Docker

Prerequisites

Installation

The installation of docker is out of scope of this tutorial, please refer the official document for the docker installation.

Rules

Create the Images (Dockfiles) for development (mount project as volume) and deployment (integrate project)
Keep persistent data separating from docker container
Connect the docker containers instead of putting everything in the same container

Operations

Run

Run docker container in interactive mode with option `-t` and `-i`

    > docker run -t -i ubuntu:14.04.2 /bin/bash

Run docker container with volume mounted by option `-v`

    > docker run -t -i -v hostDir1:containerDir1 \
                       -v hostDir2:containerDir2 \
                       ubuntu:14.04.2 /bin/bash

Set volume as privileged, Ex. active host usb

    > docker run -t -i --privileged -v /dev/bus/usb:/dev/bus/usb \
                                    ubuntu /bin/bash

Run docker container with ports opened by option `-p` (TODO)

    > docker run -t -i ubuntu:14.04.2 /bin/bash

Run docker container with all ports in container mapped to host `-P`

    > docker run -d -P myWebServer python app.py

-d runs docker container in background (daemon)

Attach a background running container

Get access:

    > docker attach containerID

Exit without halt Ctrl+p and Ctrl+q

Stop the running container

    > docker stop containerID

Manage Image

Commit the change in container to image

    > docker ps # verify the containerID
    > docker commit -m "some mesg" containerID imageName:tag

Export/Import Image to `tar` file

Export the image

Import the image

Dockerfile

! For Ubuntu/Debian, it is better to create a base system image with upgraded package apt-get update && apt-get upgrade -y

Dockerfile example

# DOCKER-VERSION 1.6.0
# Erlang docker image

FROM ubuntubase:v1
MAINTAINER Jun HU <[email protected]>


# add the erlang repo and key
RUN echo "deb http://packages.erlang-solutions.com/ubuntu trusty contrib" >> /etc/apt/sources.list
RUN DEBIAN_FRONTEND=noninteractive apt-get install wget -y
RUN wget http://packages.erlang-solutions.com/ubuntu/erlang_solutions.asc
RUN apt-key add erlang_solutions.asc

RUN apt-get update
RUN DEBIAN_FRONTEND=noninteractive apt-get install -y \
    erlang \
    rebar

Build image from Dockerfile

    > docker build -t "MyDockerImageName:tag" -f MyDockerfile # by default, the file name is Dockerfile

Management

Pull the images from Docker public repository

Build private local repository

Ref

Ref1

References

Docker without docker slide
Docker on arm processor tutorial
Docker image for ubuntu-core on armhf

Definitions

Container

Image

Docker images are the basis of containers.

Data volume

A data volume is a specially-designated directory within one or more containers that bypasses the Union File System. Data volumes provide several useful features for persistent or shared data:

Volumes are initialized when a container is created. If the container's base image contains data at the specified mount point, that data is copied into the new volume.
Data volumes can be shared and reused among containers.
Changes to a data volume are made directly.
Changes to a data volume will not be included when you update an image.
Data volumes persist even if the container itself is deleted.

Data volumes are designed to persist data, independent of the container's life cycle. Docker therefore never automatically delete volumes when you remove a container, nor will it "garbage collect" volumes that are no longer referenced by a container.

Preparation

The official tutorial can be found here

Install docker

Create docker group

    > sudo usermod -aG docker yourusername

Adjust memory and swap accounting

Set GRUB_CMDLINE_LINUX in /etc/default/grub

   GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1"

Update Grub and reboot

    > sudo update-grub && sudo reboot

Upgrade and reboot docker

    > wget -N https://get.docker.com/ | sh
    > sudo restart network-manager $ sudo restart docker

perigee/Docker.md