41

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.

3

5 Answers 5

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

5
  • 3
    I thought that /usr means users. But your explanation removes the strange feelings I had about my "translation". Thanks!
    – Luc M
    May 2, 2010 at 2:25
  • 3
    Also, here's a good breakdown of the directory structure on FreeBSD: freebsd.org/doc/en_US.ISO8859-1/books/handbook/…
    – iainlbc
    Apr 30, 2012 at 16:39
  • 6
    /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, 2014 at 12:29
  • 2
    @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! Jan 10, 2017 at 7:26
  • 1
    @iainlbc I don't think so, I think its "User System Resources" if not just short for "user"... tldp.org/LDP/Linux-Filesystem-Hierarchy/html/usr.html Feb 4, 2019 at 18:41
29

You might find the output from "man hier" fascinating

4
  • 2
    Nice. It's funny because hier means yesterday in french. Hierarchy wasn<t my first thought :-)
    – Luc M
    May 1, 2010 at 5:10
  • 2
    @Luc_M and in German "hier" means "here." :-)
    – splattne
    May 1, 2010 at 20:20
  • 3
    The output doesn't answer the question (what do abbreviations like etc and opt stand for), but interesting nonetheless.
    – Jonik
    May 1, 2010 at 20:38
  • If you don't have a linux system on hand just google man hier
    – AaronLS
    Sep 13, 2012 at 2:47
7

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 :)

6

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

1
1

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".

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .