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Some directories are easy to understand the meaning

/usr
/bin
...

But for the next ones, I have no idea.

/etc
/opt

opt for optional?
etc for electronic t...... configuration (no idea for t)

I would like to know what these abbreviations mean.

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Pedantry, I know, but FYI /etc, /opt, /bin and the rest are not acronyms: en.wikipedia.org/wiki/Acronym –  Zayne S Halsall May 1 '10 at 9:04
    
@Zayne You're right. I edited the question. But I was sure that etc was an acronym. –  Luc M May 1 '10 at 13:47
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5 Answers 5

up vote 27 down vote accepted

Strangely enough /usr actually means Unix System Resources.

"The "etc" in "/etc/bin" really does stand for "etcetera." In early Unix systems, the most important directory was the "bin" directory (short for "binaries" -- compiled programs), and "etc" was for trivial stuff like startup, shutdown and admin. The list of things you need for running Linux is: a program binary, etcetera, etcetera -- in other words, a sole vital item, plus some less important bits and pieces.

Today, "etc" holds system-wide configuration files that you'd almost never do without -- hardly unimportant." --http://searchenterpriselinux.techtarget.com/tip/0,289483,sid39_gci1098161,00.html

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I thought that /usr means users. But your explanation removes the strange feelings I had about my "translation". Thanks! –  Luc M May 2 '10 at 2:25
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Also, here's a good breakdown of the directory structure on FreeBSD: freebsd.org/doc/en_US.ISO8859-1/books/handbook/… –  iainlbc Apr 30 '12 at 16:39
    
/usr originally meant “user”. “Unix System Resources” is a backronym and it doesn’t make much sense either, because the system resources are in /bin and /sbin; /usr can be mounted much later from within a running unix system. Canonical source: bitsavers.trailing-edge.com/pdf/bellLabs/unix/… (p.13-14 in the PDF) from Bell Labs in ’72. –  moeffju Apr 9 at 12:29
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You might find the output from "man hier" fascinating

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Nice. It's funny because hier means yesterday in french. Hierarchy wasn<t my first thought :-) –  Luc M May 1 '10 at 5:10
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@Luc_M and in German "hier" means "here." :-) –  splattne May 1 '10 at 20:20
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The output doesn't answer the question (what do abbreviations like etc and opt stand for), but interesting nonetheless. –  Jonik May 1 '10 at 20:38
    
If you don't have a linux system on hand just google man hier –  AaronLS Sep 13 '12 at 2:47
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for the curious reader, sbin is short for “system binaries” (although it’s sometimes been described as being short for “static binaries”, because on some systems the executables in /sbin would always be statically-linked to ensure a bootable system if /lib was destroyed); lib, fairly obviously, stands for “libraries”.

/var contains “variable files” — things like logs, process IDs, temporary directories, mail spools.

/proc (on systems which have a proc filesystem) originally just contained information about running processes, but Linux extended this to include lots of other information, too (for example, cat /proc/cpuinfo).

On some older Unix variants, /etc often contained executable programs (and actually may still do, in some cases), rather than simply being restricted to configuration files. If memory serves, ifconfig was actually /etc/ifconfig on SVR4 systems some years ago.

If you use a Solaris machine, you’ll also see xpg4 (standing for “X/Open Portability Guide”), ccs (“C Compiler System”), and ucb (“University of California, Berkeley” — BSD compatibity).

You may find reading up on the FHS helpful :)

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/etc stands for et cetera. Wikipedia references a Bell Labs document from '72 that calls it etcetera.

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+1 That likely would have answered this [now closed] question. serverfault.com/questions/137328/… –  jscott May 1 '10 at 12:46
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The Filesystem Hierarchy Standard has information on etc history:

http://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard

There has been controversy over the meaning of the name itself. In early versions of the UNIX Implementation Document from Bell labs, /etc is referred to as the etcetera directory,[24] as this directory historically held everything that did not belong elsewhere (however, the FHS restricts /etc to static configuration files and may not contain binaries). Since the publication of early documentation, the directory name has been re-designated in various ways. Recent interpretations include backronyms such as "Editable Text Configuration" or "Extended Tool Chest".

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