hardware

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.
• Thats 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 manufactures. 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 dont 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 area is called a partition.
• An empty disk will have no partitions.
• You will have to set up partitions before working
  with a disk.
• Changing the partitions at a later stage will,
  generally, make the data on the disk inaccessible.

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/isorecorder.htm
  
• http//www.cdburnerxp.se/downloadsetup.php
• 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
  downloading a ton of software we dont need.
• Do not select desktop environment. This is
  particularly wasteful for what we are trying to
  do.