AWS EC2: Re-generate pub_private key value pair

# If you accidentally deleted your server's ".ssh/authorized_keys" then follow below steps

# lost key instance => lost_ec2
# new launched instance => new_ec2
step 1: launch new ec2 instance and generate new .pem(new_pem.pem) file.

step 2: stop lost_ec2 instance and dettache volume.
step 3: attach lost_ec2 volume to new_ec2 volume.

step 4: log in to new_ec2 using new_pem.pem file.

step 5: follow these steps..
  mkdir /mnt/recovery
  #Mounting the volume using the previously annotated parameter as first argument
  mount /dev/sdf(enter new name asxvdf if any error) /mnt/recovery
  #Substituting the authorized_keys file with the new one.
  #This way any new access to the new instance will be possible only using the new pem.
  #This command assumes we are operating on an Amazon Linux instance
  #Using other Linux flavors we might have to change the path or the name
  #of the authorized_keys file.
  cat /home/ec2-user/.ssh/authorized_keys > /mnt/recovery/home/ec2-user/.ssh/authorized_keys
  #Un-mounting the volume
  umount /mnt/recovery/
  
  step 6: Wait for some time as it will take time.
  
  
  step 7: Now re attach it to lost_ec2 as device path /dev/sda1
  
  
  st2p 8: Now you will be able to login to this lost_ec2 instance using new_pem.pem file