Start play framework app from dockerfile - sbt

Question

I want to start a play framework 2 application in a Dockerfile.
Let us assume my play project rests in the /myapp directory in ubuntu.
When I start it manually, I would just say:
cd /myapp
sbt run
How can I run sbt run on it from the CMD command of the Dockerfile?
Running sbt run has to be from within the /myapp directory. How do I tell the CMD command that sbt run should be run from that directory?

Answer 1

Take a closer look at the new experimental docker feature
for the sbt-native-packager.
You should be able to build a docker container from your play application with a few simple steps.
Adding a maintainer and the exposed ports
import NativePackagerKeys._ // with auto plugins this won't be necessary soon
name := "play-2.3"
version := "1.0-SNAPSHOT"
lazy val root = (project in file(".")).enablePlugins(PlayScala)
scalaVersion := "2.11.1"
libraryDependencies ++= Seq(
jdbc,
anorm,
cache,
ws
)
// setting a maintainer which is used for all packaging types
maintainer := "Nepomuk Seiler"
// exposing the play ports
dockerExposedPorts in Docker := Seq(9000, 9443)
and then run
sbt docker:publishLocal
docker run -p 9000:9000 play-2-3:1.0-SNAPSHOT
Update - 1.x version
With sbt-native-packager 1.x ( and so with play 2.4.x ) docker is enabled by default ( because play enables the JavaServerAppPackaging plugin ).
If you don't have a play application then enable docker with
enablePlugins(JavaAppPackagingPlugin)
maintainer := "Nepomuk Seiler"
// note that the Docker scope is gone!
dockerExposedPorts := Seq(9000, 9443)

Answer 2

You can just connect both statements:
FROM ubuntu
... more Dockerfile commands...
CMD cd /myapp && sbt run
You could also use the WORKDIR command of Dockerfiles (see http://docs.docker.io/reference/builder/#workdir) to set the working directory for your CMD command. But I never used this for myself (with no specific reason...):
FROM ubuntu
... more Dockerfile commands...
WORKDIR /myapp
CMD sbt run