1896 1920 1987 2006

Mini Introduction to Linux

LT Kong （孔令体）

Dec 18th, 2019

LingTi Kong, konglt@sjtu.edu.cn 2

Operating System

An operating system (OS) is system software that manages

computer hardware, software resources, and provides common

services for computer programs.

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Linux is a Unix clone written from scratch by Linus Torvalds with

assistance from a loosely-knit team of hackers across the Net.

Unix is a multitasking, multi-user computer operating system originally

developed in 1969 by a group of AT&T employees at Bell Labs.

64% of the world’s servers run some variant of Unix or Linux. The

Android phone and the Kindle run Linux.

Network based

What is Linux?

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Linux Distributions

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UbuntuKylin

http://www.ubuntukylin.com/

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Remote connection

CMS Server info:

Address: 202.120.49.140

Port: 1022

Username: user???

Password: CMSWin?????

http, ftp, ssh, …

putty, winscp, powershell, MobaXterm

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MobaXterm

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Directory

Directories can hold files and other directories

/

bin etc hometmp

backup

user1user2

… …

usern

public_html

file1

index.html

root

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PermissionsPermission owner group size modification-time name

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A shell is a computer program that interprets the commands you type and

sends them to the operating system. Secondly, it provide a programming

environment consisting of environment variables.

To determine your shell type:

echo $SHELL (shell prints contents of env)

echo “$SHELL” (shell still processes env. variable)

echo ‘$SHELL’ (shell treats env. variable as simple literal)

To determine the path to the shell program, type:

which bash

Shell

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UNIX/Linux paths

“~” (tilde) points to the user’s home directory. Useful if you are logging into a workstation with many users.

Many of the other paths are inaccessible and unimportant to you

~ is the default working directory when you log in.

If you are user “usern”, then /home/usern/file1 is the same as ~/file1.

“.” refers to the current directory

“..” refers to the parent directory.

If you are in /home/usern/, then ../ refers to /home/.

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Basic commands

man: manual. Use “man command” to bring up a manual entry for command or

program command.

clear: clear. Clears the screen.

ls: list. Lists folders/files in a directory

cd: change directory.

Use “cd name” to navigate to directory name.

pwd: print working directory. Prints the path of the current directory.

cd -: go back to the previous directory

echo: display line of text/string that are passed as an argument

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More commands

mkdir: make directory. Use “mkdir name” to create a new directory in the current

directory named name.

cp: copy. Use “cp src dest” to create a new file, dest which is a copy of src. Can

also use “cp srcs directory” to copy all src files to directory.

mv: move. Same as copy, but deletes the original file.

rm: remove. Use “rm file(s)” to delete files

rmdir: remove directory. Use it to delete an empty directory

You can not get your files back after removing them!

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More commands

cat: concatenate files and displays the output to the standard output

seq: Print numbers from FIRST to LAST, in steps of INCREMENT.

Pipe and redirection:

cmd1 | cmd2: cmd2 will take the output of cmd1 as its input.

cmd1 > filename: the output of cmd1 will be redirected to a file named filename; if filename

exists already, it will be rewritten.

cmd1 >> filename: the output of cmd1 will be redirected to a file named filename; if filename

exists already, it will be appended.

cmd1 < filename: the input of cmd1 will be read from a file named filename.

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Some tips

“tab” for auto-complete.

Partly type in a file/directory name, tab will auto-complete it

“*” “?” is used as a wild card.

“rm blah*” removes all files start with blah

“rm blah?” removes all files start with blah and with one extra letter/number.

Using “cp public/* private/” copies all files in your public directory into your

private directory, and keeps all file names intact.

Always be careful with “rm -f *” and/or “rmdir -f *” and/or “rm –rf *”

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Shell programming: script Script: a collection of commands/programs to run.

Loop:

• for var in list; do; things to do repeatedly; done

Branches:

• if condition then; things to do; else; other things to do; endif

Variable substitution:

• varname=“var-value”

• ${varname} or $varname

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Programs

Some basic/common UNIX programs:

emacs: text editing

vim: text editing

gcc: C compiler

gfortran: fortran compiler

gnuplot: 2D drawing and scripting; data fitting

LaTeX: A document preparation system, a high-quality typesetting system

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Job submission on clusters

In general, a queueing system is needed for large computer clusters to

use the computational resources efficiently/fairly/economically.

PBS/Torque is used on CMS.

• Job submission:

• qsub: native command, man qsub

• submit: convenient script, submit –h

submit –n 4 lmp

submit –n 4 –S ./run

• Job status: qstat

• Cancel job: qdel job-id

1896 1920 1987 2006

Enjoy & Thanks