exoscale: add ability to specify customer user data for cloud-init

CoreOS user are likely to want this capacity as it enables the
configuration of the etcd cluster. Moreover, we remove some of the
default options as they are not supported in CoreOS and are useless on
Debian/Ubuntu:

 - Resizing of rootfs is already done on all images by default.
 - Docker Machine will set the hostname as part of the provisioning.

Signed-off-by: Vincent Bernat <Vincent.Bernat@exoscale.ch>

docs/drivers/exoscale.md

@@ -27,6 +27,7 @@ Options:
 -   `--exoscale-security-group`: Security group. It will be created if it doesn't exist.
 -   `--exoscale-availability-zone`: Exoscale availability zone.
 -   `--exoscale-ssh-user`: SSH username, which must match the default SSH user for the used image.
+-   `--exoscale-userdata`: Path to file containing user data for cloud-init.
 
 If a custom security group is provided, you need to ensure that you allow TCP ports 22 and 2376 in an ingress rule. Moreover, if you want to use Swarm, also add TCP port 3376.
 
@@ -43,3 +44,4 @@ Environment variables and default values:
 | `--exoscale-security-group`     | `EXOSCALE_SECURITY_GROUP`    | `docker-machine`                  |
 | `--exoscale-availability-zone`  | `EXOSCALE_AVAILABILITY_ZONE` | `ch-gva-2`                        |
 | `--exoscale-ssh-user`           | `EXOSCALE_SSH_USER`          | `ubuntu`                          |
+| `--exoscale-userdata`           | `EXOSCALE_USERDATA`          | -                                 |

drivers/exoscale/exoscale.go

@@ -1,12 +1,11 @@
 package exoscale
 
 import (
-	"bytes"
 	"fmt"
 	"io/ioutil"
 	"net"
+	"os"
 	"strings"
-	"text/template"
 	"time"
 
 	"github.com/docker/machine/libmachine/drivers"
@@ -29,6 +28,7 @@ type Driver struct {
 	AvailabilityZone string
 	KeyPair          string
 	PublicKey        string
+	UserDataFile     string
 	ID               string `json:"Id"`
 }
 
@@ -95,6 +95,11 @@ func (d *Driver) GetCreateFlags() []mcnflag.Flag {
 			Value:  defaultSSHUser,
 			Usage:  "Set the name of the ssh user",
 		},
+		mcnflag.StringFlag{
+			EnvVar: "EXOSCALE_USERDATA",
+			Name:   "exoscale-userdata",
+			Usage:  "path to file with cloud-init user-data",
+		},
 	}
 }
 
@@ -142,6 +147,7 @@ func (d *Driver) SetConfigFromFlags(flags drivers.DriverOptions) error {
 	d.SecurityGroup = strings.Join(securityGroups, ",")
 	d.AvailabilityZone = flags.String("exoscale-availability-zone")
 	d.SSHUser = flags.String("exoscale-ssh-user")
+	d.UserDataFile = flags.String("exoscale-userdata")
 	d.SetSwarmConfigFromFlags(flags)
 
 	if d.URL == "" {
@@ -154,6 +160,16 @@ func (d *Driver) SetConfigFromFlags(flags drivers.DriverOptions) error {
 	return nil
 }
 
+func (d *Driver) PreCreateCheck() error {
+	if d.UserDataFile != "" {
+		if _, err := os.Stat(d.UserDataFile); os.IsNotExist(err) {
+			return fmt.Errorf("user-data file %s could not be found", d.UserDataFile)
+		}
+	}
+
+	return nil
+}
+
 func (d *Driver) GetURL() (string, error) {
 	if err := drivers.MustBeRunning(d); err != nil {
 		return "", err
@@ -238,6 +254,11 @@ func (d *Driver) createDefaultSecurityGroup(client *egoscale.Client, group strin
 }
 
 func (d *Driver) Create() error {
+	userdata, err := d.getCloudInit()
+	if err != nil {
+		return err
+	}
+
 	log.Infof("Querying exoscale for the requested parameters...")
 	client := egoscale.NewClient(d.URL, d.APIKey, d.APISecretKey)
 	topology, err := client.GetTopology()
@@ -303,11 +324,6 @@ func (d *Driver) Create() error {
 	d.KeyPair = keypairName
 
 	log.Infof("Spawn exoscale host...")
-
-	userdata, err := d.getCloudInit()
-	if err != nil {
-		return err
-	}
 	log.Debugf("Using the following cloud-init file:")
 	log.Debugf("%s", userdata)
 
@@ -434,20 +450,15 @@ func (d *Driver) waitForVM(client *egoscale.Client, jobid string) (*egoscale.Dep
 // Build a cloud-init user data string that will install and run
 // docker.
 func (d *Driver) getCloudInit() (string, error) {
-	const tpl = `#cloud-config
-manage_etc_hosts: true
-fqdn: {{ .MachineName }}
-resize_rootfs: true
-`
-	var buffer bytes.Buffer
-
-	tmpl, err := template.New("cloud-init").Parse(tpl)
-	if err != nil {
-		return "", err
-	}
-	err = tmpl.Execute(&buffer, d)
-	if err != nil {
-		return "", err
+	if d.UserDataFile != "" {
+		buf, err := ioutil.ReadFile(d.UserDataFile)
+		if err != nil {
+			return "", err
+		}
+		return string(buf), nil
 	}
-	return buffer.String(), nil
+
+	return `#cloud-config
+manage_etc_hosts: true
+`, nil
 }