feat(config-drive): Add support for reading user-data from config-drive

The -config-drive flag tells cloudinit to read the user-data from
within the config-drive (./openstack/latest/user-data).

coreos-cloudinit.go

@@ -28,6 +28,9 @@ func main() {
 	var file string
 	flag.StringVar(&file, "from-file", "", "Read user-data from provided file")
 
+	var configdrive string
+	flag.StringVar(&configdrive, "from-configdrive", "", "Read user-data from provided cloud-drive directory")
+
 	var url string
 	flag.StringVar(&url, "from-url", "", "Download user-data from provided url")
 
@@ -52,10 +55,12 @@ func main() {
 		ds = datasource.NewLocalFile(file)
 	} else if url != "" {
 		ds = datasource.NewMetadataService(url)
+	} else if configdrive != "" {
+		ds = datasource.NewConfigDrive(configdrive)
 	} else if useProcCmdline {
 		ds = datasource.NewProcCmdline()
 	} else {
-		fmt.Println("Provide one of --from-file, --from-url or --from-proc-cmdline")
+		fmt.Println("Provide one of --from-file, --from-configdrive, --from-url or --from-proc-cmdline")
 		os.Exit(1)
 	}
 

datasource/configdrive.go

@@ -0,0 +1,27 @@
+package datasource
+
+import (
+	"io/ioutil"
+	"os"
+	"path"
+)
+
+type configDrive struct {
+	path string
+}
+
+func NewConfigDrive(path string) *configDrive {
+	return &configDrive{path}
+}
+
+func (self *configDrive) Fetch() ([]byte, error) {
+	data, err := ioutil.ReadFile(path.Join(self.path, "openstack", "latest", "user_data"))
+	if os.IsNotExist(err) {
+		err = nil
+	}
+	return data, err
+}
+
+func (self *configDrive) Type() string {
+	return "cloud-drive"
+}