What do these abbreviations stand for?

Question

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.

Pedantry, I know, but FYI /etc, /opt, /bin and the rest are *not* acronyms: http://en.wikipedia.org/wiki/Acronym — Zayne S Halsall, May 01 '10 at 09:04
@Zayne You're right. I edited the question. But I was sure that `etc` was an acronym. — Luc M, May 01 '10 at 13:47

iainlbc · Accepted Answer · 2010-08-04T05:39:12.120

42

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

edited Aug 04 '10 at 05:39

answered May 01 '10 at 01:56

iainlbc

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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 02 '10 at 02:25
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Also, here's a good breakdown of the directory structure on FreeBSD: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/dirstructure.html – iainlbc Apr 30 '12 at 16:39
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/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: http://bitsavers.trailing-edge.com/pdf/bellLabs/unix/PreliminaryUnixImplementationDocument_Jun72.pdf (p.13-14 in the PDF) from Bell Labs in ’72. – moeffju Apr 09 '14 at 12:29
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@moeffju - thanks the the 'bitsaver' I remember single-stepping though UNIX v7 code to learn the meaning of interrupts. And, yes - my first home directory was /usr/michael - and /usr/local was "born" to allow users to add stuff in a "local" root. My guess that /usr became "UNIX Software Repository" is because /usr/src is where you (re-)built UNIX whenever you added a device (or fixed a bug). My other favorite file was /usr/sys/conf.h - as that is the file I remember as being the conf file of conf files (e.g., where disk partitions were defined). Ah - the memories :) Great start of a new year! – Michael Felt Jan 10 '17 at 07:26
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@iainlbc I don't think so, I think its "User System Resources" if not just short for "user"... https://www.tldp.org/LDP/Linux-Filesystem-Hierarchy/html/usr.html – AndyPerlitch Feb 04 '19 at 18:41

score 29 · Answer 2 · answered May 01 '10 at 02:10

29

You might find the output from "man hier" fascinating

answered May 01 '10 at 02:10

Matt Simmons

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Nice. It's funny because `hier` means yesterday in french. Hierarchy wasn – Luc M May 01 '10 at 05:10
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@Luc_M and in German "hier" means "here." :-) – splattne May 01 '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 01 '10 at 20:38
If you don't have a linux system on hand just google *man hier* – AaronLS Sep 13 '12 at 02:47

score 7 · Answer 3 · answered May 01 '10 at 15:09

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 :)

Kyle Brandt · Answer 4 · 2010-05-01T02:00:12.483

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

edited May 01 '10 at 02:00

answered May 01 '10 at 01:48

Kyle Brandt

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+1 That likely would have answered this [now closed] question. http://serverfault.com/questions/137328/whats-the-most-widely-used-pronunciation-of-the-unix-etc-directory/137397 – jscott May 01 '10 at 12:46

score 1 · Answer 5 · answered Sep 13 '12 at 03:31

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".

What do these abbreviations stand for?

5 Answers5