Download Computer systems administration TE2003 Administration av

Computer systems administration
TE2003
Administration av datorsystem
TE2003
7th January 2008
09:00 – 13:00
IDE, Högskolan i Halmstad
Examinator: Magnus Jonsson, IDE-sektionen
Course Responsible: Kristoffer Lidström, IDE-sektionen tel. 16 73 85
Grades:
25p => 3
33p => 4
42p => 5
Number of questions: 15
Maximum points:
50
Number of pages:
2
No extra materials (calculators, books etc.) are allowed
Kom ihåg:
• Skriv namn på varje blad
• Numrera bladen
• Numrera svaren tydligt, siffra och ev.
bokstav, t.ex. 7 a)
• Svara på frågan. Tänk på att många
poäng kräver längre svar och få
poäng kortare svar. Om du skriver
ovid-kommande eller felaktiga
uppgifter i svaret kan det bli
poängavdrag på den frågan.
• Svara antingen på svenska eller på
Engelska
Lycka till!
Remember:
• Write your name on each sheet of paper
• Number the sheets
• Number your answers clearly, number
and possible letter, e.g. 7 a)
• Answer the Question. Many points will
demand a longer answer and few points
a shorter. If you answer with
irrelevant or erroneous information,
points may be deducted on that
question.
• Answer either in English or in Swedish
Good luck!
Written Exam, 7th January 2009
Computer Systems Administration TE2003
1. What are the main differences between the design of server computer systems for
datacenters when compared to a standard desktop PC? (I.e. are some problems
different/more difficult for one type of system when compared to the other?)
(3p)
Examples: Cooling and power use becomes and issue in datacenters. Also
redundancy and fault-tolerance is prioritized due to higher demands on
availability. On the other hand consumer products like PC’s pay more attention to
aesthetics, price.
2. The transistor is faster, more reliable and more efficient than its predecessors
vacuum tubes and relays. Another advantage is the possibility to use the transistor
in integrated circuits (IC).
a. What is an integrated circuit (IC) and what are its advantages over discrete
components?
b. Gordon Moore made an observation about transistors and ICs that has
come to be known as “Moore’s law”. What does this law state?
(5p)
a) An IC is a number of semiconductor devices (transistors, diodes, etc) integrated
onto a single chip. This integration allows for a higher density of devices per area
and avoids problems related to packaging and connection of individual devices.
I.e. lower cost/device, higher reliability, reduced power consumption. 3p
b) Moore’s Law states that the number of transistors on a single chip will increase
exponentially as a function of time. 2p
3. When working with electronic components and computers there are some safety
rules that should be followed in order to protect oneself as well as the equipment.
a. What is electrostatic discharge (ESD), what problems does it cause and
how do you avoid it?
b. How can you avoid electrocution (i.e. how do you avoid getting an electric
shock), when working on a personal computer (PC)?
(5p)
a) A flow of current between two objects of dissimilar voltage potential, within
the context of computer systems administration this is often between some
computer component and the service technician 1p. The discharge can damage the
electronic component 1p. Discharge between technician and component can be
avoided by ensuring that both are at the same voltage potential, e.g. by sharing the
same ground (touching the chassis, ESD wrist strap, ESD mat) and by avoiding
the build-up of electrostatic charge. 1p
b) Ex: Always unplug equipment from high voltage sources (e.g. the wall socket)
when working on them. “One-hand” rule, avoid creating a closed circuit across
your chest. Be aware that some components may still hold a charge after being
disconnected (e.g. capacitors). Do not service high-voltage components such as
the power supply unit (PSU) 2p
4. What are the advantages of using diagnostic software rather than physical
inspection to identify the central processing unit (CPU) of a computer system?
1
Written Exam, 7th January 2009
Computer Systems Administration TE2003
(2p)
Ex: No need to remove heatsink/fan etc. Most software shows information about
cache size etc, no need to first find CPU id then look up the details. Possibility to
run benchmarking if supported by diagnostic software.
5. ATA, SCSI and PCI are all examples of data buses. What is a data bus and what
are its advantages when compared to point-to-point connections?
(2p)
A bus is a shared communication medium for a number of devices in contrast to
dedicated point-to-point connections between each device. The main advantage is
that a bus requires less connections, making it easier to add/remove devices from
the network/system, also the number of connections increases linearly with the
number of connected devices.
6. Troubleshooting is an important skill for computer administrators, and doing it in
a structured way is useful.
a. Give examples of three hardware problems and their symptoms.
b. Pick one of your symptoms from a) and draw a diagnostic flowchart with
at least four test cases for how to find the cause of the symptom. (Make
sure you use stepwise elimination, i.e. do not connect all test cases to the
root node of your diagram.)
c. Pick one of your problems from a) and perform a root-cause analysis
(RCA). Do at least five steps in your analysis choosing causes that you
think could be likely in a real scenario.
(6p)
a) 2p for three reasonable problem/symptom pairs. Ex: The system is completely
dead when pushing the on-button is a symptom of a blown PSU fuse.
b) 2p for a correct chart according to the instructions, see lecture 4, pp. 14 for
details.
c) 2p for a “Five why’s” RCA. Ex: blown PSU fuse, why?, voltage spike, why?,
not sufficient surge protection and a recent lightning strike, why? …
7. Assume you need to encode a picture consisting of 100 pixels (i.e. the image is
divided into a grid of 10x10 squares, each square having a specific color). The
number of colors used in the picture is 16. How many bytes do you need to
represent the picture digitally? Show your calculations.
(2p)
With four bits we can encode 2^4 = 16 colors. Four bits per pixel and a hundred
pixels, 4*100 = 400 bits. One byte is eight bits, i.e. we need 400/8 bytes = 50
bytes. 1p for correct number of bits/pixel, 1p for knowing there are 8 bits to a
byte.
8. Give three reasons for assigning user permissions (e.g. read/write access) to files
in an operating system.
(3p)
Ex: Protect against access by unauthorized users. Protect against accidental
deletion by authorized users. Protect against deletion/modification by software.
2
Written Exam, 7th January 2009
Computer Systems Administration TE2003
9. Hard drives frequently fail and this is a common reason for losing important data.
a. How can RAID be used to protect data in this case?
b. Backups are another way of protecting important data; give two examples
of methods (not media) for data backup.
(4p)
a) RAID uses more than one disk to increase performance and reliability. The
types of RAID we have talked about in the course that provide redundancy is
primarily RAID1 (mirroring) and RAID5 (striping+parity), RAID1 duplicates
data on several drives and can handle all drives failing but one, RAID5 stripes
data and uses parity to tolerate one disk failing. 2p
b) E.g. full backup, incremental backup, differential backup. 2p
10. At the university all computers in the labs are locked using a padlock, i.e. they
cannot be opened physically. From a security viewpoint and based on what you
have done in the exercises, give examples of why it is a bad idea to allow physical
access to the internals of a public computer.
(3p)
Ex: The BIOS password can be removed using motherboard jumpers, theft of
components, drives can be removed and data read without the right user
permissions, the boot-sequence can be changed to allow booting from e.g. a usbstick or CD.
11. Assume that you have built a PC but you have forgotten to put in any memory
modules (RAM modules). How will you most likely detect this when the system
is turned on and what is this phase of the boot sequence called?
(3p)
The computer, e.g. the ones used during the exercises, will emit a beep-code
indicating that there is a something wrong with the system memory. This will
occur when booting the PC during the POST-phase (Power-On Self Test)
12. Is it possible to use different types of file systems (for example EXT2 and NTFS)
on a single hard drive, and if it is, describe what steps must be taken in order to do
so?
(3p)
It is possible to use several filesystems on a single drive by first partitioning the
drive using partitioning software, and then formatting the partitions to use the
required file system
13. Compact discs (CD) can be of the write-once type and of the re-writable type.
Describe what the two types have in common as well as what is the difference
between them when it comes to how information is physically written and read
from them.
(3p)
3
Written Exam, 7th January 2009
Computer Systems Administration TE2003
In both cases a laser is used both to read and write data to the discs. On a writeonce CD the reflectivity of a layer of dye in the disc is changed permanently using
the laser. On a re-writable CD the laser is used to change the reflectivity of a
metallic layer which can then be changed back again.
14. Explain what Windows’ safe-mode is used for and why it is different from the
normal mode of Windows.
(3p)
The difference between normal and safe-mode is that in safe-mode only a limited,
functionally verified, set of drivers and system software is started on boot-up.
This allows the user to fix problems caused by software components loaded at
start-up. An example could be removing a newly-installed graphics driver that
crashes the computer when loaded, or as in the lab removing a program placed in
the startup folder that is freezing the system.
15. What is it important to turn off a computer using the operating system command
(or software controlled button)?
(3p)
Buffers must be flushed, hardware must be stopped in a controlled way (e.g. hard
drive heads need to be parked), data in volatile memory must be stored in
permanent storage.
4