large directories

Message

tdennist · Post by **tdennist** » Tue May 18, 2004 12:05 am

What are the largest directories in a Gentoo system? I'm guessing /usr for one, but what are some other ones? I'm asking so I will know what's a good idea to give a separate partition to. If that makes any sense.

td

moocha · Post by **moocha** » Tue May 18, 2004 12:19 am

For a server, /var. For a desktop, /home.

tdennist · Post by **tdennist** » Tue May 18, 2004 12:20 am

And was I right about /usr? Also, this is a single user computer.

moocha · Post by **moocha** » Tue May 18, 2004 12:28 am

Yes, of course. Unless you're creating a lot of content (or downloading a whole lot of files

), /usr will take up the most space on any machine.
Note that some software (usually proprietary stuff, like non-open source games, Sun's JRE/JDK and a few others) install into /opt, not into /usr. So you might want to look at that.
At any rate, to see how much a directory takes up, run (from root) something like

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du -sh /home

Substitute /usr, /opt etc etc for /home to check those. Note that the command can take a little while to complete, especially when run on large trees, such as /usr.

tdennist · Post by **tdennist** » Tue May 18, 2004 12:30 am

Cool beans. What exactly is the /opt directory used for, anyway? And what does it stand for?

moocha · Post by **moocha** » Tue May 18, 2004 12:35 am

tdennist wrote:Cool beans. What exactly is the /opt directory used for, anyway? And what does it stand for?

Read my post again.
As for stand - it's short for "optional"...

tdennist · Post by **tdennist** » Tue May 18, 2004 12:37 am

Ah, "optional" kind of answers both of my questions :p

Thanks.

td

moocha · Post by **moocha** » Tue May 18, 2004 12:41 am

Not necessarily both of them - it's just a name, and it's that name for historical reasons, not for logical ones. Good example of UNIX tradition - "we've always done it that way"

Originally it stood for optional, but that doesn't mean it's for "optional software" - whatever that might mean. Aside from the kernel, pretty much any package is optional as there are always alternatives... And take a look at /usr. Comes from user, of course, but it doesn't have anything to do with user files, which land in /home. Or /etc, which holds system configuration. Not very intuitive.
Bottom line is - it's all about convention. If you want to know more about what goes where and why, see the File System Hierarchy Standard.

tdennist · Post by **tdennist** » Tue May 18, 2004 1:02 am

Oh. How unnecessarily confusing

.

I'll take a look at that link you posted.

td

floffe · Post by **floffe** » Tue May 18, 2004 9:10 am

moocha wrote:And take a look at /usr. Comes from user, of course

*BEEP* USR = Unix System Resources

Deebster · Post by **Deebster** » Tue May 18, 2004 11:13 am

tdennist wrote:I'm asking so I will know what's a good idea to give a separate partition to.

/tmp!
A short list of advantages/arguments:

Security - Having /tmp as a separate partition allows you to mount it with the options nodev,nosuid,noexec, which stops pretty much all linux attack scripts and worms (most use /tmp to exploit from&/build exploits). Be aware this could break things, although the only app I've ever heard of is Midnight Commander (apparently).
Portage was vulnerable to a trick with hard sym-links that you could do if your /tmp was on the same partition as /, although iirc that's fixed now.
Also, having /tmp and /var (/home too, depends) on separate partitions allows you to set / to read-only, although I only bother with that on servers.
Data integrity - /tmp is the area most written to, so keeping it on a seperate partition helps guard against corruption of the rest of your files.
If you fill up a separate /tmp partition, it doesn't break anything else (like logs and spools in /var). Trying to log on to a system with a full root partition or /var is no fun at all.
However, this is also an argument against having it separate - running out of space on /tmp is a pain, but so is having all that unused space (for most of the time, anyway). Not so much an issue if you've got a nice big drive and can afford a decent sized /tmp partition.
On a related note, the 'out of space on my xxx partition' problem is the reason why the Gentoo install guide suggests such a poor partitioning system (hi Sven!).
Allows you to mount /tmp using a different fs, like reiser4 or ext2 (fast, stability over crashes not needed) or even tmpfs (uses swap space, Solaris style).

moocha · Post by **moocha** » Tue May 18, 2004 12:21 pm

floffe wrote:
moocha wrote:And take a look at /usr. Comes from user, of course
*BEEP* USR = Unix System Resources

Argh

*goes and hides under a rock for the next couple of years*

lbrtuk · Post by **lbrtuk** » Tue May 18, 2004 2:36 pm

Deebster wrote:Having /tmp as a separate partition allows you to mount it with the options nodev,nosuid,noexec, which stops pretty much all linux attack scripts and worms

While at first, setting noexec might seem to be the perfect solution, but it can easily be circumvented. While the shell might not execute something that doesn't have the +x bit set, you can always easily run it though something that will run it.

ie- For a bash script, the cracker can do:

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/bin/sh /tmp/mynastyscript

For a python script (you get the idea):

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python /tmp/mynastyscript

For a binary executable:

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/lib/ld-linux.so.2 /tmp/mynastybinary

True that it adds another level of annoyance and that it might stop some scripted worms, but there's nothing to stop the cracker writing this into the worm script.

Deebster · Post by **Deebster** » Tue May 18, 2004 3:11 pm

Yup, which is why I wrote "pretty much all", not just "all"

Unne · Post by **Unne** » Wed May 19, 2004 3:06 am

*BEEP BEEP* http://www.google.com/search?q=usr+%22u ... 2+retronym

placeholder · Post by **placeholder** » Wed May 19, 2004 3:27 am

/ is a pretty big directory if you ask me. lol

floffe · Post by **floffe** » Wed May 19, 2004 4:24 pm

Unne wrote:*BEEP BEEP* http://www.google.com/search?q=usr+%22u ... 2+retronym

*goes and hides under a HUGE rock for the next couple of years*

moocha · Post by **moocha** » Wed May 19, 2004 4:27 pm

Hey, go find your own rock, this one's taken

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