Lecture #6: Linux basics

7/27/2019 Lecture #6: Linux basics

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High performance computing

for non-programmers

Lecture #6:Linux basics

Glib Ivashkevych

junior researcher, NSC KIPT


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Hardware vs. Software

HW

physical elements of computing system

CPU, memory, system bus, HDD

SW

machine readable instructions that tell HW to performspecific task

OS, system software, application software


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Operating system

why?

Manages hardware resources

Provides services for application software

Processscheduling

and others


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Unix

This is the Unix philosophy: Write programs that do one

thing and do it well. Write programs to work together.Write programs to handle text streams, because that is a

universal interface.

Doug McIlroy, developer of Unix pipes
http://en.wikipedia.org/wiki/Standard_streamshttp://en.wikipedia.org/wiki/Computer_program


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Unix

the power of Unix Way

Imagine this:

You have thousands of data files, one per experiment.

Each file contains thousands of measurements.

Some values are wrong, and are denoted as nan.

Files and data lines are numbered conveniently.

Find which measurements in which experiments had

fallen.


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Unix

the power of Unix Way

Shell oneliner solves this. And it solves it

fast.

It uses just grep,cut,sedand pipes


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Unix (and Linux)

shellShell is a way to communicate with system.

Shell accepts commands from user (or from script).

Also shells have programming language constructs

(loops, conditionals, variables, etc.)

Most of *nix OS functionality is launched via shell scripts(including windowing system).


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Unix (and Linux)

first ever login

Whoam I?

Wheream I?

Where is my stuff?

whoami

pwd

ls, cd


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Unix (and Linux)

users

*nix systems are multiuser

Each user has:

id (UID)

group id (GID)this is defaultgroup

home directory (usually /home/username)


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Unix (and Linux)

permissionsTo shield users from each other, each file haspermissions

7 4 4

-rwxr--r-- 2 user group ...

filetype

owner

group

others

group

name

owner

name

hardlinks

r (4)- read

w (2)- write

x (1)- execute


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Unix (and Linux)

directory structureHierarchical organization

Singleroot /

Home directories usuallyin/home

. means current directory

.. means parent directory


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Unix (and Linux)

directory structure

/bin mission critical binaries

/bootfiles for system boot

/dev device files (yes, devices are seen as files in *nix)

/etc config files (yes, config files are just text files)

/homeusers home directories

/lib mission critical shared libraries

/procprocesses (virtual files)


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Unix (and Linux)

directory structure

/tmptemporary files

/usr generally, user binaries and libs (sic!)

/varlogs, etc.

FHS for Filesystem Hierarchy Standard


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Unix (and Linux)

paths & names

path from root is absolute(e.g. /home/username/docs)

path from some dir is relative(e.g. .. fromdocs is

/home/username)

Names:

everything except /, no - at the beginning, but

be careful


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Unix (and Linux) shell

typical operations

Work with filesdata

Launch programsinstructions

Admin system (well do this later)

You also need to navigatewell start here


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navigatingls- list directory

useful options: -l -a -A (you can use -la)

cd- change directory

without argument changes to home dircd ~is the same as just cd


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create files and dirstouch- modify timestamp or create

useful options: -c -a -m

mkdir- create directory

useful options: -p -m (--mode=MODE)


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look inside filescat- concatenate and print files

useful options: -n -b

head, tail, less- get content of file

head useful options: -c [-]K -n [-]K

tail useful options: -c [+]K -n [+]K -ffile- get file type

useful options: -i -s


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copy/move files and dirscp- copy files and dirs

useful options: -i -r --preserve[=ATTRS]

be careful: -f

mv- move files and dirsuseful options: -u -i


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remove files and dirsrm- remove files

useful options: -i -r

be careful: -f

rmdir- remove dirsuseful options: -p

be careful:--ignore-fail-on-non-empty


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change owners and modechmod- change mode of file or dir

useful options: -R

chown- change owner of file or dir

useful options: -R


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optionsGeneral syntax:

[OPTIONS] [PARAMS]

Shortkeys:

-k, -k [VALUE]

Longkeys:

--some-long-key[=VALUE]


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shortcutsCTRL-f, CTRL-b - one char forward/backward

CTRL-a, CTRL-e - to the beginning/end of line

ALT-f, ALT-b - one word forward/backward

CTRL-] x, CTRL-ALT-] x - forward/backward to nextoccurrence of x

!!,!!:p- execute/print last command

!$,!^- last/first argument of last command


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Lost in translationshell

where to get help?-helpor -h options

man command

(say man ls to get help on lscommand)

aproposcommand

infocommand

/usr/share/doc


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Questions?

Lecture #6: Linux basics

Documents

Transcript of Lecture #6: Linux basics