commands/operator-sdk/cmd/build.go: prefer buildah over docker

buildah is safer than docker because it can run containers without sudo.
Fall back to docker if buildah not installed

Author: estroz

commands/operator-sdk/cmd/build.go

@@ -132,6 +132,11 @@ func verifyTestManifest(image string) {
 	}
 }
 
+func isBuildahAvail() bool {
+	_, err := exec.LookPath("buildah")
+	return err == nil
+}
+
 func buildFunc(cmd *cobra.Command, args []string) {
 	if len(args) != 1 {
 		log.Fatalf("build command needs exactly 1 argument")
@@ -162,8 +167,19 @@ func buildFunc(cmd *cobra.Command, args []string) {
 	if enableTests {
 		baseImageName += "-intermediate"
 	}
-	dbcmd := exec.Command("docker", "build", ".", "-f", "build/Dockerfile", "-t", baseImageName)
-	o, err := dbcmd.CombinedOutput()
+
+	var buildCmd *exec.Cmd
+	if isBuildahAvail() {
+		buildCmd = exec.Command("buildah", "bud",
+			"-f", filepath.Join(scaffold.BuildDir, scaffold.DockerfileFile),
+			"--isolation", "rootless",
+			"-t", baseImageName)
+	} else {
+		buildCmd = exec.Command("docker", "build", ".",
+			"-f", filepath.Join(scaffold.BuildDir, scaffold.DockerfileFile),
+			"-t", baseImageName)
+	}
+	o, err := buildCmd.CombinedOutput()
 	if err != nil {
 		if enableTests {
 			log.Fatalf("failed to build intermediate image for %s image: %v (%s)", image, err, string(o))
@@ -205,8 +221,22 @@ func buildFunc(cmd *cobra.Command, args []string) {
 			}
 		}
 
-		testDbcmd := exec.Command("docker", "build", ".", "-f", testDockerfile, "-t", image, "--build-arg", "NAMESPACEDMAN="+namespacedManBuild, "--build-arg", "BASEIMAGE="+baseImageName)
-		o, err = testDbcmd.CombinedOutput()
+		var testBuildCmd *exec.Cmd
+		if isBuildahAvail() {
+			testBuildCmd = exec.Command("buildah", "bud",
+				"-f", testDockerfile,
+				"--isolation", "rootless",
+				"-t", image,
+				"--build-arg", "NAMESPACEDMAN="+namespacedManBuild,
+				"--build-arg", "BASEIMAGE="+baseImageName)
+		} else {
+			testBuildCmd = exec.Command("docker", "build", ".",
+				"-f", testDockerfile,
+				"-t", image,
+				"--build-arg", "NAMESPACEDMAN="+namespacedManBuild,
+				"--build-arg", "BASEIMAGE="+baseImageName)
+		}
+		o, err = testBuildCmd.CombinedOutput()
 		if err != nil {
 			log.Fatalf("failed to output build image %s: %v (%s)", image, err, string(o))
 		}