AWS EC2 Cloud Init - Used when you lost key to ssh to your EC2 instance

aws-ec2-cloud-init-users.md

Add this to your instance user data. You need to stop the instance before set this.

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#cloud-config
cloud_final_modules:
- [users-groups, once]
users:
  - name: <username>
    shell: /bin/bash
    sudo:  ALL=(ALL) NOPASSWD:ALL
    ssh-authorized-keys: 
    - ssh-rsa <public-key-goes-here>