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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Interview Questions for a Unix Solaris System Admin
> -----Original Message-----
>
> you forgot to list the answers :)
>
> Waleed
>
Having been a past sys admin, it was difficult to resist the temptation to respond to the initial post. But, since at least one person appears to have taken it as an indication of what kind of sys admin a candidate will be, I could resist no longer. This kind of questioning is sort of like expecting an Oracle DBA to walk up to a box and type out a complete CREATE DATABASE command that is appropriate for whatever version of Oracle is installed on the box. It tests the ability to memorize trivia rather than what you might expect during normal daily operations. Knowing that most facts can be looked up, I would be much more interested in the person's general philosophy of how to manage things. Is the person a control oriented person or a service oriented person? Try to determine if the person tends to take the time to do things right, or if they tend to go for the quick and dirty solution.
Even though automation through scripting involves talent that most people do not have (just like most people are not talented musicians even if they learn a lot about music), I would still try to get some idea of how much talent the candidate has. Somebody who is a skilled script writer can, in effect, work 24 hours per day in surrogate form via cron.
In general, I would place much less emphasis on the ability to spout off academic facts and more emphasis on practical day to day technique. I think some probing of the candidate's knowledge of backup and recovery is appropriate -- which means you kind of have to learn some of that yourself.
I took the liberty of providing what I think are good answers to some of the questions.
> -----Original Message-----
>
>
> 1) What is an inode? Bonus: What important piece of file
> information is NOT stored in the inode?
Might be better to ask the pros and cons and having many inodes as opposed to few; circumstances when you would not want to go with the default number you get when you create a file system (never happened when I was a sys admin).
Answer: If this file system is to be used for storing an outrageous number of little files, you might consider increasing the number. In the old days when disks were expensive, and you knew that only a few big files were going on the file system, you might get a little more storage by cutting back on the inodes.
I think a more practical question would be to ask how to determine if two file names refer to the same file; that is, the names are hard links.
Answer: They have the same inode number as displayed by ls -i
You could ask for a discussion of soft links versus hard links. For
example:
- soft links can refer to something on another file system; hard links
can't.
- a file exists as long as it has at least one hard link; a soft link can
point to a non-existent file.
- you can rename a file by creating a hard link, then rm the original file
name; can't do that with soft links.
- a soft link is essentially a file; a hard link is not.
You might ask the circumstances under which the admin would AND has used soft links. In the past, I had the unpleasant experience of inheriting servers where the previous admin(s) had made extensive use of soft links resulting in boxes rife with spaghetti file systems. This usually happens because, for one reason or another, a bunch of files need to be moved from one place to another; then instead of fixing whatever uses those files to tell it to go the new location, a soft link to the new location gets created as a quick and dirty solution. These things accumulate, and eventually you have a mess and booby traps ready to blow up.
> 2) What is priority paging and how does it work? (mildly dated, but
> useful if they claim to have been around for a while)
Never heard of it. Sounds like a term for a type of swapping (lazy versus not lazy).
> 3) What does sr stand for in vmstat output?
man vmstat.
> vmstat
Virtual Memory Statistics: (pagesize = 8192)
procs memory pages intr cpur w u act free wire fault cow zero react pin pout in sy cs us sy id
Ummm ..... got no sr here ....
> 4) How would I configure the gigabit ethernet interface to force it to
> be full duplex?
I guess if this were a common daily activity, you would want somebody to know how to do this. For most places, you might do this ... ohhhh ... maybe once per year ... maybe.
> 5) How does RAID-5 work? Bonus question: how does raid-4 work?
> Extra-extra bonus question: how does raid-3 work?
Most people will know that it involves stripe with parity; but better, I think, to ask about pros and cons of RAID-5 versus 0+1 (or 1+0).
> 6) What's the difference between the passwd and the shadow files?
This is OK. I think I would phrase it as: What is the purpose of a shadow file.
Answer: It's where the encrypted password is (or can be) stored and is readable only by root. passwd file is world readable. If the encrypted password is visible, it makes it easier to run a cracker against it to try to discover poorly chosen passwords.
> 7) What's the difference between the dsk and rdsk devices in
> /dev? Bonus
> question: what's the difference between a block and a
> character device?
The high level answer involves "raw" versus "cooked" and how the OS accesses the device. With the complexities of OSes these days, I would be hesitant to try to discuss this stuff at the low level. Usually, if some activity requires using a raw device, then you are told that. As a sys admin, about the only time you work with raw devices directly, outside an application, is when you are working with disk partitions which, with the ascendancy of advanced filesystems these days, I wonder how much this is done now.
> 8) How do journaling filesystems work?
Usually, pretty well.
I think I would be more interested to know why one would use a JFS as opposed to UFS. I think the original reason for JFS was faster crash recovery (but how often does your system crash?). And one has to make some distinction between JFS and some brand of advanced filesystem. I think the terms tend to get smeared together sometimes.
> 9) What's the difference between ssh and telnet? Why is one
> preferable over the other?
No comment. I guess it depends on your organization and how likely it is that somebody is snooping the network.
> 10) What's the difference between the e4000 and the e4500
Answer: 500.
(Oh, do you mean that domain thing?)
I think both boxes are old models now.
> 11) What happens on an E6500 when I add boards in the bottom
> two slots?
Answer: You have to store your lunch somewhere else. Is fiddling with the guts of an E6500 with another one of those daily activities?
> 12) On an Sbus e-class I/O tray, what performance considerations do I
> have to keep in mind when I'm installing Sbus cards?
No comment.
> 13) Why is NIS bad?
Answer: It isn't. Depending on how your department operates, it might be very useful. If somebody wants to ypcat my encrypted password, go for it. You won't be able to crack it. I don't care what you do with Joe Stupid's password; that's Joe's problem.
> 14) What's the difference between TCP and UDP?
And the relevance of this to sys admin is what? Is your sys admin going to write a new network app and needs to decide what communication protocol to use? It your sys admin going to have a choice as to which protocol a daemon is going to use?
> 15) How does DNS work? Bonus question: is DNS TCP or UDP?
Usually, pretty well. Is your sys admin going to set up and manage a domain
and domain servers?
It might be useful to ask how to tell a box it's on a domain and get it
pointed at the domain servers. Or if a box is failing to resolve a name,
how to check if it's using a domain server and/or of the name is registered
with the server.
Now here's something else for you to test: The security considerations when Received on Wed Jul 16 2003 - 11:16:18 CDT
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