Introduction to Linux Workshop and History: A Brief Overview

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February 15, 2016

George Garrett

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The HPC Support Team

Research Computing Services

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Linux Basics

(Scripting is next week)

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Session: Slides + Hands-on

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Please Leave Feedback

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What is Linux?

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What is Linux?

Linux is an operating system.

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What is Linux?

Linux is an operating system.

What is an operating system?

An 

operating system

 (

OS

) is software

that manages computer hardware and

software resources and provides

common services for computer

programs.

- Wikipedia

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This will be quick

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Linux is related to Unix

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1969 – Unix development starts

(complex history skipped)

1991 – Linux released

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- Dilbert, June 24 1995

(Idea stolen from Dan Mechanic at the Business School.)

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Ken Thompson & Dennis Ritchie

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Unix created by developers for developers

Unix was designed to be simple and powerful

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“ […] the power of a system comes more from the

relationships among programs than from the

programs themselves. Many UNIX programs do

quite trivial things in isolation, but, combined with

other programs, become general and useful tools.”

The UNIX Programming Environment

, Kernighan and Pike (1984)

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System: cunix.columbia.edu

User: Your UNI

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Windows Instructions

1.

Search for putty on Columbia home page

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Select first result

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Follow link to Putty download page

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Download putty.exe

5.

Run putty.exe

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Mac Instructions

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Run terminal

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$ ssh <UNI>@cunix.columbia.edu

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Host Name: cunix.columbia.edu

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Does everyone have access?

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-bash-4.1$

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This is the default prompt for our accounts

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Let’s make it a little more user-friendly

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-bash-4.1$ PS1="\W$ "

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PS1 is an environment variable

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\W is current directory

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$ is a conventional prompt symbol

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~$

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Name of current directory

~ is special

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These two files can be used to set up your

environment automatically when you log in

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Beyond the scope of this session

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$ pwd

“Print working directory”

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$ pwd

/u/1/a/abc123

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$ ls

“List directory”

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$ cd /

“Change directory”

$ pwd

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$ ls

$ ls –l

Long listing.

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$ cd

$ pwd

cd with no arguments takes you back home

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$ pwd

$ cd ..

$ pwd

“..” means “the directory above this one”

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$ pwd

$ cd .

$ pwd

“.” means “this directory”

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$ cd

$ ls -a

Can combine options

$ ls –la

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$ pwd

$ cd ~

$ pwd

“~” means “home directory”

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$ cd tmp

$ cd /tmp

Absolute: starts with “/”

Relative: doesn’t

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$ cd

$ cp /tmp/keets .

$ ls

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$ cp keets junk

$ ls

$ rm junk

$ ls

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$ cat keets

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$ mv keets keats

$ ls

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$ mkdir tmp

$ mv keats tmp

$ cd tmp

$ ls

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$ pwd

$ mv keats ..

$ cd ..

$ rmdir tmp

$ ls

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$ whoami

$ who am i

$ id

$ groups

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$ id abc123

$ groups abc123

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$ who

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$ w

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bash is a “shell”

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It prints the prompt and interprets what

you enter

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It has many keyboard shortcuts that can

really speed up your work

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$ ls jeats

ls: jeats: No such file or directory

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Up arrow to retrieve the command

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Left and right arrows to navigate on line

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Change the “j” to a “k” and rerun

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“^” means “hold down control”

^a : go to beginning of line

^e : go to end of line

^k: delete to end of line

Many more useful bash commands

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$ ls k[tab]

$ ls keats

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Tab completion

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Works for commands as well

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$ man ls

Display manual for “ls” command

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$ ls –l

total 4

-rw------- 1 user1  group 573 Sep 29 22:00 keats

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File type and permissions

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Link count

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User

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Group

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Date last changed

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File name

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$ ls –l

total 4

-rw------- 1 user1  group 573 Sep 29 22:00 keats

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$ ls –l

total 4

-rw------- 1 user1  group 573 Sep 29 22:00 keats

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$ ls –l

total 4

-rw------- 1 user1  group 573 Sep 29 22:00 keats

We’ll ignore links today.

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$ ls –l

total 4

-rw------- 1 user1  group 573 Sep 29 22:00 keats

The user that owns this file.

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$ ls –l

total 4

-rw------- 1 user1  group   573 Sep 29 22:00 keats

The group that owns this file.

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$ ls –l

total 4

-rw------- 1 user1  group   573 Sep 29 22:00 keats

The size of this file.

Here listed in bytes.

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$ ls –l

total 4

-rw------- 1 user1  group   573 Sep 29 22:00 keats

The last time the file was changed.

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$ ls –l

total 4

-rw------- 1 user1  group   573 Sep 29 22:00 keats

The file name.

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$ ls -l /bin/bash

-rwxr-xr-x 1 root wheel 768952 Sep 25 15:31 /bin/bash

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$ ls -l /bin/bash

-rwxr-xr-x 1 root wheel 768952 Sep 25 15:31 /bin/bash

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$ ls -l /bin/bash

-rwxr-xr-x 1 root wheel 768952 Sep 25 15:31 /bin/bash

Nine permission settings

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$ ls -l /bin/bash

-rwxr-xr-x 1 root wheel 768952 Sep 25 15:31 /bin/bash

Three groups of three

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$ ls -l /bin/bash

-rwxr-xr-x 1 root wheel 768952 Sep 25 15:31 /bin/bash

First group: owner

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$ ls -l /bin/bash

-rwxr-xr-x 1 root wheel 768952 Sep 25 15:31 /bin/bash

Second group: group

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$ ls -l /bin/bash

-rwxr-xr-x 1 root wheel 768952 Sep 25 15:31 /bin/bash

Third group: everyone else

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What’s the dot?

$ ls -l /bin/bash

-rwxr-xr-x. 1 root wheel 768952 Sep 25 15:31 /bin/bash

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Additional permission layer

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$ date

Tue Sep 30 13:27:29 EDT 2014

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$ cd

$ date > thedate

$ cat thedate

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$ cd

$ ls –l > myhome

$ cat myhome

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$ sort keats

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$ sort < keats

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$ sort < keats > sorted

$ cat sorted

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$ date >> thedate

$ cat thedate

Useful for log files

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$ grep planet keats

When a new planet swims into his ken;

Find all lines containing “planet” in “keats”

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$ cat keats

$ cat keats | grep planet

When a new planet swims into his ken;

Pipes connect output from one command to

the input of another command

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No single obvious choice for editor

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vi – simple but difficult at first

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emacs – powerful but complex

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nano – simple but not really standard

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$ nano keats

“^” means “hold down control”

^a : go to beginning of line

^e : go to end of line

^k: delete line

^o: save file

^x: exit

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$ less /var/log/messages

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Used to read (not edit) files

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Very useful command

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[space] : next page

b : previous page

Shift-g : go to end of file

g : go to beginning of file

^g : display location in file

/ : search

n: repeat search

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$ sleep 5

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More useful than it seems

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$ echo hi

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More useful than it seems

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$ sleep 5; echo hi

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Use ; to separate commands

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$ sleep 600

^c

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Use control-c to stop a running command

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$ sleep 600; echo hi

^c

What happened?  Why?

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$ exit

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Logs out

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There are other ways of logging out

$ logout

$ ^d

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$ ps

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Lists the processes you have running in

this session

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$ ps -e

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List every process

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$ ps -aux

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List every process with a lot more

information

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Flags for ps are numerous and

inconsistent

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$ top

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Lists running processes

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Updates every 3 seconds

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Many options to change display

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Many other top-like commands exist.

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Any questions?

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How Linux Works

by Brian Ward

Available as an 

E-book 

from Columbia

University Libraries and at Safari Books

Online

https://clio.columbia.edu/quicksearch?q=how+linux+works

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Intro to Linux (Youtube)

by Eli the Computer Guy

https://clio.columbia.edu/quicksearch?q=how+linux+works

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You can install Linux as an application on your computer

using VirtualBox which runs within your current operating

system.

How to Install Ubuntu Linux on Windows 7

How to Install Ubuntu Linux on Mac

https://clio.columbia.edu/quicksearch?q=how+linux+works