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Fix permission denied (publickey) when SSH Access to Amazon EC2

I accidentally messed up the /home/ubuntu/.ssh/authorized_keys of AWS EC2, and cannot access EC2 from SSH. Here are the steps for fixing it:

  1. Detach the bad EBS volume.

  2. Create a new EC2 instance, and attach that bad EBS volume to it.

  3. Mount that bad EBS volume from the new created EC2 instance.
    sudo mount /dev/xvdb1 /vol
  4. Fix the /home/ubuntu/.ssh/authorized_keys, and umount and detach the EBS volume.
    sudo umount /vol
  5. Attach the fixed EBS volume to root device /dev/sda1 of the origin EC2 instance.