Not a Definitive List...

Linux has a history of including some fun "easter eggs" in its software. In this article, we'll tell you about some fun commands and options to lighten up your day. Not all of them are "easter eggs", but we think you'll enjoy them none-the-less.

Text Editors

Vim and Douglas Adams

Those of you familiar with Douglas Adams, writer of The Hitchhiker's Guide to the Galaxy, will appreciate a relevant help option included in the vim text editor.

If you haven't already, install vim. In Ubuntu/Debian, you can type:

sudo apt-get install vim

In CentOS/Fedora, you can type:

sudo yum install vim

Open the editor from the command line:

vim

Type the following to access a special vim help menu:

:help 42

What is the meaning of life, the universe and everything?  *42*
Douglas Adams, the only person who knew what this question really was about is
now dead, unfortunately.  So now you might wonder what the meaning of death
is...

Type the following, twice, to exit vim:

:q
:q

Emacs Games

Not to be outdone, Emacs, the text-editor famous for including everything but the kitchen sink, includes a surprising number of games that can be accessed from within the editor itself.

First, install emacs. On Ubunut/Debian, this would be:

sudo apt-get install emacs

On CentOS/Fedora, execute this command instead:

sudo yum install emacs

You can find out what games are available by checking out this directory:

cd /usr/share/emacs/*/lisp/play
ls

5x5.elc       decipher.elc    gametree.elc   meese.elc      spook.elc
animate.elc   dissociate.elc  gomoku.elc     morse.elc      studly.elc
blackbox.elc  doctor.elc      handwrite.elc  mpuz.elc       tetris.elc
bruce.el      dunnet.elc      hanoi.elc      pong.elc       yow.elc
bubbles.elc   fortune.elc     landmark.elc   snake.elc      zone.elc
cookie1.elc   gamegrid.elc    life.elc       solitaire.elc

To execute them, open Emacs:

emacs

Next, type theEsckey, followed byx(for execute), and then type the name of the game you wish to start:

Esc-x
pong

To quit Emacs when you are finished, typeCtrl, followed byx, and thenCtrlandc:

Ctrl-x
Ctrl-c

Apt Commands

Apt-get Cows

On Ubuntu and Debian, theapt-getpackage manager has had an embedded easter egg for a long time now.

If you type the help command for apt-get, you will get a hint:

apt-get help

. . .
. . .
  -c=? Read this configuration file
  -o=? Set an arbitrary configuration option, eg -o dir::cache=/tmp
See the apt-get(8), sources.list(5) and apt.conf(5) manual
pages for more information and options.
                       This APT has Super Cow Powers.

The last line tells us that the easter egg is active in this version of apt. Type:

apt-get moo

         (__) 
         (oo) 
   /------\/ 
  / |    ||   
 *  /\---/\ 
    ~~   ~~   
...."Have you mooed today?"...

Aptitude Cows?

With apt-get's affinity for cows, users may be curious as to whetheraptitude, another apt tool, also implements a fun easter egg.

We can check the help like before:

aptitude help

. . .
. . .
 -u             Download new package lists on startup.
                  (terminal interface only)
 -i             Perform an install run on startup.
                  (terminal interface only)

                  This aptitude does not have Super Cow Powers.

Well that is disappointing. Let's try it anyways though:

aptitude moo

There are no Easter Eggs in this program.

A fairly straight forward answer. But persistence is important. Let's add some verbosity:

aptitude -v moo

There really are no Easter Eggs in this program.

And again...:

aptitude -vv moo

Didn't I already tell you that there are no Easter Eggs in this program?

If you keep adding more "verbosity", you will eventually get this:

aptitude -vvvvv moo

All right, you win.

                               /----\
                       -------/      \
                      /               \
                     /                |
   -----------------/                  --------\
   ----------------------------------------------

It doesn't look like too much. Let's add another "v":

aptitude -vvvvvv moo

What is it?  It's an elephant being eaten by a snake, of course.

This is a reference to the book The Little Prince by Antoine de Saint-Exupéry.

Strange Options for Common Programs

There are some strange options available in some common programs that you may wish to check out.

Insult Users with Sudo

You can configuresudo, used to elevate the privileges of a command, to insult users when they type in an incorrect password.

To do so, edit the sudoers file with a tool called visudo, which edits and validates modifications to the sudo configuration file.

sudo visudo

Near the top, add a line that reads:

Defaults insults

Save and close the file.

Next, empty the cache that stores your password for a certain amount of time and then mistype your password for a sudo command:

sudo -k
sudo ls

[sudo] password for demo: # Type an incorrect password hereHave you considered trying to match wits with a rutabaga?
[sudo] password for demo: 
My pet ferret can type better than you!
[sudo] password for demo:
Wrong!  You cheating scum!

Script Kiddie Output for Nmap

Nmap is a commonly used network exploration tool that can be used to perform security audits on your system.

Install it on Ubuntu/Debian with the following command:

sudo apt-get install nmap

On CentOS/Fedora, install it by entering:

sudo yum install nmap

Nmap provides you with the unusual option of being able to output its data in "script kiddie" format.

Let's see what the normal output looks like first, by running the command against the Nmap website itself:

nmap scanme.nmap.org

Starting Nmap 5.21 ( http://nmap.org ) at 2013-09-18 17:43 UTC
Nmap scan report for scanme.nmap.org (74.207.244.221)
Host is up (0.072s latency).
Not shown: 998 closed ports
PORT   STATE SERVICE
22/tcp open  ssh
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 1.40 seconds

Now, let's enable the alternate output with these options:

nmap -oS - scanme.nmap.org

$tart|ng NMap 5.21 ( http://Nmap.org ) at 2013-09-18 17:45 UTC
Nmap $cAn r3p0rt F0r scanM3.nmaP.oRg (74.207.244.221)
Ho$t 1z Up (0.071z laT3ncy).
Not sh0wN: 998 cl0$Ed p0rt$
POrT   ST4TE $ERV!C3
22/tcp opEn  Ssh
80/tcP 0p3n  HtTp

Nmap d0n3: 1 iP AddrESz (1 h0$t Up) $canNed !n 1.34 secondz

Basically, it replaces certain letters with similar looking characters to emulate "hacker" language or leet-speak.

Command-line Star Wars

There are two different network-reachable, command line Star Wars tributes accessible from your terminal.

ASCII Art Star Wars Through Telnet

Simon Jansen, Sten Spans, and Mike Edwards created a full Star Wars tribute in ASCII (text) animated art accessible through telnet. In layman's terms: you can watch a text version of Star Wars in your terminal!

First, downloadtelnet, a precursor to SSH, if it is not already installed:

On Ubuntu/Debian:

sudo apt-get install telnet

On CentOS/Fedora:

sudo yum install telnet

All you have to do from here is point telnet to the correct server:

telnet towel.blinkenlights.nl

                                   /~\                               
         R2-D2!                   |oo )                              
     Where are you?         #     _\=/_    #                         
                             \\  /  _  \  //                         
                              \\//|/.\|\\//                          
                               \/  \_/  \/                           
                                  |\ /|                              
                                  \_ _/                              
                                  | | |                              
                                  | | |                              
                                  []|[]                              
                                  | | |                              
  _______________________________/_]_[_\_____________________________

When you've had enough, holdCtrland]. You will be given a prompt where you can type "close":

Ctrl-]
close

Star Wars Traceroute

A newer tribute to Star Wars has been achieved by Ryan Werber by naming the network hops to a specific address.

If you run traceroute, a program that traces the path of packets to a remote host, you will see the intro to Star Wars in the network names along the way.

Simply type:

traceroute -m 254 -q1 obiwan.scrye.net

The route will begin to populate. After a few stops, you will begin to see the magic:

. . .
. . .
15  Episode.IV (206.214.251.1)  77.506 ms
16  A.NEW.HOPE (206.214.251.6)  87.194 ms
17  It.is.a.period.of.civil.war (206.214.251.9)  77.699 ms
18  Rebel.spaceships (206.214.251.14)  78.171 ms
19  striking.from.a.hidden.base (206.214.251.17)  87.624 ms
20  have.won.their.first.victory (206.214.251.22)  86.249 ms
21  against.the.evil.Galactic.Empire (206.214.251.25)  77.505 ms
22  During.the.battle (206.214.251.30)  85.622 ms
23  Rebel.spies.managed (206.214.251.33)  78.121 ms
24  to.steal.secret.plans (206.214.251.38)  77.049 ms
. . .
. . .

After going through the introductions to Episodes IV, V, and VI, Ryan then continues with other avenues of entertainment:

99  Were.no.strangers.to.love (206.214.251.206)  77.472 ms
100  You.know.the.rules.and.so.do.I (206.214.251.209)  78.054 ms
101  A.full.commitments.what.Im.thinking.of (206.214.251.214)  78.512 ms
102  I.just.wanna.tell.you.how.Im.feeling (206.214.251.217)  79.884 ms
103  Gotta.make.you.understand (206.214.251.222)  79.427 ms
104  Never.gonna.give.you.up (206.214.251.225)  77.032 ms
105  Never.gonna.let.you.down (206.214.251.230)  78.909 ms
106  Never.gonna.run.around.and.desert.you (206.214.251.233)  80.286 ms

Installing More Fun

There are a few programs that you probably don't need for any other purpose, but can be fun if you have some time.

Learn from your Typos

If you've ever accidentally typed sl when you meant to list a directory's contents with ls, then you may want to install a program "sl".

On Ubuntu/Debian:

sudo apt-get install sl

On CentOS/Fedora:

sudo yum install sl

Now, whenever you accidentally type "sl" instead of "ls", you'll have to smile:

sl

                          (  ) (@@) ( )  (@)  ()    @@    O     @     O     @
                     (@@@)
                 (    )
              (@@@@)

            (   )
        ====        ________                ___________
    _D _|  |_______/        \__I_I_____===__|_________|
     |(_)---  |   H\________/ |   |        =|___ ___|      _________________
     /     |  |   H  |  |     |   |         ||_| |_||     _|                \___
    |      |  |   H  |__--------------------| [___] |   =|
    | ________|___H__/__|_____/[][]~\_______|       |   -|
    |/ |   |-----------I_____I [][] []  D   |=======|____|______________________
  __/ =| o |=-~~\  /~~\  /~~\  /~~\ ____Y___________|__|________________________
   |/-=|___|=O=====O=====O=====O   |_____/~\___/          |_D__D__D_|  |_D__D__D
    \_/      \__/  \__/  \__/  \__/      \_/               \_/   \_/    \_/   \

A train will chug across your screen each time.

Fun with Cowsay and Fortune

If you need some more cheap amusement at the command line, and didn't get your fill of cows from the "apt" easter egg, you can downloadcowsayandfortune.

On Ubuntu/Debian:

sudo apt-get install fortune cowsay

One CentOS/Fedora:

sudo yum install fortune cowsay

Cowsay inserts any input into a word bubble and draws an ASCII cow to talk to you:

cowsay "hello, I'm a cow"

 __________________
< hello, I'm a cow >
 ------------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

The fortune program spits out quotations, fortunes, jokes, nonsense that can be piped into cowsay:

fortune | cowsay

 ________________________________________
/ Q: What looks like a cat, flies like a \
| bat, brays like a donkey, and          |
|                                        |
\ plays like a monkey? A: Nothing.       /
 ----------------------------------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

If you're not too fond of cows, you can get other characters as well:

fortune | cowsay -f tux

 _____________________________________
/ You never know how many friends you \
| have until you rent a house on the  |
\ beach.                              /
 -------------------------------------
   \
    \
        .--.
       |o_o |
       |:_/ |
      //   \ \
     (|     | )
    /'\_   _/`\
    \___)=(___/

For a full list of the available characters, type:

cowsay -l

Cow files in /usr/share/cowsay/cows:
apt beavis.zen bong bud-frogs bunny calvin cheese cock cower daemon default
dragon dragon-and-cow duck elephant elephant-in-snake eyes flaming-sheep
ghostbusters gnu head-in hellokitty kiss kitty koala kosh luke-koala
mech-and-cow meow milk moofasa moose mutilated pony pony-smaller ren sheep
skeleton snowman sodomized-sheep stegosaurus stimpy suse three-eyes turkey
turtle tux unipony unipony-smaller vader vader-koala www

My personal favorite is the stegosaurus:

fortune | cowsay -f stegosaurus

 _________________________________________
/ Q: What lies on the bottom of the ocean \
\ and twitches? A: A nervous wreck.       /
 -----------------------------------------
\                             .       .
 \                           / `.   .' " 
  \                  .---.  <    > <    >  .---.
   \                 |    \  \ - ~ ~ - /  /    |
         _____          ..-~             ~-..-~
        |     |   \~~~\.'                    `./~~~/
       ---------   \__/                        \__/
      .'  O    \     /               /       \  " 
     (_____,    `._.'               |         }  \/~~~/
      `----.          /       }     |        /    \__/
            `-.      |       /      |       /      `. ,~~|
                ~-.__|      /_ - ~ ^|      /- _      `..-'   
                     |     /        |     /     ~-.     `-. _  _  _
                     |_____|        |_____|         ~ - . _ _ _ _ _>

As you can see, not very useful, but pretty fun.

Conclusion

This guide probably didn't impart any essential knowledge or improve your Linux abilities, but hopefully it helped you relax and perhaps even explore your system a little bit.

Let us know in the comments if you have any other good easter eggs or unusual, fun commands.