The basics

 change the current directory

cd ~/code/ruby/ror/my_project

The long way

The short way

cd ~/c/r/ro/my_pro + tab

Thanks Zsh

Create a folder

mkdir -p project1/code project2/presentation

mkdir : create a folder

-p : create also the subfolders

it create:

current folder -> project1    -> code

current folder -> project2    -> presentation

Create and edit a file

create a file: touch

touch my_file

Edit the file: nano 

nano my_file

Save with CTRL + O and exit with CTRL + X

See the content of a file

cat my_file.txt

The owners

The super user : root

Try:

apt-get update

Permission non accordée / Permission denied

Result:

Now do it with a sudo

sudo apt-get update

=> if you don't have the permission to do something , you can do it with the root permissions

Create a folder with the root permissions

sudo nano a_file.txt

exit and open this file with a simple nano

=> you don't have the permission , if the root user create something, the simple user don't have any permissions to this file

List the files

ls -l

list all the files with the permissions

The file is owned by the root user (and the root group)

Change the owner

sudo chown jc:jc hy.txt

now , the owner of the file hy.txt is jc and the group jc

you can find your user name with the command 

whoami

you can change the owner of a directory with the argument : -R

sudo chown -R jc:jc a_folder

if you will change the owner of a file , you NEED to be the owner of the file

Manage the users

Add a user 

Delete a user

passwd JohDoe

Change the password of a user

 adduser JohnDoe

deluser JohDoe

Permissions

Read-Write-Execute

d = directory

(- = file )

Read

Write

Execute

The owner

Read

Write

Execute

The group

Execute

Other 

Change the permissions

example:              7       3          0                      

       owner-group-other

Change the permissions

(sudo) chmod 777 my_file.txt

For a file

For a directory (and his files)

(sudo) chmod 777 *

For a everything in a file

(sudo) chmod -R 777 my_direcotory

For a everything in a file and in his directory

(sudo) chmod -R 777 *

Some usefull commands

Remove files and directorys

Never run this command

sudo rm -rf /*

=> it delete everything (your OS, your files)

Ping a website

=> it give the ip of a website, and it say if you are connected to the network

Stop the command with CTRL+C

Your network status

ifconfig

Ethernet connexion

= eth0

Wifi connexion

= wlan0

My local ip (ipv4) address

My local ip (ipv6) address

My mac addres (not real)

My local connexion (useless)

Change your macaddress

Your mac address is uniq so it isn't very good for your Privacy Policy but you can very easy change your mac address, it's usefull 

for your privacy , free wifi hotspot with time and for some problems with internet connexion

examples of mac address:

09-74-A3-D4-D1-43

ED-40-74-9F-EA-8A

BA-89-E7-1E-92-F4

.......

Change your macaddress on ubuntu

sudo nmcli connection modify --temporary the_wifi_name 802-11-wireless.cloned-mac-address mac_addr

#then you do : 
nmcli connection up wifi_name

Change your macaddress on apple

sudo ifconfig en0 xx:xx:xx:xx:xx:xx

Enjoy your terminal (and your privacy)