How to connect the AWS EC2 instance if lost your SSH key pair

4 min readFeb 3, 2023

Overview:

Losing access to your Amazon Web Services (AWS) Elastic Compute Cloud (EC2) instance can be a frustrating experience, especially if you’ve lost the SSH key pair that you normally use to log in. However, there is a solution. In this article, you’ll learn how to regain access to your EC2 instance( Linux Instance) if you’ve lost your SSH key pair. This process involves creating a new key pair and using it to log into your EC2 instance and update the authorized keys file. With the steps outlined in this article, you’ll be able to regain access to your EC2 instance quickly and easily.

1st I will create an ec2 instance for demo purposes.

lost Key pair name: ec2-missing-kp

Unfortunately, losing access to your EC2 instance can happen even when you’re trying to create a new one and set up a new key pair. By following these steps, you’ll be able to regain access to your EC2 instance even if you’ve lost the key pair associated with it.

This section of the article could provide a step-by-step guide on how to regain access to the EC2 instance in this situation, with screenshots and clear instructions to help readers understand the process.

Step 1:

Create new Key Pair

1.1 Go to the EC2 console and under the Network and Security section, select key pair option.

2. Select create new Key pair

Create Key Pair

3. create new key pair. In my case, my new key pair name is “ec2-missing-new-kp”.

Step 2:

2.1. Now you can go to your local terminal and under the switch to the directory way, a new key pair file is downloaded.

After that type this command:

ssh-keygen -y -f filename.pem

Now we got our public key. So this public key wants to put our ec2 in the future. keep this safe.

2.2 Get this script and modify it.

Content-Type: multipart/mixed; boundary="//"
MIME-Version: 1.0

--//
Content-Type: text/cloud-config; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="cloud-config.txt"

#cloud-config
cloud_final_modules:
- [users-groups, once]
users:
  - name: username
    ssh-authorized-keys: 
    - PublicKeypair

Now you want to some changes to this script. Under the users: section firstly you need to rename your ec2 user name. In my case my ec2 user name is ec2-user. You can confirm this by going to EC2 connect section( I attached an example screenshot for your reference)

Note: You need to verify your username correctly.

After that in the ssh-authorized-keys section, replace the public key pair you got earlier here. The key which we have created(step 2.1)

Content-Type: multipart/mixed; boundary="//"
MIME-Version: 1.0

--//
Content-Type: text/cloud-config; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="cloud-config.txt"

#cloud-config
cloud_final_modules:
- [users-groups, once]
users:
  - name: ec2-user
    ssh-authorized-keys: 
    - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDTbmAuTDxr+2AHf3xgGizTErbIz4EglR7YgPO1c0XaQ+6Y8oCgJrs/gXm371fooGYaA/Uzc7AEM5aTNbGCiBbPWSP/GqsSyJTi4tkUrA7+88Z7RYR3bgBptdw3ZXMgXklMwBbp1gf8Dz6E9dHWBt2O6SrqGu63CjJyaG9pJd0crPYX3hBt0yn6zJ7E9QQbKi1Ar/ZZ4KPBxByRpLsqHutoltGgATeHmMQm/Krm5MnuUv9vdzMsVDlxBfKpfRStn7ZXlui5g5bAAgD4ML+SwZ78d7RxQTaYHwaDAEtVsBqA+f/deb4wQTjZXrBRKtl9nl+yRsJkGJbP7mat3AARkE3F

Step 3:

3.1. Now go to the AWS Management Console and stop your ec2 instance. (Keep in mind, If you do not attach elastic IP, your public IP will change during reboot)

Now select the ec2 instance and under the actions, tab go to the instance settings.