Assignment

Partial credit will be given. Write down any assumptions you make if a question is not clear.

1. Job Ad:

On the internet, ?nd a job ad for a Unix Administrator and write down the URL. Sum up the most important quali?cations speci?ed in this job ad in 50 words or less.

2. Job Interview:

Assume you are interviewing for the job ad you found. The interviewer asks you what makes you quali?ed for the job. Explain three things you have learned about in this course that make you quali?ed.

3. Ethics:

You are a system administrator for a small company. One of the workers comes to you and says another employee is out sick, but a proposal that they have been working on must go out today. Therefore, he wants you to ?nd the ?le in the other employee's home directory and give him a copy, so he can ?nish the job.

(a) What reasons might you have for not ful?lling this request?
(b) What would make you feel ok about getting a copy of the ?le?

4. Boot up:

Explain how the booting process for your dual boot system is di?erent from that of your server with a single OS.

5. Shutdown:

Whenever something goes wrong with your friend's computer his solution is simply to reboot it. Explain why this is not usually the best solution.

6. No ping:

Assume you are trying to ping mainserver.cs645.UF from one of your client computers and it is not working. Give ?ve reasons why you might not get a response from my server.

7. Subdomains:

Assume that you want to de?ne a small network with 16 IP addresses beginning at 192.168.200.128. For this con?guration:

(a) What would the netmask be?
(b) What would the broadcast address be?
(c) What would be the likely address of the default gateway?

8. Changing my MAC: Assume your computer's network card is able to change its MAC address to anything it wants. Explain how DHCP and ARP might be compromised if this could happen.

9. Renew leases:

The DHCP protocol leaves it to the client to initiate the lease renewal process. Your friend wants the server to take over this job to cut down on network tra?c. In his scheme, the server will simply send out a renewal message at the time when the lease expires, if it wishes it to continue. If a client has not received such a message, it must assume it cannot continue and start acquiring a new lease from scratch. Point out any problems you see with this approach.

10. DNS resolution:

(a) Assume you want to send an email from one of your client computers to fred@quarry.bedrock.com. Explain how a query to ?nd the IP address for this computer is resolved by contacting various servers in the DNS system.

(b) Now assume you want to send an email from one of your client computers to fred@comp1.group9.cs645.FL. Explain how the resolution of this computer name di?ers from that in the ?rst part of this question.

11. More dynamic DNS:

You already know it is possible for the DHCP server to send requests to the DNS server to dynamically add A and PTR records for new clients. Your friend wants to add the ability to dynamically add NS records. Right now, if you create a new domain, you must contact the administrator for the server that will refer requests to you and get NS records added into its zone ?les manually. It should be possible to add these records automatically when your server gets started. Explain why this idea has not yet been implemented.

12. Wacky policy:

One of the reasons many sites make you change your password every 90 days is that was about how long it might take for someone to crack a password. Now that computers are faster, your fellow administrator thinks passwords should be changed once a week.

(a) Explain why you think this change in policy will cause more problems than it helps.
(b) What change in policy would you suggest that might work better to solve this problem?

13. Forgot my password:

The FL IT department is tired of dealing with students who have forgotten their passwords. They plan to install a card reader attached to an LCD display in Rawlings Hall. Whenever a student swipes their ID card, the password on their FL account will be reset to a randomly generated value and displayed on the LCD screen for the student to record for future use. Explain any problems you can see with this new approach to dealing with forgotten passwords.

14. Login trouble:

One of the users in your company is complaining that he can't login to his computer.

(a) Give a reason he might be having this trouble if the computer only has local accounts.
(b) Give two additional reasons why he might be having this trouble if the computer also has network accounts.

15. More login trouble:

(a) A user logged into his account on a client computer. He can see his ?les in his home directory, but he doesn't have permission to access them. Why?

(b) Another user logged into the same computer, but rather than seeing his ?les in his home directory, he sees those of someone else. Why?

16. Time fake:

Assume that the ntp server on your CentOS server somehow didn't manage to reset itself properly when Daylight Savings Time started, so the times it gave out to your computers were one hour o? from the rest of the world. Assume you discovered this the next morning and set things back to the way they should be. Explain an issue that might have occurred to anyone using the computers in your network before you ?xed the problem.

17. Sharing mail:

One way of sharing email, as opposed to systems like POP and IMAP, is to share the portion of the ?le system containing the mail ?les directly to all client machines. A local mail reader then simply looks at the contents of the ?le rather than fetching anything from a server.

(a) Describe one advantage of this approach.
(b) Describe one disadvantage of this approach.

18. NFS security:

The NFS protocol provides limited security features. Describe a security enhancement you think could be reasonably added to this protocol that would make things much better.

19. Super server:

You have been setting up your small networks so that all of the various services (DHCP, DNS, etc.) are installed on one server.

(a) Give two advantages to setting up your network this way.
(b) Give two disadvantages to setting up your network this way.