the snippets are not variables but templates themselves, which are usually used in other templates.
For example the remote_execution_ssh_keys-snippet is not only used in the kickstart default finish, but also in kickstart default, preseed finish and autoyast.
In this case the ssh-keys for remote execution are read from all smart proxies and added to the authorized_keys during provisioning. You could also create a special ssh-user with sudo-priviledges using this snippet.
If you have already provisioned machines and you also use Katello, you could use the bootstrap.py-script to register them and there is also an option to add the ssh-keys for remote execution.
Another way would be a configuration management tool such as puppet to manage ssh-keys on the machine.
If you plan to adapt templates, i recommend to clone an existing one and edit it then. If you unlock and edit community templates your changes might be overwritten during upgrades.
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