Hello! I have a simple question. What is /usr, and do I need it?What does it do? Thanks!

******Colonel Panic*******

What do yo mean do yo need it. It contains almost all of the software on your system. Please clarify!!!!

The directory /usr is one of the main branches of any linux filesystem tree.
As cinnix says it is the one that contains most your applications and system programs.
You could think of it as c:\windows for a windows system.

Well, I have heard that all you need is a swap, /boot, and a / (root) partition. This is why I was asking the question.

*****Colonel Panic*****

The /boot and / are all part of one big filesystem.
Windows separate different disks/partitions into several filesystems called c:, d:, etc.
Linux gathers all of your disks, partitions and even processes under global filesystem tree, called the root (/).
When you make a /boot partition for example you mount it to your /.
If you only use a /boot and a / partitoin then /usr is included in your /.

When people say the above the / encompasses all other directories that are not mounted from other partitions, if you get what I mean.

/usr typically contains a bulk of your binaries and it's typically pretty static, so it often suited to exporting over a network to all your workstation so they can run their programs from it, with /usr/local often then being mounted on a per-workstation basis so you can have different programs on different workstation. Hence the 'local' bit in the name. You don't see such a config much now though, but its part of the reason why lots of programs still default to /usr/local/ for their installation.

cheers

Jamie...

well, technically, the swap, / and /boot are all you need, and you're running linux, but the computer wouldn't do anything very interesting if that's all you have.

it might sit there with a blinking cursor... but that's about it.

Infact, I'd say that you really only need / as if you don't use LILO then you don't need /boot and swap space is just icing on the cake for when you run out of physical memory!!

Then again if you just want to run linux you can boot from a raw kernel boot disk and let it kernel panic about not being able to find any file systems. It's gotta be running to panic right?

Jamie...

Erm, sorry if this is a dumb question, but from the information that I am gathering from this, it seems like /usr is not a partition, but a directory. Or is a directory a partition, or what? Ya know, I just don't think I know what I am talking about. Please put me in line! Oh yeah, please don't get fustrated; you are talking to someone who is 100% newbie(my status even says so!). Thanks!

*****Colonel Panic*****

it could be either. if, during installation you made the /usr partition than it' s an actual partition with a predetermined size. if you didn't, then linux would create it in the / tree and its size depends on the amount of info in it at any given moment

Should I make a partition for /usr?

*****Colonel Panic*****

"Good programmers know what to write. Excellent programmers know what to rewrite"
--Eric S. Raymond

I don't know - do you want one?

But seriously folks. You don't 'need' other partitions for a simple workstation or desktop install. They can make your life more difficult than it needs to be. They can also make things better. Think of Linux partitions just like DOS/Win partitions. When you take a large hard disk and partition it with, say, three partitions, DOS/Win would tell you that they are three drives (as in Drive C:, D:, E. You would need to format them in order to be able to use them. In DOS lingo that would be 'format C:' with maybe some switches. Then you could install your Windows OS and keep your program data on the D: drive (your second partition) and maybe a backup on the E: drive (the third partition).

In *NIX/Linux these partitions are just different mount points on your file system. They can be mounted with options like ReadOnly, Append Only. You mount partitions on other disks for performance, or mount network exports (NFS).

(Damn. What was the question?)

I guess. I just want to get out on the right track. I'm just getting confused...

*****Colonel Panic*****

keep it simple - make it a directory. i can't think of any reason why /usr would be better off as a partition. the stuff that's contained in it isn't really specific enough to warrant it's own partition. i can understand if you want a separate partition for, say, your mp3 collection, but /usr doesn't make much sense to me.

what's the difference between partition and directory to /usr? or /boot...