Mona-Roza/linux_101

This repo contains Linux basics.

LINUX 101

Getting Started

In this section we'll talk about the key pairs, commands and packages when we are using server. If you have any ideas or feedbacks about my notes, you can type in issues, you'll help me and the other learners.

Create Instance with AWS

If you want to use this service, you should log in your AWS console.

After logging in your console you should follow these tab parts:

Services->Compute->EC2->Launch instance

In this tab, you can create a new instance/machine. We are using Ubuntu 18.4. So what we will talk about in the other sections will be explained through this version of ubuntu. After this explanation we can flow directions:

! This directions explain AWS free services. If you need different system requirements, you can change your system elements except the operating system.

1. Firstly choose name for your server:

   

2. Choose your machine's operating system like that:

   

3. Choose your instance type like that:

   

4. We need a key pair because we can't create password for root user when we are creating our server:

   

5. When you are creating your key pair, you should be careful about your key's extension. Because you need your_key.ppk file. But if you hadn't created your key with .ppk extension, don't worry about that. Because, I will explain converting your key file from .pem to .ppk in the other section.

   

6. If your Summary part like that, we can launch our instance:

   

Converting key pair using PuTTy

In this section we'll convert our key with .ppk extension to key with .pem extension. But before go on the section, you need PuTTy application. So you should install PuTTy.

1. Start PuTTygen.

2. Open your file with .pem extension with using Load button. After that, you can click the save public key button.

   

3. Save public key with Save button. But don't forget where you save.

Connect with PuTTy

In this section we'll access our server with our key pair, remove with accessing key pair, allow accessing with password and create a password for root:

1. Your ip here:

   

2. Follow Connection/SSH/Auth path and browse directory where you saved your key. And after that Click open button.

   

3. You should login as ubuntu where opened command line window: login as: ubuntu

4. Start editing ssh_config file with sudo nano /etc/ssh/sshd_config command.

5. Find PasswordAuthentication permission and change the value to yes. After that append this permission : PermitRootLogin yes

6. Close and save editing the file with CTRL + X shortcut.

7. Create password for root with this command: sudo passwd root

8. We changed permissions so we have to restart sshd service. Use sudo service sshd restart or sudo systemctl restart sshd command.

9. Update your system with this command: sudo apt update && sudo apt upgrade -y Also run this command whenever you log in your server.

   ! If you want to add user, you can follow next steps.

10. Create a user with sudo adduser user-name command.

11. You can change this user's permissons with sudo usermod -aG sudo user-name command. This command gives root permissons to your user.

12. You can change password for your user with sudo passwd user-name command.

With this directions we edited our machine's permissions for accessing with password. After that we can access our server with using any SSH client for Windows machine or with using ssh root@ip-address command in your machine's command line for MacOS or Linux machine.

Some Commands on Linux

Command	Description
apt remove package_name	Deletes package_name package
apt purge package_name	Deletes the residual files of the package named package_name
sudo ufv status	Checks if the firewall is active
sudo ufw allow port_number	Firewall allows port named port_number
sudo ufw enable/disable	Activate/deactivate the firewall
mkdir folder_name	Creates folder_name folder
touch file_name	Creates file_name file
cp file1.extension file2.extension	Overwrites file1 with file2. file1 is preserved
mv file1.extension file2.extension	Overwrites file1 with file2. file1 is not preserved
screen	Openes a screen. You can exit screen with CTRL+A+D shortcut (But your screen isn't killed)
screen -ls	Lists open screens
screen -r screen_number	Opens screen_number screen
CTRL + A and then pres K	Kills the open screen
zip -r file_name.zip *	Zip all files in the folder it is in
unzip file_name.zip	Exports file_name.zip
top	Monitorizes all processes and process numbers, if you want to monitorize your ram usage, you can press F in this screen after that select MEM with arrow keys, save with S key and turn back with Q key.
kill -9 process_number	Terminates process with its process_number