CSCI 251 S06 Final Examination ============================== Instructions: - this is a closed book, closed notes, no electronic computing device exam - you have 3 hours to complete the exam - write all answers in the exam book provided - attempt all questions - state any assumptions - the exam consists of 8 (eight) questions - point values are given in square brackets; answer accordingly - maximum is 100 points - all questions pertain to material covered in lecture and lab - return this examination sheet with your booklet(s) Q1: [10] You just got the latest and greatest new release of the popular application 'A' on a CD. You insert the CD and start the program. It turns out that your three-year old computer is responding painfully slowly during loading as well as while running. In order to improve the performance, what are the areas you would look into and why? Q2: [12] Two friends decide to install the same version of a Linux distribution on their (somewhat older) PCs. While the installations go more or less smoothly, after installation is complete one reports that he cannot start X windows while the other complains that he cannot access the network. List three possible causes for each of the above problems and explain how you would go about proving or disproving each cause. Q3: [18] A small company, which connects to the Internet using the WAN IP address 142.25.203.17, has been allocated the IP subnet 192.148.48.0/28 for its internal use. The company wants to create two smaller subnets to be used by the two main departments. The two subnets are connected to each other and to the Internet using a router which has three network interfaces. Hosts in each subnet are able to communicate with each other and have access to the Internet. a. Give the network address, subnet mask and the range of IP addresses for each subnet. b. Draw a diagram showing how the networks are connected to the router to assure the desired connectivity. c. Assign suitable IP addresses to each of the router interfaces. d. Show the routing table (giving destination address, gateway, netmask and interface) of the router. (Assume that the packets bound for the Internet are sent by the router to the IP address 142.25.203.254 of the ISP.) Q4: [14] You install Linux on your PC using one of those distributions where, by default, the whole hard disk is divided into two partitions: the swap partition and one big root partition. After using the machine for a while, you notice that the (relatively small) disk is slowly getting filled up with your files. You decide to install an additional hard disk and move the users' home directories to the new disk. List the steps that you would take to achieve this, giving reasons why each step is necessary. Be as specific as possible and also state any assumptions. When the machine is rebooted after the disk installation is complete, the users should not notice of any other change than that they now have more space for their files. Q5: [14] Explain briefly the client/server paradigm used by most of the applications on the Internet. What are the 'protocol ports' and why have they been introduced? What are the so called 'ephemeral port numbers'? A command similar to 'netstat -ap' that you ran on Debian systems in the lab is run on a system. Some lines of the output along with the header is reproduced below (line numbers to the left have been inserted by hand). Proto Local Address Foreign Address State PID/Program name 1. tcp *:time *:* LISTEN 601/inetd 2. tcp *:discard *:* LISTEN 601/inetd 3. tcp *:daytime *:* LISTEN 601/inetd 4. tcp *:x11 *:* LISTEN 1338/X 5. tcp *:www *:* LISTEN 1314/apache2 6. tcp *:ssh *:* LISTEN 637/sshd 7. tcp *:smtp *:* LISTEN 591/exim4 8. tcp 192.168.18.1:1066 csciun1.mala.bc.ca:ssh ESTABLISHED 3067/ssh 9. tcp 192.168.18.1:2070 192.168.18.251:ssh ESTABLISHED 27873/ssh 10. tcp 192.168.18.1:www csciun1.mala.bc.ca:3834 ESTABLISHED 18584/apache2 Explain the meaning of these lines making reference to line numbers. Q6: [10] Some operating systems, including some early versions of Linux, come with a host of services readily configured for use. That is, everything is, by default, 'turned on'. Some vendors take the opposite approach that if you want a particular service, you have to specifically configure and enable it. That is, by default, everything is 'turned off'. What are the advantages and disadvantages of each approach? As a system administrator concerned about security, which approach would you find better? Why? Q7: [10] Suppose you find the latest version of some software on the developer's web site and you want to install it. While attempting to compile the program, the compilation fails with a number of error messages. You notice that some library is missing so you install that library first and recompile. This time you suceed. However, when you run the newly compiled program, it again fails with some error message saying something is not found. Explain the features of Debian package management system that allows easy installation and configuration of new software avoiding problems such as the ones encountered above. Q8: [12] After spending several days and hundreds of dollars cleaning up the mess created by the latest Windows virus, a small company (finally!) realizes the need of making regular backups of their data. They are able to allocate money to purchase either a CD/DVD burner or a tape drive for this purpose. As the RW (read/write) disks are known to be less reliable, if they decide to buy a CD/DVD burner, they would be using CD-R (or DVD-R) disks. Briefly outline the criteria the company should consider when making their decision and how these criteria would impact the decision.