Wednesday, April 29, 2020

How To recover keys or connect to EC2(EBS) instance via user-data


In this post, let us see how to recover keys for EC2 instance(EBS) whose keys is lost 

Pre-requisites:
  • AWS Account login and access
  • Permission or access to launch EC2

Getting Started :
  • Create an EC2 of your choice(I use Amazon Linux2 here); note that i dont have any role attached to this 

 The above instance is the key pair is lost
  • Create a new key pair from AWS EC2 Console
 

   Key pair will be created will look like this


  • Generate private key from this key pair; Connect to puttygen and open the acg-amz.pem file which is just generated and downloaded in local. Click on generate 'Public key' save it as 'acg-amz.ppk' to connect to putty connections


  • stop the instance now to amend the user data 



  • Select the instance, click on Action -> Instance settings -> View/Change user data. Copy the below data


  • Start the instance and connect using SSH and see the connection taken successfully, because the new public key has been copied via user data

 Note:
  1. If the user data is not getting applied, then amend the [user-groups, once] tp [user-groups, always]
  2. Generate public key using puttygen or from ssh-keygen module from any other instance and use the same in user data
  3. IP Address might change when this process takes place
 

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