Add dockerExecCommand setting

src/main/scala/com/typesafe/sbt/packager/docker/DockerPlugin.scala

@@ -82,13 +82,14 @@ object DockerPlugin extends AutoPlugin {
     dockerUpdateLatest := false,
     dockerEntrypoint := Seq("bin/%s" format executableScriptName.value),
     dockerCmd := Seq(),
+    dockerExecCommand := Seq("docker"),
     dockerBuildOptions := Seq("--force-rm") ++ Seq("-t", dockerAlias.value.versioned) ++ (
       if (dockerUpdateLatest.value)
         Seq("-t", dockerAlias.value.latest)
       else
         Seq()
     ),
-    dockerBuildCommand := Seq("docker", "build") ++ dockerBuildOptions.value ++ Seq("."),
+    dockerBuildCommand := dockerExecCommand.value ++ Seq("build") ++ dockerBuildOptions.value ++ Seq("."),
     dockerCommands := {
       val dockerBaseDirectory = (defaultLinuxInstallLocation in Docker).value
       val user = (daemonUser in Docker).value
@@ -122,11 +123,11 @@ object DockerPlugin extends AutoPlugin {
           publishLocalDocker(context, buildCommand, s.log)
           s.log.info(s"Built image $alias")
       },
-      publish <<= (publishLocal, dockerAlias, dockerUpdateLatest, streams) map {
-        (_, alias, updateLatest, s) =>
-          publishDocker(alias.versioned, s.log)
+      publish <<= (publishLocal, dockerAlias, dockerUpdateLatest, dockerExecCommand, streams) map {
+        (_, alias, updateLatest, dockerExecCommand, s) =>
+          publishDocker(dockerExecCommand ,alias.versioned, s.log)
           if (updateLatest) {
-            publishDocker(alias.latest, s.log)
+            publishDocker(dockerExecCommand, alias.latest, s.log)
           }
       },
       sourceDirectory := sourceDirectory.value / "docker",
@@ -310,7 +311,7 @@ object DockerPlugin extends AutoPlugin {
       throw new RuntimeException("Nonzero exit value: " + ret)
   }
 
-  def publishDocker(tag: String, log: Logger): Unit = {
+  def publishDocker(execCommand: Seq[String], tag: String, log: Logger): Unit = {
     val loginRequired = new AtomicBoolean(false)
 
     def publishLogger(log: Logger) =

src/main/scala/com/typesafe/sbt/packager/docker/Keys.scala

@@ -27,6 +27,7 @@ trait DockerKeys {
     "dockerCmd",
     "Docker CMD. Used together with dockerEntrypoint. Arguments passed in exec form"
   )
+  val dockerExecCommand = SettingKey[Seq[String]]("dockerExecCommand", "The shell command used to exec Docker")
   val dockerBuildOptions = SettingKey[Seq[String]]("dockerBuildOptions", "Options used for the Docker build")
   val dockerBuildCommand = SettingKey[Seq[String]]("dockerBuildCommand", "Command for building the Docker image")
 

src/sbt-test/docker/simple-docker/build.sbt

@@ -1,6 +1,6 @@
 enablePlugins(JavaAppPackaging)
 
-name := "docker-test"
+name := "simple-docker"
 
 version := "0.1.0"
 

src/sbt-test/docker/simple-docker/test

@@ -1,3 +1,3 @@
 # Generate the Docker image locally
 > docker:publishLocal
-$ exec bash -c 'docker run docker-test:0.1.0 | grep -q "Hello world"'
+$ exec bash -c 'docker run simple-docker:0.1.0 | grep -q "Hello world"'

src/sbt-test/docker/simple-sudo-docker/build.sbt

@@ -0,0 +1,9 @@
+enablePlugins(JavaAppPackaging)
+
+name := "simple-sudo-docker"
+
+version := "0.1.0"
+
+maintainer := "G. Richard Bellamy <[email protected]>"
+
+dockerExecCommand := Seq("sudo", "docker")

src/sbt-test/docker/simple-sudo-docker/project/plugins.sbt

@@ -0,0 +1 @@
+addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % sys.props("project.version"))

src/sbt-test/docker/simple-sudo-docker/src/main/scala/Main.scala

@@ -0,0 +1,3 @@
+object Main extends App {
+  println("Hello world")
+}

src/sbt-test/docker/simple-sudo-docker/test

@@ -0,0 +1,3 @@
+# Generate the Docker image locally
+> docker:publishLocal
+$ exec bash -c 'docker run simple-sudo-docker:0.1.0 | grep -q "Hello world"'

src/sphinx/formats/docker.rst

@@ -122,16 +122,20 @@ Publishing Settings
 
   ``dockerAlias``
     The alias to be used for tagging the resulting image of the Docker build.
-    The type of the setting key is ``DockerAlias`.
+    The type of the setting key is ``DockerAlias``.
     Defaults to ``[dockerRepository/][name]:[version]``.
 
   ``dockerBuildOptions``
     Overrides the default Docker build options.
     Defaults to ``Seq("--force-rm", "-t", "[dockerAlias]")``. This default is expanded if ``dockerUpdateLatest`` is set to true.
 
+  ``dockerExecCommand``
+    Overrides the default Docker exec command.
+    Defaults to ``Seq("docker")``
+
   ``dockerBuildCommand``
-    Overrides the default Docker build command.
-    Defaults to ``Seq("docker", "build", "[dockerBuildOptions]", ".")``.
+    Overrides the default Docker build command. The reason for this is that many systems restrict docker execution to root, and while the accepted guidance is to alias the docker command ``alias docker='/usr/bin/docker'``, neither Java nor Scala support passing aliases to sub-processes, and most build systems run builds using a non-login, non-interactive shell, which also have limited support for aliases, which means that the only viable option is to use ``sudo docker`` directly.
+    Defaults to ``Seq("[dockerExecCommand]", "build", "[dockerBuildOptions]", ".")``.
 
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