hardware related info

1. hardware
Thomas Krichel
http://openlib.org/home/krichel

2. introduction

This is a basic introduction to computer
hardware.

I wrote it from memory.

It contains the things I know about without
having to look them up.

That's about how much you need to know.

3. basic components

basic components are

processor

memory

motherboard

input/output devices
− disks
− network interfaces

The first three, plus the bus speed, are
essential to the understanding of the
performance of the computer.

4. processors

The processor does all the calculations on a
computer.

The performance indicator of the processor is
the frequency of operations.

There are various types of processors, by
different manufactures.

Intel

AMD

5. architecture

The Debian operating system offers a complete
range of software that can be run with a range
of processors by a certain manifactures. Such a
range of software packages is called an
architecture.

We use the i386 architecture for Intel
processors.

AMD processors may be more open source
friendly

6. memory

The memory is where all data that the computer
works with is stored.

If the memory is small the computer has to
perform more operations to read and write data
to the disk.

As a consequence, it will appear to be slower.

7. motherboard

This is a green sheet of plastic that all
components inside the computer attach to.

We don't need to know more about it, just the
plane concept will do.

8. devices

These are things that the computer uses for
input and output of data.

Examples include

keyboard

screen

network card

disks

We only need to study disks and network cards.

9. disks

There are three architectures of disks

IDE, aka PATA, an old system

SCSI, a bit more modern

SATA, used in most modern systems

We need to be aware of them because the way
that Linux refers to them.

10. IDE

When a computer can use IDE, you see two
forty-pin connectors on the motherboard.

These are the primary and the secondary IDE
channnels. They are usually labelled.

To each channel, you can attach two disks.

One is called the master.

The other is called the slave.

11. master and slave

One method to select master and slave is to set
jumpers on the disk. The position of the
jumpers is often written on the disk. Otherwise

The other method is called “cable select”. There
you place the master at the end of the 40 pin
IDE cable.

12. device names

Linux needs to give the devices names in other
to talk to them.

The device names for IDE are

/dev/hda for the primary master

/dev/hdb for the primary slave

/dev/hdc for the secondary master

/dev/hdd for the secondary slave

13. SCSI and SATA

SCSI and SATA drives are named

/dev/sda

/dev/sdb

etc.

Usually it is a bit of guesswork to know which
drive is give what name. There may be a better
way than guesswork, but I don't know about it.

14. file systems

A file system is a way to set up files on a disk.

Common file systems are

Microsoft FAT

ext2 or ext3, used in Linux

Reiserfs, used on Linux

Linux kernels support various file systems
natively, including Microsoft file systems.

15. several file systems

If you have several file systems on a disk, each
system needs to occupy a separate physical
area on the disk.

Such an aera is called a partition.

An empty disk will have no partitions.

You will have to set up partitions before working
with a disk.

Chaning the partitions at a later stage will,
generally, make the data on the disk
inaccssible.

16. partition table

Any disk has a special place for the partition
table.

The partition tables says

what partitions are on the disk,

where each partition starts and end

Changing the partition table makes all data on
the disk unusable.

17. default partitions

On a Linux system, if you only have one disk on
a computer, it is customary to have two
partitions on it.

the main data partition

the swap partition

Deciding on the size of both is a bit of black
magic. There is no hard rule.

We let the Debian installer do it for us.

18. device names with partitions

If you have a device that linux calls foo, the first
partion will be foo1, the second partition will be
foo2 etc.

Thus you can have /dev/hda1, /dev/sdb3 etc.

The command “df” will list all devies and all
partition.

19. the main data partition

This is where you have all the data on the hard
disk.

This is usually formatted with the ext3 file
system.

There other file systems one could use, but this
is the default, one and we will use that one.

20. the swap partition

The swap partition is used to reserve space for
swapping.

Swapping is a way for a computer to work with
large memory requirements by writing parts of
the memory on the disk.

When this happens the computer appears to be
very slow.

21. initial setup

When the debian installer sets up your
machine, by default it will take the first disk.

Then it will calculate a partition table

swap partition

data partition

it will present you with the suggestions.

When you accept them, it will write the partition
table. All data on the disk will be lost.

This is the only time you should not accept the
default option.

22. booting

When you switch on a computer, you see some
messages.

They usually refer to particular pieces of
hardware that just tell you “hi, I am here in this
computer.

Then the operating system starts.

But before it starts, there is one interesting
stage.

23. more on initial setup

When we start the computer, it reads an
internal, essentially read only piece of data
known as the BIOS.

The BIOS has a number of settings. You can
make changes to them.

How to do that depends on the BIOS
manufacturer but there are some generic
features.

24. getting into the BIOS

When the machine starts, you see, maybe for a
second a message “press foo to enter setup”.

foo is usually the name of a key.

When you see this message, press the key
very quickly several times.

(yes, this presumes you have a working
keyboard attached).

You arrive in a menu-driven system.

25. the BIOS menu system

The menu system is usually in English.

It usually relies on keyboard strokes.

What keys do what depends on the BIOS
manufacturer.

What entries there are depends on the
manufacuturer.

We only need to know one BIOS setting, and it
is useful to know about another.

26. BIOS setting: boot sequence

When the machine boots, it looks for an
operating system on a sequence of devices.

That sequence is called the boot sequence.

When we install Debian, we need to make sure
that the medium that contains Debian is in the
boot sequences.

We also need to make sure that this medium
appears before any other medium that contains
an operating system.

27. BIOS setting: boot on power

When you are running a server machine, you
want the machine to be on all the time.

After a power cut, you want the machine to boot
as soon as power is restored.

There usually is a BIOS setting for that.

28. making a Debian medium

Go to the debian installer http://www.debian.org
/devel/debian-installer/

I made a copy of the current CD for you at
http://wotan.liu.edu/opt

Get software to burn the CD

http://isorecorder.alexfeinman.com/isorecord
er.htm

http://www.cdburnerxp.se/downloadsetup.ph
p

Use it to burn.

29. working with the installer

The only rule is: don't panic.

Any decision you are making when working
with the installer can be reversed quite easily
later.

The only exeption is the disk partitioning,
reversing that would be cumbersome.

30. overall steps

boot

set up user interface of installer

setting up network (the crucial part)

setting up a disk

setting the time

setting up users

downloading basic software from the network

making system bootable

31. obvious sequence

At the start, select the normal (not the graphical
installer) and press enter.

Select the language of installation (English)

Select your country (United States)

Select your keyboard layout (US)

32. the hostname

This is a short name for the machine.

Here any name can be used. The name can't
contains a space. You need to let me know
about the name.

Don't use the name debian because I want
everybody to have a different machine name for
ease of administration of the course.

33. network configuration

The installer will configure the network with the
help of a protocol called dhcp.

This should work in the class situation.

I will discuss networks later, so I skip over
details for now.

If the dhcp we have a serious problem.

34. the domain name

Here you should enter a domain that you own
and control.

If you don't have one, or don't know what this is
please enter the domain of a friend who will run
the domain for you.

Since Thomas is your friend, enter his domain
here: “openlib.org”.

35. disk partitioning

Here chose of guided partitioning, using the
built-in partitioner.

Select the disk to partition, usually there is only
one.

Choose the default of all files in one partition.

Accept the partition that is proposed.

Then you get the screen where you are warned
you will loose all data, here don't accept the
default to tell the partitioner to go ahead.

36. setting up time

The time can be set in the BIOS. They BIOS
calls a battery that keeps running. But that is
not reliable.

Modern linux machines get the time from the
network from time servers. The time servers
know what time it is.

Then all you have to do is to set the time zone
you are in. Since you have said you are in the
US, you will be shown a list of US time zones.

37. setting up the root user

There is one superuser who has the right to do
anything on the machine.

The name of this user is “root”.

There is a sequence screen that invites you to
set the password for that user.

Since it is not echoed, you need to type it twice
to try to make sure that it was entered properly.

38. ordinary user

Although this is not strictly necessary, the
installer also requires the setup of an ordinary
user.

Here you first enter your full name, then your
user name (login name, no spaces, no
uppercase) and then your password.

39. network download

On the network, there are mirrors of Debian
that contain newer versions of the Debian
packages. It is a good idea to use the closest
mirror available. Say yes to use a network
mirror.

The mirrors are organized by country. Select
country and then select a mirror that appears to
be close. For class select any because we may
have a problem if all select the same.

40. http proxy

To download packages from mirrors, the
installer uses the http protocol.

This is a well-know protocol used to transfer
files on the web.

In certain, rare settings, a network administrator
may require you to use the http proxy. We don't
have such a requirement, so we can leave this
screen blank.

41. popularity contents

This is a bit of an oddity.

There is a contents on which packages are
most popular.

Machines participating in the contest report
what packages are installed on them.

You may elect to take part or not.

42. the bootloader

To make the system bootable without the CD,
Linux installs a special command sequence on
the hard disk you are installing linux to.

This special command sequence calls a
software known as a boot loader. The boot
loader shows you a menu to ask you what
operating system you want to load.

43. removing media

You need to remove the media you booted
from, or change the BIOS not to boot from it
again.

If you use a CD to install from the installer will
eject the CD for you.

Then the machine reboots.

You are done.

44. linux boot loaders

In olden days, people use lilo, the linux loader.

Nowadays people use the grub, the grand
unified bootloader.

Here you just have to follow the default to install
the bootloader.

45. collection of software

This is important. There are collections of
software predefined by the installer for certain
tasks a machine should do.

Here you should ONLY select the “standard
system”.

Selecting others, you will waste your time
dowloading a ton of software we don't need.

Do not select “desktop environment”. This is
particularly wasteful for what we are trying to
do.