This note is about the problems that I met while using Docker.

What is Docker

Definition^[1]

Build, Ship, and Run Any App, Anywhere

Components

• Docker Client
• Docker Daemon
• Docker Image
• Docker Registry
• Docker Container

Architecture

Difference between docker containers and virtual machines

Docker Containers	Virtual Machines

Core Tech^[2]

• Linux Namespace(ns)

  • pid namespace
  • net namespace
  • ipc namespace
  • mnt namespace
  • uts namespace
  • user namespace

• Contral Groups(cgroups)

  • blkio
  • cpu
  • cpuacct
  • cpuset
  • devices
  • freezer
  • memory
  • net_cls
  • ns

• AUFS(AnotherUnionFS)

• Security

  • Secured by kernel namespaces and cgroups.
  • Secured by Docker Deamon APIs.
  • Secured by Linux’s solution such as AppArmor, SELinux.

Requirement

See official guide.

Install

See official guide.

Configuration

Use Dockerfile to build the image

# In the host
# Dockerfile is in current folder
$ docker build . -t image_name

Often used commands

• ADD
• ENV
• EXPOSE
• FROM
• RUN
• CMD

Set Java

Use Dockerfile to build the image.

# Set Java environment
ENV JAVA_HOME /home/java/jre/
ENV CLASSPATH .:/home/java/jre/lib
ENV PATH /home/java/jre/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

Set Locale

Configure the locales in the host.

Use Dockerfile to build the image.

# Set locales
RUN locale-gen en_US en_US.UTF-8
RUN locale-gen zh_CN zh_CN.UTF-8
RUN locale-gen nb_NO nb_NO.UTF-8
ENV LANG en_US.utf8

Set Port

Use Dockerfile to build the image.

# Expose the port to the public
EXPOSE 80

MySQL

Install in the host.

Vsftpd

Install in the host.

Often used commands

RUN

This command creates a container from a docker image.

$ docker run -t -i -p 80:80 -p 443:443 -p 8092:8092 -v /home:/home --name container_name --hostname web username/image

-v Better use absolute path.

START

This command starts a container which is stopped.

$ docker start container_id/container_name

STOP

This command stops a container which is running.

$ docker stop container_id/container_name

ATTACH

This command enters into a started container.

$ docker attach container_id/container_name

While you are in a container, you cannot leave it with ctrl + c. This will stop the container. Use ctrl + p + q instead.

Use attach to enter it again.

PS

This command displays containers.

# Display running containers
$ docker ps

# Display all containers
$ docker ps -a

IMAGES

This command displays images.

$ docker images

RM

This command removes a container.

$ docker rm container_id/container_name

The container has to be stopped.

RMI

This command removes an image

$ docker rmi image_name

COMMIT

This command commits changes in a container to a image.

$ docker commit container_name image_name

PUSH

This command pushes local image to a repository.

$ docker push username/repo_name:tag

PULL

This command pulls image from a repository.

$ docker pull username/repo_name

SAVE

This command saves image to a local file.

$ docker save -o file_name.tar image_name:tag_name1 image_name:tag_name2

LOAD

This command loads image from a local file.

$ docker load --input file_name.tar

REMOVE UNUSED IMAGES

This command removes all unused images.

$ docker image prune -a

DockerHub

Using different tags to store different versions.

Reference

1. https://www.docker.com/

2. http://www.infoq.com/cn/articles/docker-core-technology-preview

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