Merge pull request #2438 from dgageot/generic-doc

Improve generic driver documentation

docs/drivers/generic.md

@@ -16,10 +16,16 @@ This is useful if you are using a provider that Machine does not support
 directly or if you would like to import an existing host to allow Docker
 Machine to manage.
 
+The driver will perform a list of tasks on create:
+
+-   If docker is not running on the host, it will be installed automatically.
+-   It will generate certificates to secure the docker daemon
+-   The docker daemon will be restarted, thus all running containers will be stopped.
+
 Options:
 
 -   `--generic-ip-address`: **required** IP Address of host.
--   `--generic-ssh-key`: **required** Path to the SSH user private key.
+-   `--generic-ssh-key`: Path to the SSH user private key.
 -   `--generic-ssh-user`: SSH username used to connect.
 -   `--generic-ssh-port`: Port to use for SSH.
 
@@ -30,6 +36,6 @@ Environment variables and default values:
 | CLI option                 | Environment variable | Default             |
 | -------------------------- | -------------------- | ------------------- |
 | **`--generic-ip-address`** | `GENERIC_IP_ADDRESS` | -                   |
-| **`--generic-ssh-key`**    | `GENERIC_SSH_KEY`    | `$HOME/.ssh/id_rsa` |
+| `--generic-ssh-key`        | `GENERIC_SSH_KEY`    | `$HOME/.ssh/id_rsa` |
 | `--generic-ssh-user`       | `GENERIC_SSH_USER`   | `root`              |
 | `--generic-ssh-port`       | `GENERIC_SSH_PORT`   | `22`                |