Error if there are duplicate service names

Continue to allow onboot to have duplicates as we do not run simultaneously
so that is ok (and we number them anyway), but services are run together
so we will get a runtime error if duplicated as this is the containerd/runc
id.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

cmd/moby/build.go

@@ -199,7 +199,10 @@ func build(args []string) {
 		if err != nil {
 			log.Fatalf("Invalid config: %v", err)
 		}
-		m = moby.AppendConfig(m, c)
+		m, err = moby.AppendConfig(m, c)
+		if err != nil {
+			log.Fatalf("Cannot append config files: %v", err)
+		}
 	}
 
 	if *buildDisableTrust {

src/moby/config.go

@@ -105,6 +105,18 @@ func convert(i interface{}) interface{} {
 	return i
 }
 
+func uniqueServices(m Moby) error {
+	// service names must be unique, as they run as simultaneous containers
+	names := map[string]bool{}
+	for _, s := range m.Services {
+		if names[s.Name] {
+			return fmt.Errorf("duplicate service name: %s", s.Name)
+		}
+		names[s.Name] = true
+	}
+	return nil
+}
+
 // NewConfig parses a config file
 func NewConfig(config []byte) (Moby, error) {
 	m := Moby{}
@@ -140,11 +152,15 @@ func NewConfig(config []byte) (Moby, error) {
 		return m, err
 	}
 
+	if err := uniqueServices(m); err != nil {
+		return m, err
+	}
+
 	return m, nil
 }
 
 // AppendConfig appends two configs.
-func AppendConfig(m0, m1 Moby) Moby {
+func AppendConfig(m0, m1 Moby) (Moby, error) {
 	moby := m0
 	if m1.Kernel.Image != "" {
 		moby.Kernel.Image = m1.Kernel.Image
@@ -159,7 +175,11 @@ func AppendConfig(m0, m1 Moby) Moby {
 	moby.Trust.Image = append(moby.Trust.Image, m1.Trust.Image...)
 	moby.Trust.Org = append(moby.Trust.Org, m1.Trust.Org...)
 
-	return moby
+	if err := uniqueServices(moby); err != nil {
+		return moby, err
+	}
+
+	return moby, nil
 }
 
 // NewImage validates an parses yaml or json for a Image