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

alex at pilosoft.com alex
Wed Jun 22 14:27:28 EDT 2005

On Wed, 22 Jun 2005, Francisco Reyes wrote:

> Absolutely no clue. :-(
> > * Why should you have recursive dns server separate from authoritative
> > dns server [cache growth/cache poisoning]
> A guess. :-) Redundancy, growth and to prevent against malicious
> activities.
Yes. Recursive name server will listen to replies from other servers and
cache them. Potentially, they can be bad, affecting 'authoritative'
records. Authoritative name server won't listen to anything, it will just 
serve the data it knows are correct. 

> > Unix admin questions: * Solaris: how do you change fullduplexness of
> > an interface? [ndd /dev/xxx]
> Solaris.. what's that? :-) Not a Solaris person... (but I do know what
> it is .. at least) hehe.
Similar thing on linux - how do you do it? ifconfig gets half credit -
half the time it won't work through ifconfig, and you need to use ethtool.
Points to pointing out that ifconfig is deprecated. 

> > * What's an inode?
> Finally.. One, I think, I know. An Inode is how the operating system
> tracks files and their parts. It uses a B-Tree data structure to track
> files. Because of it's B-tree data structure it can quickly find a file
> or all it's parts.
Actually, inodes don't have much to do with btrees. The specific
implementation may (now you are getting into ufs vs ext2 vs jfs etc).  
Inode just has a list of physical blocks associated with this file.

Now, you may be also thinking about indirect inodes - but that's separate
thing and also filesystem-dependent. (look up
http://www.princeton.edu/~psg/unix/solaris/troubleshoot/diskio.html )

> >What happens if you run out of inodes?
> You can't create more files or expand files.
You can expand files, just not create new ones.

> >How do you prevent yourself from running out?
> If you are preparing a file system and you know you will have lots of
> files you can configure the parameters to newfs to have more inodes.
> If you already have the filesystem you may need to copy the files and
> re-do the filesystem. You could also use a mount point to move some of
> the files to a new partition.
Correct. Could get more points for noting that some filesystems don't use
static inodes and have infinite number available.
> You can also move all/some of the files to a different partition and use a 
> symbolink link in the original location.
> > * What's a sticky permissions bit?
> It's an additional permission beyond read, write, execute which can be set 
> on a file or a directory.
> >What if a directory is sticky?
> Only the owner of the file can edit the file.
Incorrect, anyone can edit the file (if file's permissions allow it), only
owner can delete it (note the difference between permissions on the *file* 
and permissions on the *directory*)
> > * When would you use tar vs cpio?
> Tar is more portable.
Eh, dunno about that actually. The question is whether you know what cpio 
is. :)

> > * You are trying to unmount filesystem, but it tells you 'busy'. How would
> > you see what processes are using it? [fuser -m or lsof]
> Don't know in Linux, but in FreeBSD lsof and fstat.
> >
> > * 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]
> Use the install CD to fix the boot block.
on linux, root=/dev/zzz, on bsd boot -a. Fixing i'd prefer an answer
that'd say 'grubinstall' or lilo or installboot

> > I can write down the questions I usually ask C/C++ people too, if
> > there's any interest.
> :-) Not a C/C++ developer..

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