For free tier users, to set the budget threshold as 0.8 (or any number under 1) prevents extra fees caused by utilizing non-trial resources.
Make sure the mail you left is the one you frequently checked, otherwise it does not make any sense.
Ports are only accessible to IPs on the whitelist because IPs acquired from computing platforms are under malicious scanning around the world, and it never stops.
Amazon Machine Image (AMI)
Some Linux distributions installed from AMI initially don't allow you to log in as a
root user. Follow prompts returned in terminal, then set the root password using