*Launching and Connecting to a Linux EC2 Instance

Summary

In this lab I created an Amazon Linux EC2 instance in AWS, configured its networking and security group, created a key pair, and connected to the instance over SSH from the Windows Command Prompt using the .pem key file and the instance's public IP address.

Lab Environment

Part 1: Launch the Instance

1. Open EC2

I searched for EC2 in the AWS Console, opened the EC2 dashboard, went to Instances, and clicked Launch instances.

2. Name the instance

Under Name and tags, I entered the name MyFirstLinux.

3. Choose the AMI

Under Application and OS Images (Amazon Machine Image), I selected Amazon Linux from the Quick Start tab. Unlike the Windows lab, I didn't need to browse more AMIs, since Amazon Linux is the default option.

Note: When selecting an AMI, note down the default SSH username displayed on the AMI details page. Different AMIs use different usernames: Amazon Linux uses ec2-user, Ubuntu uses ubuntu, Debian uses admin, and so on. We'll need this username to connect via SSH later.

4. Choose the instance type

I selected t3.micro, which provides 2 virtual CPUs and 1 GiB of RAM and is free tier eligible. On-demand Linux pricing for this type is lower than Windows because there is no Windows license cost.

5. Create a key pair

Under Key pair (login), I clicked Create new key pair and used these settings:

• Key pair name: demo
• Key pair type: RSA
• Private key file format: .pem (for use with OpenSSH)

After clicking Create key pair, the demo.pem file downloaded automatically to my Downloads folder. I saved it, because it is the only way to log in to the instance over SSH and AWS will not let me download it again.

6. Configure network settings

I clicked Edit in the Network settings section.

• VPC: I kept the default VPC.
• Subnet: I selected the subnet in ca-central-1a. The Mumbai region has three Availability Zones (ca-central-1a, ca-central-1b, ca-central-1d). If no subnet is chosen, AWS picks the Availability Zone automatically.
• Auto-assign public IP: Enabled, so I can reach the instance from my computer.

7. Configure the security group

I chose Create security group and kept the name AWS generated (it can be changed if needed). For Linux instances, AWS adds an inbound rule for SSH by default:

Extra inbound rules can be added here if needed (for example HTTP on port 80 for a web server).

8. Configure storage

I kept the default 8 GiB gp3 root volume (3000 IOPS). The root volume is like a laptop's hard drive: it's where the operating system is installed. Linux needs much less space than Windows, which defaulted to 30 GiB in the Windows Lab. Free tier accounts get up to 30 GB of EBS storage.

9. Launch

I clicked Launch instance, then went back to the Instances page and waited until the instance showed Running with 3/3 checks passed.

Part 2: Connect Using SSH

Since the security group only allows SSH, I connected through the command line instead of a graphical desktop.

1. Copy the public IP

I selected the instance and copied its Public IPv4 address from the Details tab.

2. Open Command Prompt and go to the key's folder

The demo.pem file was in my Downloads folder, so I opened Command Prompt and moved into it:

cd Downloads

3. Connect with SSH

I ran the ssh command with the key file (-i), the default Amazon Linux user (ec2-user), and the public IP:

ssh -i demo.pem ec2-user@PUBLIC_IP_ADDRESS

4. Accept the host fingerprint

On the first connection, SSH warned that the host's authenticity couldn't be established and showed its ED25519 fingerprint. I typed yes, and the host was added to my list of known hosts.

5. Logged in

The Amazon Linux 2023 banner appeared, followed by the shell prompt:

[ec2-user@ip-xxx-xxx-xxx-xxx ~]$

I was now connected to the Linux instance and could run commands on it.

Key Takeaways

• Amazon Linux is available directly from the Quick Start AMIs.
• Linux instances are accessed through SSH on port 22, while Windows instances use RDP on port 3389.
• Linux doesn't need a decrypted password: the .pem private key is used directly to log in.
• The default username for Amazon Linux is ec2-user (other AMIs differ, for example ubuntu for Ubuntu).
• The default Linux root volume (8 GiB gp3) is much smaller than the Windows one (30 GiB).

Troubleshooting

• "Permission denied (publickey)": check that you're using the right key file and the ec2-user username.
• "UNPROTECTED PRIVATE KEY FILE" or "bad permissions": the .pem file is readable by other users. On Linux or macOS, run chmod 400 demo.pem. On Windows, remove other users' access to the file in its Properties → Security settings.
• Connection timed out: confirm the instance is running, has a public IP, and the security group allows port 22.

Security Notes

• Allowing SSH from 0.0.0.0/0 lets anyone on the internet attempt to connect. For real use, the source should be limited to My IP.
• The .pem file should never be shared or committed to a repository.

Cleanup

To avoid charges after the lab, terminate the instance from Instance state → Terminate instance, and delete the security group and key pair if they are no longer needed.