What do these abbreviations stand for?

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.

Solution 1:

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

Solution 2:

You might find the output from "man hier" fascinating

Solution 3:

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 :)

Solution 4:

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

Solution 5:

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".