The history of Unix systems and their main components.

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526
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2answers
120k views

Why was '~' chosen to represent the home directory?

I have often wondered why the ~ represents the home directory of a user. Is there a reason behind this, or is it just some infrequently used character?
126
votes
5answers
13k views

What's the story behind Super Cow Powers?

As we know, apt-get has Super Cow Powers and aptitude does not: $ apt-get --help | grep -i cow This APT has Super Cow Powers. $ aptitude --help | grep -i cow ...
94
votes
3answers
14k views

What does “rc” in .bashrc stand for?

Is it "resource configuration", by any chance?
93
votes
5answers
23k views

Is Linux a Unix?

So, there are lots of different versions of Unix out there: HP-UX, AIX, BSD, etc. Linux is considered a Unix clone rather than an implementation of Unix. Are all the "real" Unices actual descendants ...
84
votes
3answers
5k views

Why not use “which”? What to use then?

When looking for the path to an executable or checking what would happen would you enter a command name in a Unix shell, there's a plethora of different utilities (which, type, command, whence, where, ...
81
votes
6answers
25k views

Where did the “wheel” group get its name?

The wheel group on *nix computers typically refers to the group with some sort of root-like access. I've heard that on some *nixes it's the group of users with the right to run su, but on Linux that ...
73
votes
3answers
11k views

Why is the root directory denoted by a / sign?

I have done some research about this on Google, but the results were cloudy. Why is the / sign used to denote the root directory. Are there any solid reasons behind it?
73
votes
4answers
10k views

Why are tar archive formats switching to xz compression to replace bzip2 and what about gzip?

More and more tar archives use the xz format based on LZMA2 for compression instead of the traditional bzip2(bz2) compression. In fact kernel.org made a late "Good-bye bzip2" announcement, 27th Dec. ...
42
votes
4answers
4k views

Why does no one use the true Bourne shell as /bin/sh?

I've noticed that basically no system I've ever worked with has /bin/sh as a real executable. It's always a symlink to dash, bash in POSIX mode, or something similar. Why? What are the disadvantages ...
37
votes
2answers
7k views

Why is 'umount' not spelled 'unmount'?

I am wondering if there is any historical or practical reason why the umount command is not unmount.
37
votes
1answer
2k views

What happened to bzip1?

bzip2 had been a de facto standard for quite strong compression throughout many years already. I myself had typed the bzip2 command thousands of times already, which makes me wonder - what happened to ...
36
votes
5answers
4k views

Why is there a * When There is Mention of Unix Throughout the Internet?

I've noticed that throughout the Internet, within forums and blog posts, Unix always has a * in the word, whether it is *nix or Un*x, as I noticed at the welcoming banner at the Unix StackExchange ...
30
votes
5answers
811 views

How to save a command you entered without executing it? [duplicate]

Every Linux user has experienced this annoying thing: you begin typing a long and boring command, then realise you should have executed another one before. How to save the first one to execute it ...
28
votes
3answers
6k views

What did Ken Thompson mean when he said, “I'd spell create with an 'e'.”

Ken Thompson, the creator of Unix, was once asked what he'd do if he had it to do over again. He said, "I'd spell create with an 'e'." What is Ken referring to? Is there a "creat" command?
28
votes
3answers
6k views

What is the purpose of the hash command?

If you run hash it shows the path of all commands run since the hash was last reset (hash -r) [root@c04c ~]# hash hash: hash table empty [root@c04c ~]# whoami root [root@c04c ~]# hash hits ...
27
votes
5answers
5k views

Why do /usr and /tmp directories for Linux miss vowels in their spellings?

I have often started to think about this but never found a good answer. Why are these two Unix directories not /user and /temp instead? All the other directories under root seem to be exactly what ...
24
votes
4answers
2k views

What is GNU Info for?

I understand what GNU Info is and how to use it, but what is it for? Why does it exist in parallel to the man pages? Why not write detailed man pages rather than provide a separate utility?
24
votes
1answer
2k views

Were all Unix commands re-written in Linux?

I would like to know which commands were re-written for Linux and which were retained from Unix? I'm new to Linux.
24
votes
3answers
4k views

Why is dmesg called dmesg?

Is there any explanation/history behind the name of the command dmesg (which prints out some kernel messages)?
24
votes
1answer
3k views

Why was '.' chosen to represent the current directory and '..' for parent directory?

After reading this question Design question: Why was '~' chosen to represent the home directory?, next obvious question on my mind was why '.' and '..' was used to represent current directory ...
22
votes
5answers
2k views

What aspects of Plan 9 have made their way into Unix?

Plan 9 was developed by Bell Labs as a successor to Unix. Although for various reasons it never quite materialized as such, a fair amount of development still went into Plan 9. My question is, what ...
22
votes
4answers
4k views

Single dashes `-` for single-character options, but double dashes `--` for words?

Where did the convention of using single dashes for letters and doubles dashes for words come from and why is continued to be used? For example if I type in ls --help, you see: -a, --all ...
20
votes
1answer
1k views

What does Ritchie's 1979 PDP-11 `/usr/games/bcd` do?

I recently tried the simh emulator pdp11. The disk image I used can be found on the internet, and instructions for booting it are here. Presumably it belonged to Dennis Ritchie, as the username is ...
20
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2answers
1k views

Why do Unix man pages use double backticks in place of double quotes?

I've noticed that man pages and other documents formatted by Unix utilities often use double backticks `` followed by double single quotes '' to wrap quoted phrases instead of the double quote ...
20
votes
1answer
415 views

When and how was the double-dash (--) introduced as an end of options delimiter in Unix/Linux?

I don't think the shell/utilities in historical Unix nor in something as "recent" as 4.4BSD supported using a double-dash(or two consecutive hyphens) as an end of options delimiter. With FreeBSD, you ...
20
votes
3answers
8k views

Why does Unix time start at 1970-01-01

Why does Unix time start at 1970-01-01? Why not 1971-01-01 or any other date?
19
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1answer
720 views

At what point did the /home directory appear?

Originally in Unix, /usr was used for user (home) directories. So if I had a user named alex, my home directory would be /usr/alex. (Interestingly, Plan 9, the successor to Unix, still has user ...
18
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2answers
2k views

Origin of 'root' account

What's the origin of root account? Where did it come from and why is it called root anyway? (Originally asked by @lizztheblizz on Twitter.)
18
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1answer
945 views

If chown can change groups, why was chgrp created?

So there's chown which lets you change the owner and group of files and/or directories. But there's also chgrp which only changes the group. Why was chgrp created? Isn't it redundant?
18
votes
3answers
185 views

How did the Linux Kernel project track bugs in the Early Days?

We all know that Linus Torvalds created Git because of issues with Bitkeeper. What is not known (at least to me) is, how were issues/tickets/bugs tracked up until then? I tried but didn't get anything ...
18
votes
1answer
684 views

What shells were used on early unix systems?

According to wikipedia, the Bourne shell was introduced in 1977 and C shell in 1978, but unix itself dates back to 1969. If you were using a unix system before 1977, what shell would you have been ...
16
votes
2answers
1k views

What is Unix now?

As I read in Wikipedia, Unix started as a revolutionary operating system written mostly in C allowing it to be ported and used on different hardware. Descendants of Unix is mentioned next, mostly BSD. ...
16
votes
2answers
2k views

Why is JFS so obscure?

When I first got into using Slackware years ago I quickly learned to love JFS over ext3 or reiserfs given that it was reliable and if there was an unclean shutdown, its disk checking was very very ...
16
votes
2answers
3k views

What is a socket?

Could someone explain to me what a socket is? I see it in many acronyms in context of SSL, etc. Also, why is it called a socket? Is it purely because it was what a name they invented? Or was it the ...
16
votes
0answers
491 views

How did the system settings directory on UNIX come to be named /etc? [duplicate]

Possible Duplicate: What does etc stand for? And why isn't it named /cnf or /syscf or /cfg? No one I have ever asked has been able to tell me, not that I have access to any of the minds ...
15
votes
2answers
2k views

Who is responsible for the Linux kernel?

As of today, there are many Linux distributions like Ubuntu, Fedora, Gentoo, Mint, Debian, etc. These distributions update at different cycles. Ubuntu seems to update its kernel weekly or monthly, ...
15
votes
2answers
490 views

Use of ^ as a shell metacharacter

I wrote a small script today which contained grep -q ^local0 /etc/syslog.conf During review, a coworker suggested that ^local0 be quoted because ^ means "pipe" in the Bourne shell. Surprised by ...
14
votes
4answers
785 views

How was the shift to 64 bits handled on Linux

How was the transition to 64 bits handled on Linux/Unix? The Windows world still seems to have issues with it and I'm curious how it was handled in the *nix world.
14
votes
2answers
2k views

Origin of the word cron?

Trying to settle a friendly argument. Is "cron" an acronym for something? Additionally, did it's current canonical name "cron" originate from something shortened for something like chronos or ...
12
votes
4answers
1k views

How did they manage to drive a Unix computer before mice and copy & paste?

Since Unix is 40 years old, Unix is older than the invention of the computer mouse. (actually only 3 years if Unix is from 1969 and the mouse from 1972) How in the world did a new user do anything ...
12
votes
3answers
598 views

Why do we need the reboot function in different binaries?

Why do we need the reboot function in different binaries? shutdown -r and reboot Or do they differ in something?
12
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2answers
12k views

What is the concept behind “tty” in linux?

Where did the terminology "tty" come from in Linux?
12
votes
2answers
2k views

What are the main differences between BSD- and linux-based operating systems?

I am a long time linux user and have recently become interested in playing about with BSD-based operating systems. What are the differences between linux and BSD-based systems. I am interested in ...
11
votes
1answer
765 views

What do all the pictures on the front of the “Unix and Linux System Administration Handbook” represent? [duplicate]

I'm a newcomer to Unix and Linux, and I've been trying to get up to speed on everything. One of the guides I've used is the "Unix and Linux System Administration Handbook" It's a pretty great book, ...
11
votes
1answer
486 views

What is the difference between shared memory in early unix systems vs modern unix systems?

How could processes share memory in early versions of UNIX version modern implementations of shared memory?
10
votes
4answers
4k views

Evolution of Operating systems from Unix

Can you explain the evolution hierarchy of operating systems (Linux and Windows) from Unix?
10
votes
2answers
6k views

Is `cal` broken? What happened in September 1752?

If you look at the output of cal 9 1752 you will see this strange output: September 1752 S M Tu W Th F S 1 2 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 The following story ...
10
votes
4answers
519 views

The future of OpenSolaris

since OpenSolaris is more or less abandoned by Oracle, is there a nice alternative that implements the unique features of OSOL? ZFS is one thing, but I liked the image creation system, that let you ...
10
votes
2answers
473 views

/usr/bin/ptx: Can you provide a use case or two?

I was going through the list of files included in coreutils and I was able to come up with an example of how I could personally use all of the commands provided except for ptx. Can you give one or two ...
9
votes
3answers
3k views

What is the point of the 'operator' user?

Many un*x systems ship with a user account named 'operator'. What is the purpose of this account? Do some systems actually make use of this account, or is this more of a historical legacy? Have you ...