docker version: 1.10.1
Installing docker on CentOS 7
1. Make sure your existing yum packages are up-to-date
sudo yum update
2. Add the yum repo
vim /etc/yum.repos.d/docker.repo
[dockerrepo]
name=Docker Repository
baseurl=https://yum.dockerproject.org/repo/main/centos/$releasever/
enabled=1
gpgcheck=1
gpgkey=https://yum.dockerproject.org/gpg
3. Install the Docker package
yum -y install docker-engine
4. Start the Docker daemon
systemctl start docker.service
5. Start the docker daemon at boot
systemctl enable docker.service
6. Verify docker is installed correctly by running a test image in a container.
docker run hello-world
docker info
Container
Running an interactive shell
docker run -i -t --name first_container centos:6 /bin/bash
The -i flag starts an interactive container. The -t flag creates a pseudo-TTY that attaches stdin and stdout.
If docker can't find the image on our local Docker host, it will reach out to the Docker Hub registry run by Docker, Inc., and look for it there. Once Docker had found the image, it downloaded the image and stored it on the local host.
Working with our first container
# Checking the container's hostname
root@f7cbdac22a02:/# hostname
# Checking the container's /etc/hosts
root@f7cbdac22a02:/# cat /etc/hosts
# Installing vim
root@f7cbdac22a02:/# yum install -y vim
# exit
root@f7cbdac22a02:/# exit
The container only runs for as long as the command we specified, /bin/bash, is running.Once we exited the container, that command ended, and the container was stopped.
To detach the tty without exiting the shell, use the escape sequence Ctrl-p + Ctrl-q
List containers
docker ps -a
-a Show all containers. Only running containers are shown by default.
Starting a stopped container
# by name
docker start first_container
# by ID
docker start f7cbdac22a02
Attaching to a container
docker attach first_container
You might need to hit Enter to bring up the prompt
Creating detached container
# Starting a long-running worker process
# run the container in the background
docker run -d --name daemon_dave ubuntu /bin/sh -c "while true; do echo Hello world; sleep 1; done"
Fetching the logs of our detached container
docker logs daemon_dave
Opening a shell to your running container
docker exec -it daemon_dave bash
Inspecting the container's processes
docker top daemon_dave
Finding out more about our container
docker inspect daemon_dave
Stopping a detached container
docker stop daemon_dave
Deleting a container
docker rm daemon_dave
Deleting all containers
docker rm `docker ps -a -q`
Image
Download a pre-built image
# Download an ubuntu image
docker pull ubuntu
This will find the ubuntu image by name on Docker Hub and download it from Docker Hub to a local image cache.
Listing Docker images
docker images
local images live on our local Docker host in the /var/lib/docker directory.
Searching for images
docker search centos
Updating and committing an image
To update an image you first need to create a container from the image you’d like to update.
docker run -t -i training/sinatra /bin/bash
Inside our running container let’s add the json gem.
root@0b2616b0e5a8:/# gem install json
Once this has completed let’s exit our container using the exit command.
You can then commit a copy of this container to an image using the docker commit command.
docker commit -m "Added json gem" -a "Kate Smith" \
0b2616b0e5a8 ouruser/sinatra:v2
The -m flag allows us to specify a commit message. The -a flag allows us to specify an author for our update.
Building an image with a Dockerfile
First, create a directory and a Dockerfile.
$ mkdir sinatra $ cd sinatra $ touch Dockerfile
Each instruction creates a new layer of the image.
# This is a comment FROM ubuntu:14.04 MAINTAINER Kate Smith <[email protected]> ENV REFRESHED_AT 2016-02-22 RUN apt-get update && apt-get install -y ruby ruby-dev RUN gem install sinatra
Build the image:
docker build -t ouruser/sinatra:v2 .
In this case, I've specified the ENV instruction to set an environment variable called REFRESHED_AT,showing when the template was last updated. when I want to refresh the build, I change the date in my ENV instruction.
Bypassing the Dockerfile build cache:
docker build --no-cache -t ouruser/sinatra:v2 .
Creating a container from the last successful step
docker run -t -i 997485f46ec4 /bin/bash
Launching a container from our new image
docker run -t -i ouruser/sinatra:v2 /bin/bash
Viewing our new image
docker images ouruser/sinatra:v2
Docker Hub提供了大量的image，大家可以查看学习，比如jboss/wildfly, mysql
Pushing images to the Docker Hub
docker push ouruser/sinatra:v2
Deleting an image
#This only deletes the image locally
docker rmi ouruser/sinatra:v2
Registry
Running a registry from a container
docker run -p 5000:5000 registry
This will launch a container running the registry application and bind port 5000 to the local host.
Testing the new registry
# Tagging our image for our new registry
docker tag 8dbd9e392a96 docker.example.com:5000/ouruser/sinatra:v2
# push it to the new registry
docker push docker.example.com:5000/ouruser/sinatra:v2
# Building a container from our local registry
docker run -t -i docker.example.com:5000/ouruser/sinatra:v2 /bin/bash
Reference
The Docker book
Docker Docs
Best practices for writing Dockerfiles
Dockerfile reference