diff --git a/.gitignore b/.gitignore
index 6e17878..2e71f2e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@ bin/
 dist/
 images
 wstation
+/d2vm
diff --git a/Dockerfile b/Dockerfile
index 2f8f39c..4119a84 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -25,7 +25,7 @@ COPY . .
 
 RUN make .build
 
-FROM ubuntu
+FROM ubuntu:20.04
 
 RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get -y install --no-install-recommends \
diff --git a/Makefile b/Makefile
index e84eab0..694c584 100644
--- a/Makefile
+++ b/Makefile
@@ -70,6 +70,8 @@ check-fmt:
 vet:
 	@go list ./...|grep -v scratch|GOOS=linux xargs go vet
 
+build-dev: docker-build .build
+
 .build:
 	@go generate ./...
 	@go build -o d2vm -ldflags "-s -w -X '$(MODULE).Version=$(VERSION)' -X '$(MODULE).BuildDate=$(shell date)'" ./cmd/d2vm
diff --git a/cmd/d2vm/run/sparsecat-linux-amd64 b/cmd/d2vm/run/sparsecat-linux-amd64
index bdf2fee..90fdeff 100755
Binary files a/cmd/d2vm/run/sparsecat-linux-amd64 and b/cmd/d2vm/run/sparsecat-linux-amd64 differ
diff --git a/dockerfile.go b/dockerfile.go
index e0d281b..ac59253 100644
--- a/dockerfile.go
+++ b/dockerfile.go
@@ -50,6 +50,15 @@ const (
 	NetworkManagerNetplan   NetworkManager = "netplan"
 )
 
+func (n NetworkManager) Validate() error {
+	switch n {
+	case NetworkManagerNone, NetworkManagerIfupdown2, NetworkManagerNetplan:
+		return nil
+	default:
+		return fmt.Errorf("unsupported network manager: %s", n)
+	}
+}
+
 type Dockerfile struct {
 	Image          string
 	Password       string
@@ -78,14 +87,26 @@ func NewDockerfile(release OSRelease, img, password string, networkManager Netwo
 	case ReleaseAlpine:
 		d.tmpl = alpineDockerfileTemplate
 		net = NetworkManagerIfupdown2
+		if networkManager == NetworkManagerNetplan {
+			return d, fmt.Errorf("netplan is not supported on alpine")
+		}
 	case ReleaseCentOS:
 		d.tmpl = centOSDockerfileTemplate
+		net = NetworkManagerNone
+		if networkManager != "" && networkManager != NetworkManagerNone {
+			return Dockerfile{}, fmt.Errorf("network manager is not supported on centos")
+		}
 	default:
 		return Dockerfile{}, fmt.Errorf("unsupported distribution: %s", release.ID)
 	}
 	if d.NetworkManager == "" {
-		logrus.Warnf("no network manager specified, using distribution defaults: %s", net)
+		if release.ID != ReleaseCentOS {
+			logrus.Warnf("no network manager specified, using distribution defaults: %s", net)
+		}
 		d.NetworkManager = net
 	}
+	if err := d.NetworkManager.Validate(); err != nil {
+		return Dockerfile{}, err
+	}
 	return d, nil
 }
diff --git a/pkg/docker/docker.go b/pkg/docker/docker.go
index 5825ef7..7b6e3fe 100644
--- a/pkg/docker/docker.go
+++ b/pkg/docker/docker.go
@@ -102,6 +102,9 @@ func RunD2VM(ctx context.Context, image, version, cmd string, args ...string) er
 	if err != nil {
 		return err
 	}
+	if image == "" {
+		image = "linkacloud/d2vm"
+	}
 	if version == "" {
 		version = "latest"
 	}