Setting a default locale
Setting a instance hostname
Generating instance ssh private keys
Adding ssh keys to a users .ssh/authorized_keys so they can log in
Setting up ephemeral mount points
Cloud-init ‘s behavior can be configured via user-data.
User-data can be given by the user at instance launch time.
This is done via the –user-data or –user-data-file argument to ec2-run-instances for example.
Check your local clients documentation for how to provide a user-data string or user-data file for usage by cloud-init on instance creation.