feat(hostname): Set hostname from cloud-config

cloudinit/cloud_config.go

@@ -17,6 +17,7 @@ type CloudConfig struct {
 		Units []Unit
 	}
 	Write_Files []WriteFile
+	Hostname    string
 }
 
 func NewCloudConfig(contents []byte) (*CloudConfig, error) {
@@ -38,6 +39,13 @@ func (cc CloudConfig) String() string {
 }
 
 func ApplyCloudConfig(cfg CloudConfig, sshKeyName string) error {
+	if cfg.Hostname != "" {
+		if err := SetHostname(cfg.Hostname); err != nil {
+			return err
+		}
+		log.Printf("Set hostname to %s", cfg.Hostname)
+	}
+
 	if len(cfg.SSH_Authorized_Keys) > 0 {
 		err := AuthorizeSSHKeys(sshKeyName, cfg.SSH_Authorized_Keys)
 		if err == nil {

cloudinit/cloud_config_test.go

@@ -28,6 +28,10 @@ func TestCloudConfigEmpty(t *testing.T) {
 	if len(cfg.Write_Files) != 0 {
 		t.Error("Expected zero Write_Files")
 	}
+
+	if cfg.Hostname != "" {
+		t.Errorf("Expected hostname to be empty, got '%s'", cfg.Hostname)
+	}
 }
 
 // Assert that the parsing of a cloud config file "generally works"
@@ -61,6 +65,7 @@ write_files:
     path: /etc/dogepack.conf
     permissions: '0644'
     owner: root:dogepack
+hostname: trontastic
 `)
 	cfg, err := NewCloudConfig(contents)
 	if err != nil {
@@ -129,6 +134,9 @@ Address=10.209.171.177/19
 		}
 	}
 
+	if cfg.Hostname != "trontastic" {
+		t.Errorf("Failed to parse hostname")
+	}
 }
 
 // Assert that our interface conversion doesn't panic

cloudinit/systemd.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"os/exec"
 	"path"
 	"path/filepath"
 	"strings"
@@ -150,3 +151,7 @@ func ExecuteScript(scriptPath string) (string, error) {
 	_, err = conn.StartTransientUnit(name, "replace", props...)
 	return name, err
 }
+
+func SetHostname(hostname string) error {
+	return exec.Command("hostnamectl", "set-hostname", hostname).Run()
+}