Basic Docker Image

Basic Docker Image
What is Docker?

Docker is an improved container technology. The specific "improvement" is embodied in the fact that Docker introduces an image to the container, so that the container can be created from a pre-defined template (images), and the template is still layered.

Features that Docker often mentions:

• Lightweight, reflected in small memory usage, high density
• Fast, start in milliseconds
• Isolation, Sandbox technology is more like virtual machines

Docker technology basics:

• Namespace is the basis for container isolation, so that container A cannot see container B. 6 namespaces: User, Mnt, Network, UTS, IPC, Pid
• Cgroups: Container resource statistics and isolation. Major cgroups subsystems: cpu, blkio, device, freezer, memory
• Unionfs, typical: aufs/overlayfs, the basis for implementation of layered Images

Docker components:

• Docker ClientClient ----> initiates a request to the docker server process, such as creating, stopping, and destroying a container.
• Docker ServerServer process --> process all docker requests and manage all containers
• Docker RegistryImage repository --> the central repository for storing images, which can be seen as the scm for storing binary data

Docker Installation

Docker is easy to install and supports all mainstream operating systems, from Mac to Windows to various Linux distributions.
For details, refer to docker installation.

Common Docker commands and container operations

• Docker create # create a container but do not start it
• Docker run # create and start a container
• Docker stop # stop the container and send the SIGTERM Signal
• Docker start # start a stopped container
• Docker restart # restart a container
• Docker rm # delete a container
• Docker kill # send a signal to the container. The default value is SIGKILL.
• Docker attach # connect (enter) to a running container
• Docker wait # Blocks A container until the container stops running

Obtain container Information

• Docker ps # containers in the running status
• Docker ps-a # display all containers, including running and exiting (Exited)
• Docker inspect # Get all container information in the container
• Docker logs # view container logs (stdout/stderr)
• Docker events # Get Real-time events of the docker Server
• Docker port # display container port ing
• Docker top # display container Process Information
• Docker diff # display the changes before and after the container File System

Export container

• Docker cp # copy files or directories from the container
• Docker export # export the entire file system of the container as a tar package without information such as layers and tags

Run

• Docker exec # execute a command in the container and execute bash to enter the interactive

Image operations

• Docker images # display the list of all local images
• Docker import # create an image from a tar package, usually used in combination with export
• Docker build # Use Dockerfile to create an image (recommended)
• Docker commit # create an image from a container
• Docker rmi # delete an image
• Docker load # create an image from a tar package and use it with save
• Docker save # save an image as a tar package with layers and tag Information
• Docker history # displays the history commands for generating an image
• Docker tag # Alias for the image

Registry operations

• Docker login # log on to a registry
• Docker search # search for images from the registry Repository
• Docker pull # download the image from the repository to your local device
• Docker push # push an image to the registry Repository

Obtain the Container IP address (the Container status must be Up)

docker inspect id | grep IPAddress | cut -d '"' -f 4

Get port ing

docker inspect -f '{{range $p, $conf := .NetworkSettings.Ports}} {{$p}} -> {{(index $conf 0).HostPort}} {{end}}' id

Get Environment Variables

docker exec container_id env

Kill all running containers

docker kill $(docker ps -q)

Delete old (created a week ago) Containers

docker ps -a | grep 'weeks ago' | awk '{print $1}' | xargs docker rm

Delete A stopped container

docker rm `docker ps -a -q`

Delete all images. Be careful

docker rmi $(docker images -q)

Dockerfile

Dockerfile is the basis for docker to build images. It is also an important feature that distinguishes docker from other containers. It is with Dockerfile that docker automation and portability become possible.

Whether it is development or O & M, it is almost essential to learn to write Dockerfile, which helps you understand the operation of the entire container.

FROM: Creates a new image FROM a basic image.

FROM ubuntu 

MAINTAINER, MAINTAINER Information

MAINTAINER William <wlj@nicescale.com>

ENV, set Environment Variables

ENV TEST 1

RUN, non-interactive RUN shell command

RUN apt-get -y update RUN apt-get -y install nginx

ADD: copy an external file to the image. src can be a url.

ADD http://nicescale.com/  /data/nicescale.tgz

WORKDIR/path/to/workdir, set the working directory

WORKDIR /var/www

USER, set the USER ID

USER nginx

VULUME <# dir>, set volume

VOLUME [‘/data’]

EXPOSE: exposed ports

EXPOSE 80 443 

ENTRYPOINT ['executable', 'param1', 'param2 ']

ENTRYPOINT ["/usr/sbin/nginx"]

CMD ["param1", "param2"]

CMD ["start"]

The command that is run when docker creates and starts the iner. If ENTRYPOINT is set, CMD will be used as the parameter.

Dockerfile Best Practices

• Try to put some frequently used unchanged commands in front
• CMD and ENTRYPOINT use json arrays whenever possible

Build an image using Dockerfile

docker build csphere/nginx:1.7 .

Registry

After an image is generated from the Dockerfile build, the image must be pushed to the image repository. A private docker registry must be built inside the enterprise. This registry can be seen as a binary scm, and CI/CD should also be carried out around the registry.

Deploy registry

mkdir /registrydocker run  -p 80:5000  -e STORAGE_PATH=/registry  -v /registry:/registry  registry:2.0

Push the image to the repository

Suppose 192.168.1.2 is the address of the registry Repository:

docker tag  csphere/nginx:1.7 192.168.1.2/csphere/nginx:1.7docker push 192.168.1.2/csphere/nginx:1.7