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发信人: netiscpu (说不如做), 信区: Linux
标 题: [B] Red Hat Linux Unleashed (3)
发信站: 紫 丁 香 (Sat Jul 25 03:08:15 1998), 转信
Installing and Updating Linux
_________________________________________________________________
o Installing Red Hat Linux
# Floppyless Installation
# Floppy-Based Installation
o The Red Hat Installation Routine A Quick Guide
# Choosing Text or Graphics Installation
# Setting Up Your Hard Drive
# Formatting the Partitions
# Setting Up Ethernet
# Setting Up the Mouse
# Configuring X
# Selecting Packages to Install
# Using LILO
o Boot and Root Disks
# Selecting a Boot Kernel and Root Image
# Creating the Boot and Root Floppies
o Partitioning the Hard Disk
# Linux Swap-Space Partition
# Setting Up Partitions
o Install the Linux Partitions
# Linux's fdisk
# Setting Up Linux Partitions
# Enabling the Swap Space For Installation
# Creating the Linux File-System Partition
o Troubleshooting
# Software Installation
# Hard Disk and Disk Controller
# Device Conflicts
o SCSI Problems
# Booting Linux
o Summary
_________________________________________________________________
3
Installing and Updating Linux
The process of installing Red Hat Linux is straightforward, although
there are lots of little problems scattered throughout the process
that can cause hassles. Red Hat Linux is much easier to install than
many other versions of Linux, so you will find the installation goes
quite easily. Common errors that you might make are handled nicely by
the Red Hat installation program, and the system is versatile enough
to handle most configuration requirements.
The essential steps for installing Red Hat Linux are as follows:
1. Create boot and root disks.
2. Boot Linux from floppies.
3. Partition the hard disk.
4. Create a swap file.
5. Create a Linux file system.
6. Install the Linux software.
7. Configure the kernel.
8. Set the boot process.
9. Reboot into Linux from your hard disk.
The process is similar whether you are installing from a CD-ROM or
from a diskette (which may have come from an FTP site, for example).
Because the CD-ROM is the most common form of installation (and the
one included with this book), it is used as the example in this
chapter.
If you are installing from a floppy and have downloaded the
distribution files from an FTP site or copied them from a CD-ROM, you
will need a DOS-formatted floppy for each disk in the distribution
disk set. You can use standard DOS copy commands to copy the disk set
files to the floppy, one floppy for each file in the distribution set.
The files are all numbered so you know which floppy is in which set,
and what their order should be.
Installing Red Hat Linux
Unlike some versions of Linux, Red Hat gives you a number of methods
of installing its operating system that offer versatility and ease of
use. For most people, installation will be a very simple task with
most of the process automated by the Red Hat installation routines.
Users with some special hardware or disk-layout problems will have to
perform a more typical manual installation of Linux. This chapter
covers all the steps you need to install Linux manually, as well as
the brief instructions you need to allow an automated installation.
If you want to try an automated installation of Red Hat Linux, there
are two ways to go. One is called floppyless, as it uses a routine on
the CD-ROM to install itself. This step simply saves you the trouble
of making floppy diskettes; the rest of the installation process is
exactly the same.
The alternative to floppyless installation is to create boot and root
floppies and use those to start up the system and access the CD-ROM.
The following sections discuss both floppyless and floppy-based
methods in more detail.
Floppyless Installation
If your hard disk already has an operating system like DOS, or one
that produces a DOS window, you can try installing directly from the
CD-ROM. Boot into your existing operating system, change to the CD-ROM
drive, and issue the command
REDHAT
at the DOS prompt. You will be asked a series of questions by the
program that help it determine the best images for the boot kernel.
You can also provide any special startup installation commands during
this stage.
______________________________________________________________
NOTE: Do not run the floppyless installation process from inside a
Windows or OS/2 session. Boot your system into DOS or DOS emulation
and run it from there.
______________________________________________________________
The floppyless installation routine guides you through the kernel
determination process by displaying all possible choices on menus and
prompting you for your answers. The process is intuitive and can be
used by anyone who knows the type of hardware installed on their
system. If you are not exactly sure of hardware, you can still try the
floppyless installation; the worst that can happen is you must try
again with different settings.
If the installation process detects some hardware-configuration
issues, it may offer you advice on setting parameters or making
changes. These bits of advice are, for the most part, just that:
advice. You don't have to heed the advice if you don't want. In some
cases, the advice makes a lot of sense (such as resolving IRQ
conflicts), in which case you should take care of the issue.
Floppy-Based Installation
A floppy-based installation requires you to produce three floppies:
one for the boot (kernel) image, and two for the root or swap images.
The following section, entitled "Boot and Root Floppies," looks at the
production of these floppies in detail. After these disks have been
produced, your system is booted with the boot floppy in drive A:.
After the kernel has been read and some diagnostics have been
performed, you are prompted for the first of the root or swap
floppies, then the second floppy, and then the installation procedure
is started.
______________________________________________________________
NOTE: A quick word of advice when using floppies: Red Hat Linux is
particularly sensitive to fast floppy changes. If you hit the
Return key too quickly and the floppy is not in the drive, you will
probably get errors and have to start the boot process all over
again. This occurs when booting and Red Hat asks for the first and
second swap or root floppies. Make sure the diskette is in the
drive, wait a few seconds, then hit Return to prevent any problems.
The disk-change process is not as forgiving as DOS or Windows!
______________________________________________________________
After the boot and root floppies have been loaded, the normal Red Hat
Linux installation routine is started.
The Red Hat Installation Routine A Quick Guide
______________________________________________________________
NOTE: This section gives you a quick overview of the installation
routine and can be used by those experienced with Linux or very
simple hardware setups. If you run into any problems at all during
the installation process, check the more detailed sections later in
this chapter.
______________________________________________________________
After you have successfully loaded your boot and root images either
from disk or CD-ROM, you are launched into the installation routine.
The Red Hat Linux distribution has a very useful menu-driven
installation routine that is much more forgiving of errors than many
other Linux versions. For the most part, you need only read the
screens and make logical choices to have the installation process
continue properly. Many of the steps are automated and occur without
your intervention.
If something happens with the automated installation routine that
causes an error, a warning on the screen is displayed and you will be
dropped into a manual installation routine. This can be used just as
easily as the automated routine; it just takes a little longer. Again,
menu-driven options make the process painless.
You can probably install Red Hat Linux on your system based entirely
on the automated installation routine. If this is the case, you can
move on to other chapters in this book. The rest of this chapter
covers some of the most important steps in setting up and installing a
Linux system in more detail. If you encounter problems during the
installation, or want to make changes to your configuration, you can
check the respective sections later in this chapter. For now, you can
take a quick look at each of the steps in the automated installation
process.
Choosing Text or Graphics Installation
Red Hat Linux gives you two choices for installation: text-based or
X-based. If you have installed Linux before or are familiar with
operating systems, you can use either with equal confidence. The
graphical interface installation using X is a more visually pleasant
installation process, and it is a neat aspect of Red Hat Linux.
On the other hand, the text-based installation process is more
traditional and familiar to veteran Linux users. If you are unsure of
how to use X, or not sure of your system configuration with respect to
mouse and video card, you should stay with the text-based
installation. It guides you through each step with full descriptions
on the screen.
Setting Up Your Hard Drive
If you have not set up Linux on your system before, or you need to
allocate partitions for Linux on your system, you will need to use a
disk-partitioning scheme. Red Hat Linux gives you a choice of two disk
partitioning utilities: fdisk and cfdisk. The fdisk utility is similar
to the DOS FDISK program. It is covered in more detail later in this
chapter, in the section entitled, "Installing the Linux Partitions."
The cfdisk utility is similar to fdisk but is a little more friendly.
Many people find cfdisk easier to use than fdisk, as it uses simple
mnemonic commands to perform each function. The choice of partitioning
utility is entirely up to you: they both do the same job.
If you have set new partitions on your hard disk for Linux, you will
have to reboot your system to make them effective (don't forget to
write the partition table to disk when you exit either fdisk or
cfdisk!). After a reboot, start the installation process again either
from your boot floppies or the CD-ROM, and the new disk partitions
will be recognized by Linux.
Formatting the Partitions
After the disk partitions are set, Red Hat will try to detect your
swap partition. The installation routine will display a window with
the device names of all your swap partitions listed. To format the
swap partition, choose one of the partitions listed (or the only entry
if you set up only one swap partition) and choose Yes from the menu to
start the formatting. The process takes about a minute, depending on
the size of the swap partition.
After the swap partition has been formatted and made available to the
kernel, the installation routine detects any Linux data partitions.
These are displayed with the option to format them. For a new
installation, you should format the Linux partition using this screen.
Setting Up Ethernet
During the swap and Linux data-formatting process, Red Hat asks if you
want to install Ethernet now. If you have an Ethernet card in your
machine and want to set it up while the installation process is
running, you can do so. If you don't have an Ethernet card or want to
delay the installation for later, that's fine, too; you can skip a few
steps.
If you elect to set up Ethernet now, you are asked for a machine name
and a domain name. After that, you are asked for the IP address of
your machine and the subnet mask (which is generated automatically and
probably doesn't need changing). A few other configuration settings
based on the IP address may be displayed. Again, the default settings
are fine for almost every system.
You will be asked if your machine uses a gateway. If you use a
separate machine to access the Internet or another network, answer
Yes. If you use a gateway, you will be asked for its identification.
You will also be asked if there is a nameserver to be used by this
machine. If your network has a DNS (Domain Name System) server that
performs IP address conversions, answer Yes and supply its
identification. Otherwise, answer No. You can always add a nameserver
later, after the system is up and running.
Setting Up the Mouse
After a message about the Metro-X server supplied with Red Hat Linux
and a selection of the type of graphics card to use (if in doubt,
select standard VGA or SVGA), you are asked for the type of mouse
attached to your system. Select the entry that matches the type of
mouse you use, or one that is compatible with your mouse.
You are then asked which device your mouse is attached to. In most
cases, the mouse is attached to COM1 (/dev/ttyS0) or COM2
(/dev/ttyS1). Select the proper entry. If you are not sure which port
your mouse uses, select COM1; it is the most common configuration.
Configuring X
If you have selected the X-based installation routine, Red Hat Linux
tries to determine your video system so it can start X. If you are
using the text-based installation routine, this process is skipped for
now.
In most cases, Red Hat Linux will try to set up the X system by
checking the type of video card you have. You will probably see a
message asking if you want the installation routine to "autoprobe,"
which means it will try to determine the type of video card and video
chipset installed on your machine. If you have a particular reason for
not autoprobing (some video cards will hang if they are sent the wrong
sequence), you will have to manually supply the configuration
information. If you are unsure whether or not autoprobing should be
allowed, let it go ahead and try. The worst that can happen (usually)
is that the system will hang and you have to reboot.
After autoprobing, the installation routine displays the type of video
chipset it found and the amount of memory it thinks is on the card.
For most systems, accept the defaults unless you know exactly what
type of chipset and on-board RAM you have.
After answering all the questions properly, X will start and you will
see the X-based installation procedure.
Selecting Packages to Install
Whether you are using X or text-based installation, you will see a
screen that lists all the packages on the Linux CD-ROM. You can select
which packages are to be installed during the setup process. You can
install as many or as few of these packages as you want. You can delay
the installation of many of them until later, if you want.
After selecting the packages to be installed, you will see a message
asking if you want to have individual package contents displayed for
selection. This lets you select only portions of the more generic
packages for installation. If you select this option, you will have to
wait by your screen and provide input at regular intervals. If you
want Linux to install all the components in a package, answer No to
this prompt and you can leave the system to install by itself.
After you have selected the packages to be installed, Red Hat's
installation routine will start installing the software. You will see
status messages on the screen as the process goes along.
Using LILO
After the installation process has formatted the drive partitions and
copied all the software packages you selected to the data partition,
you are asked if you want to run LILO to set up the boot system for
this drive. If you have a disk drive devoted only to Linux, or it is a
split DOS/Linux drive, you can run LILO and set the drive to boot into
either operating system.
If you are running another operating system, such as UNIX or OS/2, you
may elect not to use LILO and create a boot floppy instead. LILO is
covered in much more detail in Chapter 4, "LILO."
Boot and Root Disks
Even if you are installing from CD-ROM, you need three high-capacity
floppies (either 1.2MB or 1.44MB). These are a single-boot floppy and
two root (also called swap) floppies. The boot floppy holds the kernel
used to start Linux the first time. The root or swap floppies hold a
small file system that includes utilities needed for the installation.
In most cases, the boot and root floppies are copied from existing
files that are called images. The image is a precompiled version of
the system that you duplicate onto the floppies, eliminating the need
to start from scratch. CD-ROM and FTP distributions will have
directories for several boot and root images. You must select the
image that matches your hardware as much as possible, copy them to the
diskettes, and start your system with the diskettes.
You can do most of these steps from DOS, although you can't use the
DOS copy command to create the boot and root floppies. The floppies
must be created with a utility that ignores DOS formatting. This
utility, commonly called RAWRITE.EXE, is included with most Linux
software distributions.
Selecting a Boot Kernel and Root Image
The Red Hat Linux CD-ROM has a directory under the root directory
called images which contain the boot and root images. You should run
DOS either from a floppy or a partition on your hard disk to examine
the CD-ROM. If you are copying your files from an FTP site, you can
select the boot and root images you need while connected to the remote
FTP machine and transfer only the images you need to your local
machine.
The types of boot kernels usually available are described in a file in
the kernel image directories. The Red Hat Linux CD-ROM accompanying
this book has a number of directories under the images directory:
* 1213—Contains the standard boot images
* 1357—Contains experimental boot images with a new kernel
* custom—Contains boot-disk images of a specialized nature
Under the images directory there is also a directory called floppies,
which contains mirror images of the floppy distribution set for Red
Hat Linux. Among the three subdirectories that hold images, there are
many hundreds of images. If you are not familiar with Linux or don't
want to play around with special kernels and hardware configurations,
stick to the 1213 directory. It has boot images that will handle most
systems.
In the \images\1213 directory there is a file called IMAGE.TXT, which
lists the makeup of each image. A typical entry looks like this:
image # 0021:
SCSI : Adaptec, Buslogic
Ethernet: SMC
CD-ROM : IDE/ATAPI or SCSI
For each image in the 1213 directory the IMAGE.TXT file lists the
image name (the file for the preceding entry is called BOOT0021.IMG),
the type of controller card used for the disk drives (a SCSI
controller made by, or compatible with those by, Adaptec or Buslogic),
the type of Ethernet card (SMC in this example), and the type of
CD-ROM drive on the system (an IDE or SCSI CD-ROM drive, in this
case).
After you have selected the proper image that most closely matches
your hardware setup, you can copy it to a floppy. You will also need
the two root-disk images, which are in the \images\1213 directory as
RAMDISK1.IMG and RAMDISK2.IMG. If you choose the boot image
incorrectly, don't worry. All that will happen is you won't be able to
install Linux, and you can start the process again.
If you obtained your boot and root images from an FTP or BBS site, the
files may be compressed and archived. If they are, they will end with
the file type .gz. Before you can install the images to a floppy, they
must be uncompressed with the gzip utility.
Creating the Boot and Root Floppies
You can create the boot and root floppies either from DOS or from a
running UNIX or Linux system. If you don't run DOS yet, or don't have
a DOS boot disk, you will have to use another machine to create the
floppies. Because the DOS-based floppy creation is the most common, we
can deal with it first. This uses a utility called RAWRITE.EXE, which
is included on the CD-ROM in the \DOSUTILS directory.
To create the boot and root floppies, you must use a utility program
to write the image to diskette. If your image files are compressed
(they will have a .gz) extension, they must first be uncompressed with
the gzip utility. If you are working from CD-ROM, you will have to
copy the files to a DOS hard disk since you can't write the
uncompressed image to the CD-ROM. To uncompress a .gz file, issue the
command
gzip -d filename
where filename is the name of the compressed file (including the .gz
extension). The -d option tells gzip to decompress the file. When it
is completed, the .gz file will have been erased and only the
uncompressed file will remain (with the same filename, less the .gz
extension). You should uncompress the boot and root images.
The three floppies you need for Red Hat Linux don't have to be blank,
as the RAWRITE utility used to copy the image to the floppies doesn't
respect DOS formatting conventions. The two floppies must be high
density. The disks must be formatted using the DOS format program. The
boot diskette must be the correct size for your system's boot floppy
drive (A: in DOS terms).
To use the RAWRITE program, enter its name at the DOS prompt with the
full path to the utility, such as:
D:\DOSUTILS\RAWRITE
if your CD-ROM is drive D (or you can copy the files to a directory on
your hard disk). RAWRITE will prompt you for the name of the file to
copy and then destination drive letter. RAWRITE will then copy the
images. Label the disks when the process is finished.
If you have access to a UNIX or Linux system, you can create the boot
disks from within that operating system. You will need to put the
image files on the UNIX or Linux system and use the dd utility to copy
them to floppy. First, make sure the images are uncompressed (no .gz
extension). If they are not, uncompress them with the gunzip utility.
To uncompress files in UNIX or Linux, issue the command
gunzip filename
where filename is the name of the image file, with its .gz extension.
The gunzip utility will erase the compressed file and leave an
uncompressed version in its place.
To copy the images to a floppy, you need to know the device name of
the floppy within the operating system. For most systems, the first
floppy drive is /dev/fd0 and the second floppy drive is /dev/fd1.
(Some systems treat the floppy drives as a raw device, which have the
names /dev/rfd0 and /dev/rfd1.) Copy image files to the floppy with
the command
dd if=filename of=/dev/fd0 obs=18k
where filename is the name of the uncompressed image. The dd command
converts file formats. The if and of parts of the command indicate the
input and output filenames or devices. The obs portion of the command
indicates the output block size (in this case, 18KB).
For example, to copy the BOOT0023.IMG image to the first floppy
(3.5-inch 1.44MB), issue the command:
dd if=boot0023.img of=/dev/fd0 obs=18k
If you already have a Linux system, an easy way to make the boot and
root floppies for Red Hat Linux is with a utility supplied on the
CD-ROM. There is a Perl program called MKFLOPPIES.PL in the IMAGES
subdirectory that can do the entire task for you. A series of
questions will help you determine the proper images.
Partitioning the Hard Disk
Hard disks are divided into partitions or areas dedicated to an
operating system. A hard disk can have up to four primary partitions,
with some partitions being further divided into more logical drives by
the operating system software.
Linux prefers to have two partitions: one for the Linux swap space,
and one for the Linux software file system itself. The swap space is
used as an extension of your machine's physical RAM and can be quite
small. The Linux file-system partition tends to be quite large, as it
must hold all the Linux software. You can have several Linux
file-system partitions, although one must be designated as the boot
partition (where the kernel and primary utilities are located).
If you are using an existing hard disk that has an operating system
already installed on it, you will have to repartition your hard disk
to make room for Linux. This tends to be a destructive process,
meaning that anything on your hard disk will be destroyed. Make
backups of your existing data if you want to keep it!
Partitioning of a hard disk is done with the fdisk utility from DOS or
Linux, or interactively during the Red Hat Linux installation. You
don't need to partition the drives before installing Red Hat Linux,
but if you do partition during the installation routine you will have
to reboot to make the changes effective. If you have used fdisk in
DOS, the Linux version does the same task (although the menus are
completely different and much more complicated). Many PC-based UNIX
systems also use fdisk to partition hard drives.
______________________________________________________________
NOTE: A DOS utility called FIPS sometimes allows nondestructive
changes to your partitions, assuming no data is on the areas that
will be repartitioned. FIPS is available from many sources,
including most of the Linux FTP sites and some Linux CD-ROMs.
However, you should make backups, just in case!
______________________________________________________________
You must decide how much space to allocate to the different partitions
before you start, as changing your mind later will mean destroying all
the data you have saved to disk. The Linux swap-space partition size
will depend on the amount of RAM in your system, the number of users
you expect, and the type of development you will do.
If you are going to maintain a DOS partition on the same disk, you
will have to balance the disk-space requirements of both operating
systems against your total disk capacity. A minimum Linux file-system
partition will be about 20MB, although closer to 200MB is needed for a
full X-based installation.
Linux Swap-Space Partition
How big should the swap-space partition be? No single number works for
all installations, unfortunately. Generally, because the swap space is
used as an extension of physical RAM, the more RAM you have, the less
swap space is required. You can add the amount of swap space and the
amount of RAM together to get the amount of RAM Linux will use. For
example, if you have 8MB of RAM on your machine's motherboard, and a
16MB swap-space partition, Linux will behave as though you had 24MB of
total RAM.
Linux uses the swap space by moving pages of physical RAM to the swap
space when it doesn't need that page at the moment, and vice versa
when it needs the memory page. So why not make a very large swap space
and let Linux think it's in heaven? Because the swap space is much
slower in access time than RAM, and there is a point at which the size
of the swap space acts against your Linux system's efficiency, instead
of for it.
Swap space may not be needed if you have lots of RAM. For example, if
you have 16MB of physical RAM and don't intend to do any application
development or run X, you won't make much use of the swap space
because Linux can fit everything it needs into the 16MB. (You still
should have a small swap space, just in case.)
If you are running X, developing applications, or running memory-hog
applications like databases, swap space is crucial even if you have
lots of physical RAM. Even 16MB RAM is not enough for X, so you need
swap space.
A good rule is to create a swap space with a size of 16MB. Unless you
have a very small capacity hard disk, this won't be a major drain on
your resources and it does give Linux plenty to work with. If you
don't want to allocate this much space, a good rule is to have a total
of 16MB RAM (swap space plus physical RAM). Don't eliminate the swap
space completely, though, unless you really have a lot of RAM. At a
minimum, set up a 4MB swap space. Running out of RAM can cause Linux
to totally lock up or crash, which isn't a pretty sight!
Setting Up Partitions
Because the versions of fdisk in DOS, OS/2, UNIX, and Linux all
differ, all the steps aren't explained here. The fdisk utility is very
easy to use, so if you have used PC machines for a while this will not
be a problem for you. Remember, though, that fdisk will destroy
existing data on your disk! You can set up your Linux disk partitions
either from DOS or from within Linux. It really doesn't matter which
approach you use, although the DOS fdisk program is a little easier to
use than the Linux version. If you are using DOS fdisk to repartition
a DOS area on your drives, you may as well use it to set up the Linux
swap space and file-system partitions, too. The DOS version of fdisk
has one problem, though: it can't set the partition type numbers.
Linux's fdisk lets you set the partition types to be recognized more
easily (type 82 for Linux swap and type 83 for Linux data).
To set up partitions for Linux, remove any existing partitions first
(unless you want to keep them as they are). If you intend to use DOS
on the same system as Linux, DOS should be the first partition on the
disk so it can boot. (There are a few ways to get by this using LILO,
but it is still a good rule to leave DOS as the first partition.) If
you are keeping an existing DOS partition, it should be the first
partition.
You should create a DOS boot disk that can reformat and transfer the
DOS kernel to the hard drive, regardless of whether you are leaving an
existing DOS partition or creating a new one. To create the boot
diskette, use the DOS command
format a: /s
(assuming A: is the drive the diskette is in). The /s option transfers
the operating system kernel. Next, copy the utilities FDISK, FORMAT,
SYS, and CHKDSK to the boot floppy. You should also copy an editor,
such as EDIT, and your existing CONFIG.SYS and AUTOEXEC.BAT files
(although you could rename them). This disk will let you format any
new DOS partitions. Alternatively, if you are starting from scratch
with a new DOS partition, you can simply reload DOS from the original
diskettes when ready to format the DOS partition.
If you are removing an existing DOS partition and re-creating a
smaller one (as you would if your entire disk was DOS before Linux
came into your life), follow these steps (after making a backup of
your DOS data):
1. Remove the existing DOS partition.
2. Create a new primary DOS partition as the first partition.
3. Make the DOS partition active.
4. Reboot the system from your boot floppy (or DOS disks).
5. Format the DOS partition and transfer the DOS kernel (COMMAND.COM)
and hidden .SYS files by using the DOS SYS command or using FORMAT
/S.
6. Restore your backup files to the DOS partition (this can be done
at any time).
Next, set up the Linux swap-space partition by creating a partition of
the proper size. You can do this step either from DOS or when you have
booted Linux from the boot and root floppies. For the sake of this
chapter, we'll assume you are setting up the partitions from DOS
(although the process is the same either way).
Most versions of fdisk enable you to enter the size of the partition
in MB, with the utility calculating the sector numbers that apply to
it. Set the size of the Linux swap space to whatever size you decided.
Don't make the partition active or format it! You can set up the
swap-space partition in an extended disk partition, but a primary
partition is a better choice if your disk can support it.
Finally, create the Linux file-system partition to be whatever size
you want, or the rest of the disk if that's the only partition
missing. Again, don't activate or format the partition. When you are
running the Linux installation routine, you will identify and format
the swap space and file-system partitions properly.
Install the Linux Partitions
One of the first steps you are asked to do by the installation routine
is to set up disk partitions. Red Hat Linux has two disk-partitioning
utilities: fdisk and cfdisk. Both perform the same tasks, but cfdisk
is a little easier to use. The fdisk utility, though, will be familiar
to users of other Linux versions.
If you have more than one hard drive, you can place your Linux
partitions on either drive. If you are planning on keeping a DOS
partition, though, make sure it is the first partition on the first
drive. Linux isn't so picky. If you want to boot Linux cleanly, place
a Linux file system on the first drive. You can also create Linux file
systems on the second drive. Linux swap partitions can be on either
drive. If you have two drives, putting the swap space on the second
drive and the bootable Linux data partition on the first should
provide better performance.
Linux's fdisk
Linux's fdisk program is different from the one in DOS, so you should
check the menus frequently to determine the proper commands. During
the installation process the disk partitions are detected
automatically, and you are placed in the fdisk program.
Alternatively, you can run fdisk at any time from a Linux prompt. You
invoke the Linux fdisk in the same manner as that in DOS. If you don't
specify a drive, fdisk will assume the first one in the system.
Otherwise, you can specifically indicate which disk drive to partition
by giving the device name on the command line, as in
fdisk /dev/hdb
which will invoke fdisk for the second drive. If your system has IDE,
ESDI, or RLL drives, the first is /dev/hda and the second /dev/hdb.
SCSI drives are /dev/sda, /dev/sdb, and so on. Because seven SCSI
drives can be supported on a single controller, you could have up to
/dev/hdg. (You can go even higher with another controller card, but
few Linux systems will require this!)
As mentioned previously, Linux fdisk commands are different from the
fdisk commands for DOS. Essentially, the commands you need to run the
Linux fdisk utility are the following:
* d—Deletes an existing partition
* l—Lists all known partition types
* n—Creates a new partition
* p—Displays the current partition table
* q—Quits fdisk without saving changes
* t—Changes a partition's type code
* v—Verifies the partition table
* w—Writes current partition table to disk and exits
The process for setting up a partition is to first examine the
partition table to make sure any existing partitions are correct. If
you have a DOS partition on your drive, it should show in the
partition table. If you created Linux swap and file-system partitions
when you were in DOS's fdisk, they should appear in the partition
table too, although the partition types will be incorrect.
Setting Up Linux Partitions
To create the Linux swap space, use the n command and give the
starting sector number. Usually, this will be immediately after any
existing DOS partition (or other operating systems you have
installed). Linux's fdisk lets you specify the size of the partition
either by supplying an end sector number or by giving a size in MB.
The latter is much easier to work with, so just enter the number of MB
you want to set your Linux swap-space partition to. The format is
usually +XXM, where XX is the number of megabytes (such as +16M). You
can also specify kilobytes, but you don't want to create a swap
partition that is less than 1MB in size.
______________________________________________________________
NOTE: Most PC BIOSs cannot handle more than 1024 cylinders on a
disk drive. You may not be able to create DOS or Linux partitions
or file systems that go beyond the 1,023th cylinder (numbering
starts at zero). Some other operating systems, such as SCO UNIX,
enable you to use anything beyond the 1,024 limit. Linux can use
partitions beyond the 1,024 limit, but it can't boot from them. If
you have a disk drive that has more than 1,023 cylinders, make sure
your primary Linux partition ends before 1,023. You can create
extra partitions following that cylinder and mount them as second
file systems.
______________________________________________________________
The fdisk program will ask you if you want to create a primary or an
extended partition. If you are creating a primary partition it wants
the number (one to four—remember a DOS partition has to be number
1 to boot). In most cases you should create only primary partitions,
unless you have a large disk drive. Extended partitions can be used to
add logical drives inside them, as DOS creates logical drives. In
Linux, extended partitions are not the same as extended file systems!
After you have created the Linux partition, you should assign its
type. Some versions of fdisk prompt for this right away, whereas
others let you select the option to assign file-system types from the
fdisk menu. In either case, the letter l will display all known
file-system types. Choose the one that designates a Linux swap space
(number 82), and check the partition table. Your Linux swap-space
partition should have the correct size and partition type displayed.
Actually, Linux doesn't care about the partition-type numbers and
ignores them completely, although it can make autodetection of the
Linux partitions a little easier during installation. Some other
operating systems do note them, though, so it's a good practice to
label them correctly to prevent future problems. It also helps you
keep the partition table nicely organized!
Next, create your primary Linux file-system partition in the same
manner. If you want to use the rest of the disk drive for that
partition, you can enter the end sector number of your drive (Linux's
fdisk will tell you the range you can use). This would be the usual
default if your hard drive has a DOS, Linux swap space, and Linux
file-system partition on it. After you have created the Linux file
system, you should identify its file type as 82, which is a "Linux
native" type.
You should note the size of the swap-space and file-system partitions
in blocks; you will need this information later. You can read this
straight from the partition table.
After you've created the Linux partitions and are satisfied with the
partition-table layout, save and exit fdisk. If you don't save the
information, you will have to repeat the process again.
Enabling the Swap Space For Installation
When you have set up the disk partitions through the automated
installation routine, you don't have to worry about enabling the swap
space; it is performed automatically. If you are doing these steps
manually, you will have to enable the swap space so Linux can use it.
If you have 4MB of RAM or less, you will have problems installing
Linux unless you have the kernel use the swap space. (If you have only
4MB or less of RAM in your system, you should have a swap space of at
least 8MB—preferably 16MB.) If you try to install Linux and get
memory error messages, it's because there is not enough RAM and the
swap space is needed.
______________________________________________________________
NOTE: If you've turned the swap space on and still get error
messages, you need either more physical RAM or a larger swap space.
To increase the size of a swap-space partition, you may have to
remove the existing Linux partitions and re-create them with fdisk.
______________________________________________________________
If you have a small amount of RAM, you should enable the swap space to
help the installation process. Even if you have lots of RAM, there's
no reason not to enable the swap space now, anyway. To enable the swap
space, issue the command
mkswap -c partition size
where partition is the name of the partition and size is the size of
the partition in blocks. You may have noted this number earlier when
setting up the partition table. If not, you can start fdisk again and
read the size in blocks from the partition-table display.
For example, if you have set up the Linux swap space on partition
/dev/hda2 (the second primary partition on the first non-SCSI drive)
and it has a size of 13,565 blocks, you would issue the command
mkswap -c /dev/hda2 13565
The -c option in the command line tells the mkswap utility to check
for bad blocks in the partition. If this option is on, it will take a
little longer to create the swap partition; however, a bad block in
the swap partition can cause your entire system to crash, so it's
worth the delay. If mkswap finds any errors in the swap space, it will
generate an error message. However, because mkswap flags bad blocks to
be left alone, you can ignore the messages unless there are a
considerable number of them, in which case your hard drive has too
many bad blocks!
When the swap partition has been formatted, you enable the Linux
swap-space partition with the command swapon. Usually you will have to
specify the partition, although some versions can figure the partition
out automatically from the partition table. It never hurts to be
explicit, though. To enable the swap partition just formatted, enter
the command
swapon /dev/hda2
You will have to repeat the format and swapon commands for each swap
partition, if you created more than one. As soon as the swapon command
is executed, the Linux kernel will start to use the new swap space as
an extension of the physical RAM.
Creating the Linux File-System Partition
When you have a swap space configured and working, you can set up the
Linux file system. This step may be automated by some Linux
installation scripts, or you may have to execute it yourself. Either
way, this section explains what is going on.
You will have already allocated the partition table to support a Linux
file system. Now you can create the file system with the mkfs (make
file system) command. The exact format of the command depends on the
type of file system you are setting up. The most popular file system
(for reasons of speed and flexibility) is called the Second Extended
file system (which has nothing to do with extended partitions on a
hard disk). To create a Second Extended file system, issue the command
mke2fs -c partition size
where partition is the device name and size is the size of the
partition in blocks (taken from the partition display in fdisk). The
size doesn't have to be specified with mke2fs as it can figure it out
from the partition information. For example, to create a file system
in /dev/hda3, the command would be
mke2fs -c /dev/hda3
______________________________________________________________
NOTE: When specifying the size of a partition, make sure you use
blocks and not sectors or cylinders. Using the wrong value will
result in errors or only a fraction of your partition being used.
______________________________________________________________
The mke2fs utility will check the partition for bad blocks (the -c
option) then set the file system up properly in that partition. If you
are setting up a large partition, the disk check can take a few
minutes—but you should not ignore it unless you know your disk is
good.
The other file systems available to Linux are the Xia file system, the
Extended file system, and the Minix file system. The Xia file system
is good, but not as popular as the Second Extended. The Extended file
system is an older version of Second Extended, whereas the Minix file
system is compatible with the old Minix operating system. You can
create these file systems with the following commands:
* Extended—mkefs
* Minix—mkfs
* Xia—mkxfs
All three commands take the same arguments as the Second Extended
file-system command. The Minix file system is limited to 64MB.
None of the mkfs commands format the filesystem—they simply set
it up. You are prompted for a file-system format during the
installation process.
Troubleshooting
There are many different problems that can occur while setting up and
installing a Linux system, although most of them will be
self-explanatory from error messages. A few commonly encountered
problems can be easily dealt with, though, so we'll look at them
briefly.
Software Installation
You may encounter a few errors when installing Linux. If you get the
message device full, it means you have run out of disk space and need
to install fewer components or allocate more hard disk space. If you
haven't installed the basic system, you will need more disk space. You
will have to delete your partitions and start the installation process
again, allocating more 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
floppies, and they tend to indicate a bad diskette. All you can do in
most cases is replace the diskette with a new one.
Hard Disk and Disk Controller
When Linux boots it displays a few messages, one of the most important
being a partition check. You will see messages like this:
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 will probably be different,
of course. If you don't see any partition information, either the hard
disk controller is not recognized properly, or the disk drives
themselves are not accessible. There are a number of potential causes
for these problems, including the obvious:
* 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).
* Confirm that the power connector is attached to each disk drive.
Without power, your drive won't spin up and Linux can't touch it.
* Check the partition table to make sure you created a Linux
partition properly.
After that, if the drive is not working properly with Linux but works
fine when you boot DOS, a kernel driver for the hard disk is probably
at fault. Some IDE drives, for example, are not as well-behaved (that
is, 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.
Device Conflicts
One of the most commonly encountered problems is hardware not
recognized properly. This can happen to a CD-ROM, a network card, and
even a hard disk. Most of the time this is caused by a conflict in the
IRQ (interrupt), DMA (Direct Memory Address), or I/O address settings.
When two devices have the same settings on any one of the 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 on the boot messages. When Linux boots
up, it generates verbose messages on the console 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;
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, you can run a diagnostic utility under DOS
such as MSD or Norton Info. Windows 95 users can use the System icon
in the Control Panel to obtain this information. These diagnostics can
show you the current IRQ, DMA, and I/O addresses and pinpoint any
conflicts. They can also be used for finding available settings.
Alternately, you will have to check the settings of every device in
your system for conflicts. Usually, network cards will 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 if
the boot process moves past the device that caused the hang-up.
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 were compiled with settings that are default
values for adapters or disk drives; if the settings have been changed,
the kernel will hang up. This is often the case with special-purpose
kernels that have been developed for non-mainstream adapters. To check
for this type of problem, you should investigate any documentation
that came with the kernel image.
The most common devices in a PC (COM ports, parallel ports, and
floppies) and their IRQ, DMA, and I/O addresses are shown in Table
3.1. 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.
Table 3.1. Common IRQ, DMA, and memory address settings.
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
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, you should check your device or
card-installation manual for recommended values and potential
conflicts.
SCSI Problems
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.
Table 3.2 lists many of the common SCSI errors and their probable
causes. Find the message that closely matches the error message Linux
displays in this table to determine your corrective steps.
Table 3.2. Common SCSI problems and their solutions.
Problem Probable Solution
SCSI device at all possible IDs One or more devices are at the same
SCSI ID as the controller. Check and change device IDs. Controllers
should be ID 7.
Sense errors Probably caused by bad termination. Check that both ends
of the SCSI chain are terminated. If that is not the problem, the
cable is likely at fault.
Timeout errors Usually caused by a DMA, IRQ, or I/O-address conflict.
See the preceding section for more information.
SCSI adapter not detected The BIOS is disabled or the SCSI adapter is
not recognized by the kernel. Check the drivers.
Cylinders Beyond 1024 Your disk has more than 1,024 cylinders, which
the PC BIOS can't handle. Linux can use more than 1,024 cylinders, but
it can't boot from a partition that extends across that cylinder
boundary.
CD-ROM drive not recognized Some CD-ROMs require a CD in the drive to
be recognized properly. Insert a CD and reboot.
Booting Linux
If you have installed Linux and the system won't boot properly from
your hard disk, it may be a problem with LILO or with the partitions.
If you created a boot floppy, boot from that. If that boots without a
problem, check the partition table by executing fdisk. Make sure the
Linux partition is active. If it is and you still can't boot from the
hard disk, boot from the floppy and run LILO again to configure the
boot sector. See Chapter 4 for more information on LILO.
A problem will sometimes occur when Linux can't find the main Linux
partition. Boot from the floppy and hold down Shift or Ctrl. This
produces a menu that enables you to specify the boot device
explicitly. This problem can usually be corrected with LILO.
Summary
Much of this chapter will be familiar to you if you have installed
Linux before, although some users really don't know what goes on
during the automated installation script. Knowing the process, and
staying on top of it, helps prevent problems with the Linux
installation.
The next step is using LILO to properly configure the boot
system—a commonly misunderstood and misused process. The next
chapter looks at LILO.
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Enjoy Linux!
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