Revision as of 09:30, 24 February 2008

UGCS Sysadmin Survey

What's involved in being a sysadmin?

Being a sysadmin means a lot of things. It means answering multitudes of questions from users. It means finding and installing nifty new software, and keeping the existing software working. It means keeping the lab's hardware working reasonably well as well as keeping the lab nice and neat. It means dealing with obscure problems that you might otherwise just ignore. It means being on call 24 hours a day to deal with minor and major emergencies. In general, it means spending a lot of time keeping the lab a productive and fun place to get things done.

What's the incentive?

As a sysadmin, you will learn the gory details of UNIX systems inside and out, and you will gain a lot of experience in dealing with machines and people which may be helpful in later life. If you're the type of person we're looking for, noodling around on computers will be its own reward. You'll become a well-known person among the undergrad community and the CS department. And you'll also experience the personal satisfaction of making UGCS a better place in which to compute.

How much time?

There are no fixed hours. When the lab crashes, we have to fix it, but otherwise we set our own schedule. You can work when you have the time, and let other people handle things when you don't.

Students have run this lab for over fifteen years while holding regular class schedules. It can be stressful at times (like midterms), but it's quite manageable. It is possible to keep this job over the summer while also working at something else at or very near Tech (like a SURF), but you have to be willing to spend a reasonable amount of time here. Generally, though, more important than the actual number of hours that you spend is your dedication to the job.

The dotted line

If the above hasn't scared you away from wanting to be a sysadmin, please answer the following questions and email your answers to sysadmin@ugcs.caltech.edu by Sunday, March 30 at 11:59pm (this is the end of spring break)

We will send you e-mail acknowledging receipt of your application. We will decide which candidates to interview and let you know by Sunday, April 6.

There have traditionally been between two and four sysadmins at any time. We would like to increase that number to have four sysadmins and several junior sysadmins. This opening is for junior sysadmins- however, we expect that given time (approximately a year, maybe a little less) all junior sysadmins will become full sysadmins if they would like to.

Since we are looking for people who will be able to remain sysadmins, we prefer sophomores and (especially) freshmen, but encourage everyone interested to apply. Previous experience in system administration is helpful but not at all necessary; more important is a desire to learn and the ability to deal with people.

In case of emergency... break glass...

Oh, and if you have any questions, contact one of us below. Although some of us seem surlier than others, we're all fine sysadmins.

Let the games begin!

1. Name:
2. Email address:
3. Class (Fr, So, Jr, Sr, S^n Sr):
4. Option (you don't have to be CS!):
5. What computing hardware, operating systems and software have you worked with, and what have you used them for?
6. What programming languages/scripting languages do you know? How well? Of the ones you know, which do you like best and least?
7. Describe one or two of your favorite programming projects (done for a class, for a job, on your own -- it doesn't matter).
8. What do you find to be the most interesting aspects of computing? When you "play around" with computers, what sort of things do you do?
9. Have you had any experience with system administration? What sort of work did you do (was it mangling an enterprise-wide gigabit-capacity network for a Fortune 500 company, or was it dusting off Apple II monitors in high school)? Have you done anything particularly interesting?
10. Have you worked with Unix-like systems at all? Have you ever set one up? (Yes, Linux counts.)
11. What is your biggest gripe about Unix? What would you change?
12. Emacs or vi?
13. What's the most difficult computer-related problem you've solved?
14. Why do you want to be a UGCS system administrator?
15. Is there anything else we should know? Be creative. Lie, if necessary.

Answer as many of the following questions as you can. Give as much detail as you can. You can ask people for help on any particular concept, but you can't have people answer the questions for you. Feel free to look at any documentation or source that you want. Don't worry if you don't know or can't figure out the answers - we're much more interested in your thought process than anything else. But remember: the more challenging problems you answer, the more chance you have to impress us. Please remember to cite your sources! Geez, sounds like a final, eh?

General UNIX

1. What is NFS? What problems does it have? How can these problems be solved?
2. What issues do you run into with a read-only root file system? How can you solve them?
3. What is a VLAN? What advantages does it provide?

Resource Usage

1. Suppose the mail server at UGCS has a load average of 100. Is this ok? Why or why not?
2. Suppose the web server on UGCS is locking up every 10 minutes. What could be going wrong? How would you fix it? Could you do it remotely?
3. Suppose a user process on a client machine is using a large amount of processor time and memory. Is this ok? (Hint: the answer is "it depends". Please elaborate on this answer)

Kerberos/AFS

A helpful resource might be the OpenAFS user's guide and the OpenAFS administrator's guide

1. If you try to set up your desktop for passwordless SSH to our login round-robin to.ugcs.caltech.edu, you have to enable the "GSSAPITrustDns" option. What is this option? Why do you have to enable it? Is there a way around it?
2. What does AFS use for most file access checks? Give some advantages and disadvantages of AFS's ACL scheme.
3. Does Kerberos have something like SSH keys? If it doesn't, what would it take to give Kerberos something like them? Is this desirable?
4. What does it mean when an AFS server says something like "Quorum does not exist" when you try to do a file operation?

Hypothetical questions

Troubleshooting

One of the biggest issues that the UGCS sysadmins face is dealing with machines when they stop working. Let's say you ssh to "to.ugcs.caltech.edu" and it hangs. What might be wrong?

Later on, you ssh to "to.ugcs.caltech.edu" and it keeps rejecting your password. What could be wrong?

For each scenario, list some possible issues and how you would distinguish between them.

Security

1. Our login machines are set up with a read-only root over NFS. Let's say a hacker obtained root on a login machine. What damage could they do? Could they do more damage if other people were logged on to the machine?

1. If you were a cracker or a miscreant trying to make the lives of the UGCS sysadmins utterly miserable, what sorts of things could you do? In a similar vein, what are some of the biggest security vulnerabilities in a Unix-like system? Suggest ways (policies, background processes, etc.) to circumvent these security problems.