written By: Rahul Goraksha

In this blog, we will look at the fundamentals of SSH and SCP, their functions, and their importance in today's digital world.

Figure 1: Schematic Diagram of SSH Protocol

What is Linux?

Linux is a free open-source operating system (OS) that provides more security than many operating systems and does not require antivirus software for protection.

So, let's first understand the layers of Linux Architecture:

It mainly consists of four layers which are Hardware, Kernel, Shell, and Application.

Figure 2: Linux Architecture

Application: There are various applications such as web browsers, media players, etc that users install and tend to use on their Linux systems.

Shell: It is a program that interprets user commands and allows communication between the user and the kernel of the operating system.

Kernel: It mostly acts as a doorway between the Shell and hardware and performs communication between software and hardware components.

Hardware: It mainly use to interact with the real physical world for example print, output, etc.

So After having a thorough understanding of Linux architecture, let's head on to understanding the SSH Protocol

What is SSH Protocol?

SSH stands for secure Shocket shell.

If we want to work with multiple servers, then there will be a Linux Shell, the kernel is already present, so directly connect to the shell and get access to all the servers and perform what you wish.

How do I connect Shell in a very secure manner?

Figure 3: SSH Protocol Explanation

To connect Shell in a very secure manner, there are mainly three major parameters being followed throughout the industry, and those are as follows:

1. Username, Password

2. Keys ****{Popular Method}

3. Role-Based Access Control

Figure 4: Classification of Keys

Keys have been classified into two categories:

Private Keys: Private keys stay with the user only

Public Keys: Public key is mainly sent to the server

with reference to the above Figure 3 if both private and public keys are paired then only it's possible to generate the keygen

So if we want to connect the Shell securely for that we need to get the private key from the Server and in exchange for that User_1 needs to provide the public key to the Server after getting paired successfully we are good to perform any operations.

Initially, you need to download the private key of a particular server. Then, you have to grant permission to access the private key.

Now let's get hands-on experience by practicing using the below command

Running this command to ensure the private key is not publicly viewable

chmod 400 linux-for-devops.pem

Next, we need to connect our server using its Public DNS

ssh -i privatekey username@host[ipaddress]

You will be connected to a distant server after running this command on your local PC.

What is the SCP Protocol?

SCP stands for "Secure Copy Protocol", In these operations, we securely copy files from a distant server into our local system or vice versa. During this operation, we employ the SCP protocol.

let's understand this protocol with a hands-on example

scp -i "file_name".server DNS name:/path local_dir_path

After executing this task, we get the desired output as required.

Thank you for being a part of this adventure once more. I want to connect with you in future blog postings. Continue to be interested, inspired, and evolving.

Rahul Goraksha