Set hostname prior to running DHCP

https://github.com/rancher/os/issues/627

cmd/cloudinit/cloudinit.go

@@ -168,17 +168,26 @@ func fetchUserData() ([]byte, datasource.Metadata, error) {
 	return userDataBytes, metadata, nil
 }
 
+func SetHostname(cc *rancherConfig.CloudConfig) error {
+	if cc.Hostname != "" {
+		//set hostname
+		if err := hostname.SetHostname(cc.Hostname); err != nil {
+			log.WithFields(log.Fields{"err": err, "hostname": cc.Hostname}).Error("Error setting hostname")
+			return err
+		}
+	}
+
+	return nil
+}
+
 func executeCloudConfig() error {
 	cc, err := rancherConfig.LoadConfig()
 	if err != nil {
 		return err
 	}
 
-	if cc.Hostname != "" {
+	if err := SetHostname(cc); err != nil {
-		//set hostname
+		return err
-		if err := hostname.SetHostname(cc.Hostname); err != nil {
-			log.WithFields(log.Fields{"err": err, "hostname": cc.Hostname}).Error("Error setting hostname")
-		}
 	}
 
 	if len(cc.SSHAuthorizedKeys) > 0 {

cmd/network/network.go

@@ -7,6 +7,7 @@ import (
 	log "github.com/Sirupsen/logrus"
 
 	"github.com/rancher/netconf"
+	"github.com/rancher/os/cmd/cloudinit"
 	"github.com/rancher/os/config"
 )
 
@@ -20,6 +21,8 @@ func Main() {
 	if err != nil {
 		log.Fatal(err)
 	}
+	// Purposely ignore error
+	cloudinit.SetHostname(cfg)
 	if err := netconf.ApplyNetworkConfigs(&cfg.Rancher.Network); err != nil {
 		log.Fatal(err)
 	}