Dockerfile basic commands

Dockerfile basic commands

FROM-based on base image

• FROM centos # Based on centos:latest
• FROM scratch # does not rely on any base image base image
• FROM tomcat:9.0.22-jdk8-openjdk

LABEL & MAINTAINER-Information

• MAINTAINER xxxx.com
  • Institution & Personal ID
• LABEL version=“1.0”
• LABEL description="This is the description information"

WORKDIR-Set the working directory

• WORKDIR /usr/local
• WORKDIR /usr/local/newdir # automatic creation
• Try to use absolute paths

ADD & COPY-copy files

• ADD hello / # Copy to the root directory
• ADD test.tar.gz / # Add to the root directory and unzip
• In addition to copying, ADD also has the function of adding remote files

ENV-set environment constant

• ENV JAVA_HOME /usr/local/openjdk8
• RUN ${JAVA_HOME}/bin/java -jar test.jar
• Use environment constants as much as possible to improve program maintainability

Dockerfile execution instructions

RUN & CMD & ENTRYPOINT

• RUN: execute commands during Build

  • RUN yum install -y vim # Shell command format
    • Will spawn a subshell process
  • RUN ["yum", "install", "-y", "vim"] # Exec command format
    • Will replace the current process with the Exec process and keep the PID unchanged
    • After the execution is complete, exit directly without returning to the previous process environment
    • It is recommended to use the Exec command format to execute commands

• ENTRYPOINT: The command executed when the container starts

  • Only the last entrypoint in the Dockerfile will be executed
  • ENTRYPOINT["ps"] # Exec format is recommended

• CMD: execute the default command or parameter after the container is started

  • CMD is used to set the command executed by default
  • If there are multiple CMDs in the Dockerfile, only the last one will be executed
  • If additional instructions are added when the container is started, CMD will be ignored
  • CMD ["ps", "-ef"] # Exec format is recommended

• For example

FROM centos
RUN ["echo", "image building!!!"]
ENTRYPOINT ["ps"]
CMD ["-ef"]

Dockerfile combat-building a Redis image

FROM centos
RUN ["yum", "install", "-y", "gcc", "gcc-c++", "net-tools", "make"]
WORKDIR /usr/local
ADD redis-4.0.14.tar.gz .
WORKDIR /usr/local/redis-4.0.14/src
RUN make && make install
WORKDIR /usr/local/redis-4.0.14
ADD redis-7000.conf .
EXPOSE 7000
CMD ["redis-server", "redis-7000.conf"]

• Build image
  • docker build -t python_id.com/docker-redis .