The default method to access Linux EC2 instances on AWS is via SSH, and only the public-key authentication method is configured on the EC2 instances.
The public SSH key is added automatically to the EC2 instance when created, and you should be given the SSH private key in PEM format when creating the EC2 instance. The same is true for either Red Hat or Ubuntu-based EC2 instances.
SSH client is typically included in the default installation of Linux or other Unix-based operating systems, but not so in some versions of Windows. One popular SSH client that you can use to log in to your Linux EC2 instances from Windows is PuTTY.
Steps to SSH to Linux AWS EC2 instance using PuTTY:
Make sure the security group of your
EC2 instance is configured to allow
SSH connection from your current host, or use a
VPN or proxy server if necessary.
Convert the provided
PEM private key file to
PPK (
PuTTY Private Key) format.
Download
PuTTY from the official website.
https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html
Launch
PuTTY.

Enter the
Host Name or
IP Address of your
ec2 instance.

Go to
Connection →
SSH →
Auth from the sidebar menu.

Click on the
Browse button to look for your
PuTTY Private Key.

Select your
PuTTY Private Key from the stored location and click on the
Open button.

Click on the
Open button to start the connection.

Click
Yes if a security alert pops up as this is your first connection to the server and the server's key fingerprint is not in your
PuTTY's cache.
Enter the username that you want to connect as and press enter.

Enter the passphrase for the key if a passphrase protects your key.

You should now are logged in using the public key authentication to the system.

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