Connecting to EC2 instances in AWS - Step-by-Step Execution

Process Flow - Connecting to EC2 instances

Start: User wants to connect

↓

Check: EC2 instance running?

No→Start instance

Yes↓

Obtain instance public IP

↓

Use SSH client with key and IP

↓

Authenticate connection

↓

Access EC2 instance shell

↓

End

This flow shows the steps to connect to an EC2 instance: ensure it is running, get its IP, use SSH with the key, authenticate, and access the shell.

Execution Sample

AWS

ssh -i MyKey.pem ec2-user@54.123.45.67
# Connects to EC2 instance using SSH and private key

This command connects your computer to the EC2 instance at IP 54.123.45.67 using the private key file MyKey.pem.

Process Table

Step	Action	Check/Command	Result/Output
1	Check if EC2 instance is running	aws ec2 describe-instances	Instance state: running
2	Get public IP address	aws ec2 describe-instances --query 'Reservations[].Instances[].PublicIpAddress' --output text	54.123.45.67
3	Run SSH command	ssh -i MyKey.pem ec2-user@54.123.45.67	Connecting...
4	Authenticate using private key	SSH client uses MyKey.pem	Authentication successful
5	Access EC2 shell	Shell prompt appears	User logged into EC2 instance
6	Exit connection	exit command	Connection closed

💡 Connection ends when user types 'exit' or disconnects

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	Final
EC2 Instance State	unknown	running	running	running	running
Public IP	none	54.123.45.67	54.123.45.67	54.123.45.67	54.123.45.67
SSH Connection	not started	not started	connecting	connected	closed

Key Moments - 3 Insights

Why do I need the private key file (MyKey.pem) to connect?

The private key file is used to securely authenticate you to the EC2 instance. Without it, the SSH connection will fail (see Step 4 in execution_table).

What if the EC2 instance is not running?

You must start the instance before connecting. The flow checks instance state first (Step 1). If not running, start it to get a public IP and accept connections.

Why do I use the public IP address in the SSH command?

The public IP is the address your computer uses to reach the EC2 instance over the internet (Step 2). Without it, SSH cannot find the instance.

Visual Quiz - 3 Questions

Look at the execution_table, what is the EC2 instance state after Step 2?

A stopped

B pending

C running

D terminated

💡 Hint

Check the 'Result/Output' column for Step 1 and Step 2 in execution_table.

At which step does the SSH client authenticate using the private key?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Look for the 'Authenticate using private key' action in execution_table.

If the EC2 instance was stopped initially, which step would change?

A All of the above

B Step 3 would fail to connect

C Step 1 would show 'Instance state: stopped' and require starting instance

D Step 5 would not show shell prompt

💡 Hint

Consider what happens if the instance is not running before connection attempts.

Concept Snapshot

Connecting to EC2 instances:
1. Ensure instance is running.
2. Get its public IP address.
3. Use SSH with your private key file.
4. Authenticate and access the shell.
5. Exit when done.

Full Transcript

To connect to an EC2 instance, first check if it is running. If not, start it. Then find its public IP address. Use an SSH client with your private key file to connect to that IP. The SSH client authenticates you using the key. Once connected, you get a shell prompt on the EC2 instance. When finished, type 'exit' to close the connection.