LabLearningObject-hybrid/Linux-process-management/basics.adoc

= An Introduction to Linux !
Apostolos rootApostolos@swarmlab.io
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:toc-title: Table of contents
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== Absolute basics

.Absolute basics
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|=======================
|Command|	Meaning
|ls|	Displays a list of files in the current working directory.
|cd directory|	change directories
|passwd	|change the password for the current user
|file filename|	display file type of file with name filename
|cat textfile|	throws content of textfile on the screen
|pwd|	display present working directory
|exit or logout|	leave this session
|man command|	read man pages on command
|=======================

=== Key combinations
.Key combinations
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|Key or key combination|	Function
|Ctrl+C|	End a running program and return the prompt
|Ctrl+Z|	Suspend a program
|ArrowUp and ArrowDown|	Browse history. Go to the line that you want to repeat, edit details if necessary, and press Enter to save time.
|Tab|	Command or filename completion; when multiple choices are possible, the system will either signal with an audio or visual bell, or, if too many choices are possible, ask you if you want to see them all.
|Tab Tab|	Shows file or command completion possibilities.
|Shift+PageUp and Shift+PageDown|	Browse terminal buffer (to see text that has "scrolled off" the screen).
|=======================

=== ls -l

[source,bash]
----
# ls -al
drwxrwxr-x 4 zeus zeus  4096 Οκτ  23 21:55 .
drwxrwxr-x 9 zeus zeus  4096 Οκτ  15 14:28 ..
drwxrwxr-x 8 zeus zeus  4096 Οκτ  23 21:55 .git
drwxrwxr-x 4 zeus zeus  4096 Οκτ  14 20:24 install
crw-------   1 root root        5,   1 Οκτ  23 21:22 console
lrwxrwxrwx   1 root root            11 Οκτ  23 21:21 core -> /proc/kcore
drwxr-xr-x   4 root root           100 Οκτ  23 21:22 cpu
crw-------   1 root root       10,  59 Οκτ  23 21:21 cpu_dma_latency
crw-------   1 root root       10, 203 Οκτ  23 21:21 cuse
-rw-rw-r-- 1 zeus zeus  1517 Οκτ  23 21:55 INSTALL.md
-rw-rw-r-- 1 zeus zeus 33883 Οκτ  15 14:28 LICENSE
-rw-rw-r-- 1 zeus zeus   691 Οκτ  17 11:13 README.md
----

==== File types

This table gives an overview of the characters determining the file type:

NOTE: **d**rwxrwxr-x 4 zeus zeus  4096 Οκτ  14 20:24 install

.File types in a long list
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|=======================
|Symbol|	Meaning
|-|	Regular file
|d|	Directory
|l|	Link
|c|	Special file
|s|	Socket
|p|	Named pipe
|b|	Block device
|=======================

NOTE: -**rw-**rw-r-- 1 zeus zeus  1517 Οκτ  23 21:55 INSTALL.md

==== Access rights

.Access rights
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|Code|	Meaning
|0 or -|The access right that is supposed to be on this place is not granted.
|4 or r|read access is granted to the user category defined in this place
|2 or w|write permission is granted to the user category defined in this place
|1 or x|execute permission is granted to the user category defined in this place
|=======================


==== User group codes

.User group codes
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|Code|	Meaning| 
|u|	user permissions|-**rw-**rw-r--
|g|	group permissions|-rw-**rw-**r--
|o|	permissions for others|-rw-rw-**rw-**
|=======================


====  Exercises
[source,bash]
----
touch example
chmod 400 example 
ls -l example
chmod 500 example 
ls -l example
chmod 600 example 
ls -l example
chmod 644 example 
ls -l example
chmod 660 example 
ls -l example
chmod 700 example 
ls -l example
chmod 755 example 
ls -l example
chmod 775 example 
ls -l example
ls -l example
chmod 777 example 
ls -l example
----


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