Jervis docker clients

These are the docker build files to create Jervis docker clients as Jenkins build slaves.

Build all operating system variants

A helpful build script is provided.

./build.sh

This will build the following containers:

• jervis-alpine:latest
• jervis-centos7:latest
• jervis-centos7-android:latest
• jervis-centos7-dnd:latest
• jervis-ubuntu1604:latest
• jervis-ubuntu1804:latest

Alternatively, to build a single variant, simply pass one or more directories as arguments to build.sh. For example, to build jervis-centos7-android you must first build the jervis-centos7 base image.

./build.sh centos7 centos7-android

Running containers

docker run is the typical method for running containers. To launch the centos7 container:

docker run -it --rm jervis-centos7 /bin/bash

Other images can be launched with similar commands unless otherwise stated.

Working with android emulators

The jervis-centos7-android image provides Android SDK tools, Android platform-tools, and Android emulator. However, it does not install machine images or set up hardware. That's left up to the developer running a build to do in their build scripts. Here's an example of starting an emulator in the background for running UI tests. For operating on most common Android phones, android-22 for ARMv7 is recommended.

docker run -it --rm jervis-centos7-android /bin/bash

From within the docker container:

yes | sdkmanager platform-tools emulator 'platforms;android-22' 'system-images;android-22;default;armeabi-v7a'
yes '' | avdmanager create avd --package 'system-images;android-22;default;armeabi-v7a' --abi armeabi-v7a --name android-phone
adb start-server
nohup emulator -avd android-phone -no-skin -no-window &

Now you're ready to run your tests.

./gradlew clean test connectedAndroidTest

Working with docker in docker

The jervis-centos7-dnd image is provided for docker in docker operations. Running the container with --privileged is required, however Docker CE has done a lot of work to make sure --privileged is as safe as possible to run docker in docker. The reason why --privileged is required is that docker needs write access to /sys/fs/cgroup and other kernel APIs only available in --privileged mode.

See security writeups:

• Docker security.
• Docker run capabilies when --privileged option is used.

Starting a docker container which runs docker in docker.

docker volume create docker-data
docker run -it --rm --privileged -v docker-data:/var/lib/docker jervis-centos7-dnd /bin/bash

All following commands occur within the docker container.

# start docker daemon with debug logging
sudo -i nohup dockerd -D &
# writes docker daemon logs to /root/nohup.out
docker pull centos:7
# run a docker container inside of the docker container
docker run -it --rm centos:7 /bin/bash

Things to note:

• docker daemon requires write access to a volume mounted on /var/lib/docker. We did that by using docker volumes with -v docker-data:/var/lib/docker.
• Do not use the docker-data volume with more than one docker in docker container. If you need to launch a second docker in docker container, then create and mount a volume with a different name. Accessing /var/lib/docker with multiple docker daemons will cause data corruption.