Creating an Amazon EC2 instance

Remove SSH Host Key Pairs:

If you plan to share an AMI derived from a public AMI, remove the existing SSH host key pairs located in /etc/ssh. This forces SSH to generate new unique SSH key pairs when someone launches an instance using your AMI, improving security and reducing the likelihood of "man-in-the-middle" attacks.

You can securely remove all of these files with the following command.

# shred -u /etc/ssh/*_key /etc/ssh/*_key.pub

Restart the sshd service:

# systemctl restart sshd.service

Switch to root account:

# sudo su -

Reference:

http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/building-shared-amis.html