Understanding SSH and Establishing Connections in DevOps

SSH, or Secure Shell, is a crucial tool in the world of DevOps for securely accessing remote machines. Let's break down how it works and how you can use it to connect different machines.

What is SSH?

SSH stands for Secure Shell and it allows you to securely connect to a remote machine over an unsecured network. It provides encrypted communication between two hosts over an insecure network.

Public and Private Keys

One of the key concepts in SSH is the use of public and private keys for authentication. When you want to connect from machine A to machine B:

Machine A (Client): Uses its private key to initiate the connection.
Machine B (Server): Holds the corresponding public key of Machine B to authenticate and allow the connection.

This ensures that only authorized machines can establish connections.

Connecting to AWS from a Physical Machine

To connect to an AWS instance (jump server) from your physical machine:

Launch AWS Instance: Start an instance on AWS.
Download Private Key: Download the private key provided by AWS.
Set Permissions: Change the permissions of the private key file to restrict access (chmod 400 private-key).
Open Terminal: Navigate to the directory where the private key is stored.
Establish Connection: Use SSH to connect to the AWS instance:
```
 ssh -i private-key ubuntu@server-dns-address
```

Connecting Between AWS Instances

To connect from Machine A to Machine B on AWS:

Machine A: Generate a new SSH key pair (private and public key).
```
  ssh-keygen
```

Machine B: Add Machine A's public key to the authorized_keys file.

  cd .ssh
  vim authorized_keys
  # Paste Machine A's public key, save and exit

After configuring both machines, you can connect from Machine A to Machine B using:

ssh -i private-key ubuntu@server-dns-address

Conclusion

Understanding SSH and how to establish secure connections between machines is fundamental in DevOps. By using public and private keys, you ensure secure authentication and communication. I hope this blog post helps you navigate these concepts effectively!

If you have any questions or feedback, feel free to reach out. Happy learning in your DevOps journey! 🚀