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What does the "etc" folder in the root directory stand for? I think knowing this will help me remember where certain files are located.

Update: Might be useful for others, the folder is used for "Host specific configuration files" - reference.

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A backronym I rather like is "Edit To Configure", but there is no history to suggest that this is a "real" meaning. –  dmckee Jun 11 '11 at 21:30
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My guess would be history. Nobody really thought "Hey, we're going to have a bunch of system-wide config data!" and so nobody ever created a directory for it. But, of course, there was, and everybody shoved it into /etc because there wasn't anyplace else to put it. Poof! De-facto standard. You know that /usr was originally the place where user home directories were? –  Omnifarious Nov 19 '12 at 22:32
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It's also (slightly) interesting to note that older versions of Solaris and HP-UX (and maybe others that I've forgotten) actually had binaries in /etc too. –  James O'Gorman Nov 19 '12 at 22:45
    
Until quite recently, *BSDs still put user home directories in /usr/home, in fact. –  michel-slm Nov 23 '12 at 7:33

7 Answers 7

up vote 32 down vote accepted

Define - /etc? has some good history.

You can find references to "et cetera" in old Bell Labs UNIX manuals and so on – nowadays it's used only for system configuration, but it used to be where all the stuff that didn't fit into other directories went.

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It could also now be used as a backronym for Environment & Tool Configuration. Which is descriptive of what it has become IMHO. This does not refute the historic origin though! –  Danny Staple Jan 11 '11 at 9:53
    
I like it Danny! –  Rafiq Maniar Jan 11 '11 at 10:00
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"et configurationa"? –  dotjoe Jan 11 '11 at 15:04

Originally, there was /bin for programs (essentially, executable binaries), and very soon /dev for device files and /lib for extra executable code loaded by programs (libraries). /usr also came in very early, first for user data, then as an extra OS area with its own bin and lib and then man containing the manual in electronic form. The source code was also often provided somewhere under /usr.

And there were a few files in the operating system that didn't fit in any of the existing categories. This included a passwd file containing users' passwords, and an mtab file written by mount, and the init and later rc programs executed at boot time, and over time more and more programs that were intended to be executed only for administration purpose and not as part of normal usage.

(You can browse some old Unix source code on the Unix Tree. Versions earlier than V6 are very fragmentary. You can also see V1 and V6 manuals at the Manual Page Library.)

At first, there was no connotation that files in /etc were configuration files. In these very early days, if you wanted to customize something, you'd be recompiling that part of the system. As Unix got more powerful, there were more and more things you could do without recompiling. As Unix got used more widely, there were more and more things people wanted to do, and they found ways of doing them without going through the trouble of recompiling. So /etc filled up with more and more text files that people could and did customize, hence it gradually became the configuration directory.

With the creation of /sbin to contain programs intended only for the system administrator, /etc ended up containing only text files, many of which can be customized by the system administrator. A few files (e.g. /etc/mtab, sometimes /etc/resolv.conf) are automatically maintained by system programs; there is a slow trend to move these files to /run in the Linux world.

On modern unix systems, almost all system-wide configuration files are under /etc, but not all files in /etc are configuration files. Typical Linux distributions and other unix variants don't cope very well with modifying many of the files that come from packages; at a minimum, you may end up having to merge local modifications manually when the system is upgraded.

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The file modification problem is being slowly solved by having programs read multiple configuration files from a directory. Some of those will be shipped with the package, and others supplied by users. The ones that are shipped may possibly be removed, but should not be user modified. Fantastic and informative answer BTW. –  Omnifarious Nov 21 '12 at 22:10

It means "et cetera". In Latin literally "and the rest". And I have proof.

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For those who don't know who Peter Salus is: amazon.com/Quarter-Century-UNIX-Peter-Salus/dp/0201547775 –  Warren Young Jan 12 '11 at 17:02

Wikipedia's Filesystem Hierarchy Standard Article offers an explanation on this.

Host-specific system-wide configuration files 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, 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".

Source: http://en.wikipedia.org/wiki//etc#Directory_structure

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I always assumed it was to suggest a miscellaneous directory, like "etc = all the rest we do not bother to categorize further"; I personally use such a folder too on my home directory as well (not called etc but "oars" = "(something) else").

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At the beginning of UNIX it was both necessary and practical to give short names to stuff. So, all system directories were kept to 3 letters and they are abbreviations. These names are still present on modern Linux systems. (ie. usr-user, var-variable, lib-library). etc comes from 'et cetera' but I've seen on several sites that a backronym is mentioned which would represent etc's present function: "editable text configuration", but again, this is just a modern adaptation to better represent what's in there.

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I thought it just meant "et cetera" as in "etc..." on a list.

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I've thought that as well, but it doesn't make sense to me. Why would a standard, root linux folder be named et cetera? But maybe that is the case... –  box9 Jan 11 '11 at 5:05
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Only the most impoverished category systems lack a "miscellaneous" category. Unix is plenty big enough to need a "misc" folder; they just chose a different name is all. –  Warren Young Jan 12 '11 at 17:03

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