MS-DOS partition, and all will be well.
Another command to try (with MS-DOS 5.0 and higher, including Windows 95/98/ME) is:
FDISK /MBR
This command will attempt to rebuild the hard drive master boot record for booting Windows, overwriting LILO . If you no longer have Windows on your hard drive, you'll need to boot Linux from floppy and attempt to install LILO later. This command does not exist on Windows NT/2000/XP; here the procedure is more involved.
§ If you created a Windows partition using Linux's version of fdisk, or vice versa, you may get this error. You should create Windows partitions only by using Windows' version of fdisk. (The same applies to operating systems other than Windows.) The best solution here is either to start from scratch and repartition the drive correctly, or to merely delete and re-create the offending partitions using the correct version of fdisk.
§ The LILO installation procedure may have failed. In this case, you should boot either from your Linux boot floppy (if you have one) or from the original installation medium. Either of these should provide options for specifying the Linux root partition to use when booting. At boot time, hold down the Shift or Ctrl key and press Tab from the boot menu for a list of options.
When you boot the system from the hard drive, Windows (or another operating system) starts instead of Linux
First of all, be sure you actually installed LILO or GRUB when installing the Linux software. If not, the system will still boot Windows (or whatever other operating system you may have) when you attempt to boot from the hard drive. In order to boot Linux from the hard drive, you need to install LILO or GRUB (see the section "Using GRUB" in Chapter 17).
On the other hand, if you did install LILO, and another operating system boots instead of Linux, you have LILO configured to boot that other operating system by default. While the system is booting, hold down the Shift or Ctrl key and press Tab at the boot prompt. This should present you with a list of possible operating systems to boot; select the appropriate option (usually just linux) to boot Linux.
If you wish to select Linux as the default operating system to boot, you will need to reinstall LILO.
It also may be possible that you attempted to install LILO, but the installation procedure failed in some way. See the previous item on installation.
Problems logging in
After booting Linux, you should be presented with a login prompt:
Linux login:
At this point, either the distribution's documentation or the system itself will tell you what to do. For many distributions, you simply log in as root, with no password. Other possible usernames to try are guest or test.
Most Linux distributions ask you for an initial root password. Hopefully, you have remembered what you typed in during installation; you will need it again now. If your distribution does not ask you for a root password during installation, you can try using an empty password.
If you simply can't log in, consult your distribution's documentation; the username and password to use may be buried in there somewhere. The username and password may have been given to you during the installation procedure, or they may be printed on the login banner. Another option is to log into Linux in single-user mode by typing linux simple at the boot prompt.
One possible cause of this password impasse may be a problem with installing the Linux login and initialization files. If this is the case, you may need to reinstall (at least parts of) the Linux software, or boot your installation medium and attempt to fix the problem by hand.
Problems using the system
If login is successful, you should either be presented with a shell prompt (such as # or $) or be directly taken to a graphical desktop environment such as KDE or Gnome, and can happily roam around your system. The next step in this case is to try the procedures in Chapter 4. However, some initial problems with using the system sometimes creep up.
The most common initial configuration problem is incorrect file or directory permissions. This can cause the error message:
Shell-init: permission denied
to be printed after logging in. (In fact, anytime you see the message permission denied, you can be fairly certain it is a problem with file permissions.)
In many cases, it's a simple matter of using the chmod command to fix the permissions of the appropriate files or directories. For example, some distributions of Linux once used the incorrect file mode 0644 for the root directory (/). The fix was to issue the command:
# chmod 755 /
as root. (File permissions are covered in the section "File Ownership and Permissions" in Chapter 11.) However, in order to issue this command, you need to have booted from the installation medium and mounted your Linux root filesystem by hand—a hairy task for most newcomers.
As you use the system, you may run into places where file and directory permissions are incorrect or software does not work as configured. Welcome to the world of Linux! Although most distributions are quite trouble-free, you can't expect them to be perfect. We don't want to cover all those problems here. Instead, throughout the book we help you to solve many of these configuration problems by teaching you how to find them and fix them yourself. In Chapter 1, we discussed this philosophy in some detail. In Part II, we give hints for fixing many of these common configuration problems.