AWS EC2 instance SSH Connection timed out for port 22

In this post I'll describe one of the connectivity issue that I faced while working with AWS EC2 instance. Below is the problem summary, cause and solution. Let's get started...

Problem
I have created an EC2 Ubuntu Linux instance and configured the same my own. However, I have installed some container application on the same but during the work all of a sudden the SSH connection lost. Now, when I tried to get the connection again , it says-

ssh -L 5901:localhost:5901 -I ssh-key.pem ubuntu@ec2-13-xxx-xxx-139.ap-south-1.compute.amazonaws.com

connection timeout for port 22

Cause
There could be multiple reasons of the same like, inbound rule changes for port 22, firewall turned on, Security group changes etc. In my case it was 'firewall turned on'.

Solution
So how should I go to turn off the firewall without native ssh connection which I do over terminal/putty? The answer is through other was utilities like- 

• Browser based SSH connection
• AWS Systems Manager
• .....

In my case, I have used AWS Systems manager since browser based SSH wasn't working in my machine. Following are the steps I used to connect my linux instance via AWS Systems Manager-

1. Go to AWS Systems Manager-  https://ap-south-1.console.aws.amazon.com/systems-manager
2. 
3. If you have not configured Systems Manager -> Click on Get Started with Systems Manager
4. In my case I have already configured the same so I have Edit option visible there, you might been to configure the same with default options or change as per your requirement. I have configured with the defaults.
5. 
6. Now we re ready with Systems Manager configuration.  So, in order to get SSH connection go back to  https://ap-south-1.console.aws.amazon.com/systems-manager , scroll down and find the section so called Remote Connect and Click on Explore Session Manager.
7. 
8. Next > Click on Start Session Button
9. 
10. Next > Select the instance and Start Session
11. 
12. Next > a new tab will open in browser with SSH connection

So now we need to check the firewall status-

$ sudo ufw status

$ active

Since firewall is turned on so we need to disable it-

$ sudo ufw disable

Check the status again

$ sudo ufw status

$ inactive

Next > Terminate the session and take normal ssh connection from terminal and it should work now-

ssh -L 5901:localhost:5901 -I ssh-key.pem ubuntu@ec2-13-xxx-xxx-139.ap-south-1.compute.amazonaws.com                            

                                                                
Welcome to Ubuntu 18.04.4 LTS (GNU/Linux 5.3.0-1017-aws x86_64)

 * Documentation:  https://help.ubuntu.com

 * Management:     https://landscape.canonical.com

 * Support:        https://ubuntu.com/advantage

  System information as of Wed May 20 08:21:37 UTC 2020

  System load:  0.0                Processes:              263

  Usage of /:   85.1% of 29.02GB   Users logged in:        1

  Memory usage: 42%                IP address for eth0:    172.31.33.26

  Swap usage:   0%                 IP address for docker0: 172.17.0.1
                                                                  

  => / is using 85.1% of 29.02GB

 * MicroK8s passes 9 million downloads. Thank you to all our contributors!
                                                                  

     https://microk8s.io/

 * Canonical Livepatch is available for installation.

   - Reduce system reboots and improve kernel security. Activate at:

     https://ubuntu.com/livepatch

0 packages can be updated.
                           

0 updates are security updates.

Last login: Wed May 20 07:51:18 2020 from 157.38.98.218

ubuntu@ip-172-31-33-26:~$ 

 That's it, our SSH connection is back now!

References-
https://aws.amazon.com/premiumsupport/knowledge-center/ec2-linux-resolve-ssh-connection-errors/
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-console.html
https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager-getting-started.html
https://linuxize.com/post/how-to-disable-firewall-on-ubuntu-18-04/