I'm confused about some of the basic root directories. I'm posting what I think they do, please correct me where I am wrong. (Using slack10)

/etc

Some config files are found here

/usr

I think this is where you install user wide programs. For example, I compile programs into /usr/local/src/app and then install to /usr/local/bin /usr/local/lib etc...

/var

What is this directories purpose?

/opt

What is this directories purpose? It only KDE uses this dir.

/sys

This is empty, does/did it have some purpose?

/tmp

I'm assuming it's a temperary dir, that it's contents eventually get deleted, but I don't know how it works.

1) What's sticky for? I doReading man chmod, I think this is so everyone can write to /tmp, but can't overwrite/delete other user's files?

2) Does the /tmp dir get cleaned up itself, or should I write a script to delete it every once in a while?

3) Do you ever use the /tmp dir? For example if I did "$ find / -name foo 2>/dev/null 1>results", would you perhaps save the results on /tmp because it will get erased automatically?

thanks

re sticky bits: http://www.hackinglinuxexposed.com/a.../20030424.html

and re filesystem use:
http://tldp.org/HOWTO/HighQuality-Apps-HOWTO/fhs.html

1) You got the purpose of the sticky bit exactly right (it's called the sticky bit because in the days of yore, it was used on commonly-accessed executables to keep their text segments in memory, making them "sticky". When Unix got proper demand paging of memory back in the '70s, this was no longer needed, so the bit was re-used to provide an extra level of acces permissions to directories).

2) Depends on the distro -- some have scripts that clean up /tmp on reboot, and some don't. Writing a script to clean out files from /tmp that haven't been accessed in 3 days or more is a good newbie shell scripting project.

3) Yes, I use /tmp quite a bit. Mozilla and Firefox also download stuff to /tmp (like when you open a PDF from a Web page, the PDF is actually saved in /tmp).

I use /tmp frequently when I know I am going to create a mess of files that I will never miss. Basically, if I am testing a script... I will usually testbed it in a directory I make in /tmp (this is techically rude on multi-user systems as filling up /tmp with your junk might cause it to become full if it is on a seperate partition... but this is my personal computer so bah). I do that because I do have a cron script which removes all files which haven't been touched in three days. So, I can safely forget about it after I am done.

It is like being a kid again. I never have to clean up after myself... I just leave my toys laying about and my mother (the OS) cleans them up for me.

Oh, and

/opt usually holds optional software packages. Which stuff ends up here and not elsewhere is distro dependant.

/sys should be a link into the kernel sources. If it is empty then you might not have installed the source.

The /var directory is traditionally for things that change size dynamically. For example print spool files, mysql db files, apache, lock files and log files, etc etc ad nauseum :-)

Thanks for all the help!

1) The only part I was confused on was:I haven't compiled a new kernel yet, so maybe it changes, but for me /usr/src/linux is a symbolic link to /usr/src/linux-2.4.26/ which is my kernel source. /sys is a regular directory. (That's empty)

2) When writing a shell script to remove files older than X days, what should I do to special files? I noticed at least a socket, and a symbolic link files. Would I just "rm /tmp/oldFile" regardless if they are normal files? Or should I test for that and only remove files/dirs that are normal?

You probably ought to test for it. I notice things like MySQL sockets don't get their atime updated.