Docker用途

Docker在各种操作系统上作了一层Docker Engine，https://docs.docker.com/engine/docker-overview/ ，

使得开发人员可以不再关注操作系统层面的操作，比如安装一个应用，如Redis，在Mac上要用brew install redis， Ubuntu上要用apt-get ... , CentOS上要用yum install ...。

在Docker上作，我们只要面向docker，向docker hub上下载一个Redis image，这个image会生成实例Container，Container中安装着可被运行的Redis。

https://docs.docker.com/develop/develop-images/dockerfile_best-practices/

https://docs.docker.com/engine/reference/builder/

Helpful skills

docker image ls
docker image prune
docker image rm <image_name> # Remove an image

docker-compose build
docker-compose up
docker-compose ps
docker-compose down

docker build -t sometagname . # build a image from Dockerfile
docker run --publish 80:8000 --detach --name container0 sometagname # Will create a container from image sometagname.
--env-file .env 
docker ps
docker container ls -a
<tag or id, etc.>
docker container rm container_name_or_id # Remove a container
docker exec -it container_name_or_id bash # Enter a shell of a container. 'container_name' is the name of the container or can be the container id.
docker stop container_name_or_id
docker start container_name_or_id

docker system prune -a # When you build images, it will take your disk space for storing the cache. You can use this command to reclaim your space.

docker tag 8f804fe0084d harley/great-repo1:latest # 8f804fe0084d is an existing `IMAGE ID`, you run it to create a new image which REPOSITORY is `harley/great-repo1` and TAG is `latest`. In this way, you don't need to build again and again.
docker push harley/great-repo1:latest # push it to Docker hub
  • For Django user, the service named db_name in docker-compose.yml should be referred properly in DATABASES = { ‘default’: { ‘HOST’: ‘db_name’ } } settings.py. 
    $ docker-compose run db_name bash
then you can run belew command in a new container created from image 'db_name'
$ psql
  • click docker - preferences - Resources - File Sharing + can make a local folder shared for docker.
  • Change Dockerfile will cause docker image build created an new image.

Docker上示例文章重点解读

解读 https://docs.docker.com/get-started/part4/#create-a-cluster

当前我在Mac上，安装了完整的Docker，并且用Virtual Box创建了两个Linux的VM（其实是docker-machine create --driver virtualbox myvm1帮我自动创建的）。

And made myvm1 as the active machine. Then when I type docker ...., actually I was at the myvm1’s env.

E.g: docker image ls, I see nothing. Good, this means I was really in myvm1 env. When I switch to a new Terminal tab and type docker image ls, I see 4 images created at by Mac OS.

Other important articles

https://docs.docker.com/engine/docker-overview/

https://docs.docker.com/compose/rails/

Here we can see how to cache ruby gems to speed up the image building (Cut 90% time off!)

Just look at my Dockerfile to see how to make gems cached

OS

Docker’s generic base OS is Ubuntu.

遗留问题和我的解答

  • 常规应用（如Redis）的Base OS没有吗？那么运行它的操作系统是什么？配置文件如何修改？

Answer: https://github.com/docker-library/redis/blob/7be79f51e29a009fefdc218c8479d340b8c4a5e1/5.0/Dockerfile

For Redis, its base OS is Debian.

If you want a Redis running on CentOS, just search ‘docker Redis CentOS’ by Google. You’ll get https://hub.docker.com/r/centos/redis/ .

  • 如何打包项目文件，生成项目image并push到docker hub上？ Answer:

1 Choose a base OS and programming language which you want. Default base OS is Ubuntu.

2 docker build your project’s image.

3 docker push your project’s image.