A key pair in AWS EC2 is used to secure SSH access to an instance:

Definition:

• A key pair consists of a public key and a private key.
• AWS stores the public key on your EC2 instance, while you keep the private key secure on your own computer.

Purpose:

• The private key enables SSH access to log into your instance securely.
• This key-based authentication is more secure than password-based login and ensures that only authorized users with the private key can access the instance.

Creating a Key Pair:

• Key pairs can be created directly in the AWS Management Console, CLI, or SDKs.
• AWS only allows you to download the private key once, so it’s essential to save it securely.

Using a Key Pair:

• When launching an instance, you associate it with a key pair.

• To connect to the instance, you use SSH and specify the path to the private key file, like so:

  ssh -i /path/to/your-key.pem ec2-user@instance-public-dns
  

Best Practices:

• Secure Storage: Keep the private key secure and restrict access to it.
• Backup: Avoid losing the private key as it is needed for instance access. If lost, access to the instance might require a new key setup.
• Use IAM Roles for Programmatic Access: For applications on EC2 that need to interact with AWS services, use IAM Roles instead of embedding keys in your code.