[nycbug-talk] Re: MSNBC on the decline of technology jobs

[Jed Davis]

In article <Pine.LNX.4.44.0506221203350.11177-100000 at bawx.pilosoft.com>,
 <alex at pilosoft.com> wrote:
> I have a list of questions I like to ask on interviews from prospective 
> employees, I should share it and you can see how well would you do.
> 
> Some of those questions are intentionally tricky. For some, nobody [with
> few rare exceptions] knows the answer offhand, and I really evaluate
> thought process how would someone try to solve it.
> 
> Network questions:
>
> * How many fields in an IP header router will change while forwarding?
> [ttl and crc]

Record-route options, anyone?

> * Why should you have recursive dns server separate from authoritative dns 
> server [cache growth/cache poisoning]

I was under the impression that modern nameservers resist cache
poisoning, and if the cache can grow beyond reasonable bounds, You
Have Other Problems.  As a general security principle, though, it
nonetheless makes sense to isolate <thing that random people can feed
malicious input to> from <source of important information>.  Especially
if individual hosts don't have their own local slaves, so a dead or
corrupted nameserver can devastate the entire network.

> Unix admin questions:
[]
> * What's an inode?

The physical representation of a potential file.  The name "inode" kind
of implies the traditional Unix filesystem or at least something similar
to it it; for example, while HFS file id's are a little like inode
numbers, and can be (and I think are) stuffed into st_ino, I don't know
that it's terribly meaningful to talk about inodes with HFS.

> What happens if you run out of inodes?

I'd find someone who speaks NetApp to go summon some more.  (-:

> How do you prevent yourself from running out? 

Estimate the average file size, divide volume size thereby, add margin
for error, and pray.

> * What's a sticky permissions bit?

Much like many aspects of Unix, it's something that makes more sense if
you're a PDP-11.

> * When would you use tar vs cpio? [silly question - but at least it would 
> show someone knows what cpio is]

1) cpio can be useful when you have a command like find(1) writing out a
list of files (in a nontrivial directory tree) you need to archive or to
copy somewhere.

2) Don't use either; use pax instead.  (-:

> * You are trying to unmount filesystem, but it tells you 'busy'. How would 
> you see what processes are using it? [fuser -m or lsof]

This gets more fun when the open isn't from a user process, but because
you swapctl -a'ed a file on the filesystem a while ago and forgot about
it.  (In my defense, that was a test system, and also I was doing this
at home.)

> * You screwed up boot block and server won't boot. You have the original 
> OS CD. How do you boot off the CD the OS on the current hard drive? [very 
> os-dependent, but in most cases boot -a will prompt you for root fs]

You don't, because you updated the system since the original install,
and the new userland isn't compatible with the old kernel on the CD, and
the bootloader isn't sufficiently powerful to nab the old kernel off the
hard drive. (-:


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