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2INC0 Operating SystemsIntroduction to Linux

Joris Geurts

practical schedule

week 1:•introduction Linux•introduction C•practical

next weeks:•explanation assignment 1/2/3•practical

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What is Linux?

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characteristics

• developed in 1970'sby Ritchie and Thomson

• multi user• multi tasking

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advantages

• different hardware: IBM, Mips, Intel, ARM• simple structure• elaborate software tooling• command interpreter: the SHELL• principles applied in a consequent way

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disadvantages

• cryptic names, e.g.:cat filename

• cryptic syntax: \ / * $ " ' ` ~ e.g.: grep "*.$1" `pick *.c` | lpr

• many members of the family, and they differ(Debian, Red Hat, Ubuntu, OpenSuse, Fedora, etc.)

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Unix family tree

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Some Unix characteristics

• ‘Everything is a file’– including screen, mouse, hard disk etc.

• All (system) commands are just applications– including login procedure, file and directory management,– large and powerful set of commands

• The central role of the shell (command interpreter)– typing rather than clicking

• Built-in management of different users– multi-tasking and multi-user

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Linux take-off

Linux family tree

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Linux distributions (600+)

kernel + libraries + software applications

Linux desktop environments

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GNOMEGNOME

KDE

Unity

Using Linux: virtualization

• VMware• Linux Ubuntu image

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commands in a shell

interaction with the OS, e.g.:•ls•date•whoami•cal

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Command summary• Commands (find out their functionality)

– ls – mkdir, cp, mv, which, chmod, echo, grep, pwd, cat, ps– man

• input/output redirect– ls > file – command1 | command2 | command3– cat /etc/passwd | sort | less– less /etc/passwd

• editors– kate, gedit, vi– (to be installed) emacs, joe, nano, eclipse

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Practical assignments (shell)• Startup and login to the system

– Username: student Password: student

• Create a directory in– Your home directory (/home/student/)

– The temporary directory (/tmp/)

– The root directory (/)

• Copy the password file to your home directory

• Search where the ls binary is located– Determine its owner and permissions

– Record this information in a file

• Do a tutorial• Install Dropbox (via Software Center)

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C programming language

• Language of the Linux kernel and many of the applications

• Low-level– No memory protection

– No garbage collection

– No decent string type

– Direct memory pointer manipulation

• High execution performance possible– At the cost of a longer development time

importance of C

18source: www.langpop.com

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Hello World

• see http://www.fhict.nl/docent/downloads/2INC0/

• compile and run

$ gcc -o helloworld helloworld.c

$ ./helloworld

• printfint i = 73;

printf ("Hello World\n");

printf ("decimal display: %d\n", i);

printf ("hexadecimal display: %04x\n", i);

• debugger…

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Debugging with nemiver

• sudo apt-get install nemiver (only once; already done)

• gcc -g –Wall –o myapp myapp.c

• nemiver myapp &– set breakpoints– run, step, etc.– inspect variables

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Pointers in C

roughly said:•C pointer =Java reference•C struct =Java object with public variables, without methods

Practical: see the comments in helloworld.c for extra assignments