Docker Compose Configuration

Configuration of multiple docker-compose.yml service file examples.

How to install docker compose

• Download the docker-compose file

sudo curl -L https://github.com/docker/compose/releases/download/1.16.1/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose

• Add executable permission to the file.

sudo chmod +x /usr/local/bin/docker-compose

• Test installation results.

docker-compose --version

Dockerfile instructions

Before understanding Docker compose, you need to understand Dockerfile.

FROM

Specify the base image, usually the first instruction of the file, but in fact, you can also use ARG as the first instruction.

  # Format
   FROM [--platform=<platform>] <image> [AS <name>]  
   FROM [--platform=<platform>] <image>[:<tag>] [AS <name>] 
   FROM [--platform=<platform>] <image>[@<digest>] [AS <name>]

  # Usage
   FROM ubuntu
   FROM openjdk:8-jre
   FROM node:12.18.4-alpine@sha256:757574c5a2...

Parameter Description:

• [--platform=<platform>] is an optional parameter, which can be used to specify the platform of the image, such as Linux/amd64, Linux/arm64, or windows/amd64, usually the default.
• <image> is the image name, followed by :tag is the version number used to specify the image, and @digest is the content-addressable identifier (you can go to the official website for details). Generally, we only use tags. If two If neither is specified, the latest version is obtained
• [AS <name>] is the name of the current build stage, because multiple FROMs can be used in the Dockerfile to create multiple images, so using as <name> can be used in the following COPY command, use --from=<name> to refer to the image built earlier, such as copying the files generated by the previous image, etc.

ARG

This command is used to specify a variable that is passed to the build runtime. It can set a default value. When building a container with the docker build command, use --build-arg <varname>=<value> to pass parameters.

# Format
ARG <name>[=<default value>]

# Usage
ARG CODE_VERSION=laster
ARG testArg=123

# Parameter
FROM centos:7
ARG parameter=123
RUN echo $parameter

docker build --build-arg parameter=234 -t test:1.0

# Note
# ARG can be used before FROM, outside of the FROM build phase, so it cannot be used in any instructions after FROM.
ARG UBUNTU_VERSION=laster
FROM ubuntu:${UBUNTU_VERSION}

ENV

This command is used to set environment variables for the container, both during the build process and in the launched container.

# Format
ENV <key>=<value> ...

# Note
# More than one can be set, or another syntax ENV <key> <value> can be used. The official website recommends using the former, and the latter may be deleted in future versions.
# ENV variables override ARG variables

# Usage
ENV APP_VERSION=1.1.0
ENV WEB_HOME /opt/webapps

COPY

This command is used to copy files or directories from the path to the container.

# Format
COPY <src>... <dest>
COPY "<src>",... "<dest>"

# Usage
COPY test.js /opt/web/

ADD

This command is used to copy files, directories, or remote files to the image, and the tar-type compressed package file will be automatically decompressed.

# Format
ADD <src>... <dest>
ADD "<src>",... "<dest>"

# Usage
ADD test.txt /tmp/test

WORKDIR

This command sets the working directory for subsequent directives, if it does not exist, the directory will be created automatically.

# Format
WORKDIR /path/to/workdir

# Usage
WORKDIR /build

LABEL

This command is used to specify the metadata tag information of the image.

# Format
LABEL <key>=<value> <key>=<value> <key>=<value> ...

# Usage
LABEL version="1.0"
LABEL description="This text illustrates"

CMD

This command is used to set the command to be executed when the container starts after building the image.

# Format
CMD ["executable","param1","param2"]
CMD ["param1","param2"]
CMD command param1 param2

# Usage
CMD sleep 40; node server.js
CMD ["node", "server.js"]

RUN

This command is used to specify the command to be executed when building the image. The main difference between RUN and CMD is that CMD is executed when the container starts, while RUN is executed during the container construction.

# Format
RUN <command>
RUN ["executable", "param1", "param2"]

# Usage
RUN apt install -y net-tools
RUN ["/bin/bash", "-c", "echo helloworld"]

EXPOSE

This command is used to specify that the container is running on the specified port. You can specify the listening protocol. If not specified, the default is TCP.

# Format
EXPOSE <port> [<port>/<protocol>...]

# Usage
EXPOSE 80/udp
EXPOSE 80 443

VOLUME

This command is used to create a mount point with the specified name that can map the directory outside the container.

# Format
VOLUME ["/data"]

# Usage
VOLUME /myvol

Docker common commands

• build: Build container.
• ps: List all containers of the current project.
• up: Build the container and start the container, common parameters: -d background start, - specify the configuration file.
• exec: Into the specified container.
• top: View the running status of each container in the project.
• logs: View the output of the container.
• down: Stop and remove all containers and remove the corresponding network.
• rm: Remove all stalled containers.
• start/stop/restart: Start container/stop container/restart container.

Docker compose file structure

• version: Specify the compsoe version corresponding to the current file, mainly 1, 2.x and 3.x
• services: service list
  • [service-name]: service name
    • image: Specify the running image, you can directly pull the existing image for processing
    • build: Set the folder where the Dockerfile is located, which can process images that need to be built with Dockerfile
      • content: the path to store the Dockerfile
      • dockerfile: Specifies the Dockerfile filename for the build
      • args: build arguments, only accessible during the build process
    • container_name: set the container name
    • restart: restart strategy, there are no, always, no-failure, unless-stoped
    • ports: Expose the port of the container, the format is host port: container port
      • 8080:8080
    • hostname: set the hostname of the container
    • volumes: Set the mount point of the container, which can be mounted on the host, the main format is "host path":"container path"[: "access mode(w,r,rw)"]
      • /opt/data:/opt/data
      • /var/lib/mysql:/var/lib/mysql:rw
    • volumes_from: mount all data volumes of another service or container
      • service_name
      • container_name
    • environment: set environment variables
      • RACK_ENV=development
• networks: configure networks
  • app_netwotk: