hardware

Thomas Krichelhttp://openlib.org/home/krichel

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.

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.

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

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

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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/

isorecorder.htm http://www.cdburnerxp.se/

downloadsetup.php Use it to burn.

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.

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

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)

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.

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.

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”.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.