DevOps Classroom Series – 17/Jun/2020

Installing Docker on Linux

1. Script Based Approach:

   • Execute the following commands on your linux instance

   curl -fsSL https://get.docker.com -o get-docker.sh
   sh get-docker.sh
   

   • Add user to docker group

2. Instruction Based Approach: Refer Here

   • Ubuntu
   • Centos

Dockerfile Instructions

• EXPOSE:
  • This instruction informs Docker that the application listens on the specific network ports at runtime.
  • Two Protocols can be specified TCP and UDP. TCP is default
  • Syntax:

  EXPOSE <port> [<port/protocol>]
  

  • Example

  FROM openjdk:8
  RUN wget https://referenceappkhaja.s3-us-west-2.amazonaws.com/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar
  EXPOSE 8080
  ENTRYPOINT ["java"]
  CMD ["-jar",  "spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar"]
  

  • Execute the following commands

  docker image build -t spc:0.1 .
  docker container run -P -d spc:0.1
  docker container ls
  
  

• LABEL:
  • This instructio adds metadata to an image
  • Syntax

  LABEL <key>=<value> <key>=<value>
  

  • Example

  FROM openjdk:8
  LABEL author="khaja"
  LABEL version="0.2"
  LABEL project="QT"
  RUN wget https://referenceappkhaja.s3-us-west-2.amazonaws.com/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar
  EXPOSE 8080
  ENTRYPOINT ["java"]
  CMD ["-jar",  "spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar"]
  

• ADD and COPY:
  • Both ADD and COPY instructions are used to copy the files into docker image.
  • ADD instruction supports copying files from url and local machines
  • COPY instructuon supports only copying files from local machines
  • Syntax:

  ADD <src> <dest>
  COPY <src> <dest>
  

  • Example ADD with URL:

  FROM openjdk:8
  LABEL author="khaja"
  LABEL version="0.3"
  LABEL project="QT"
  ADD https://referenceappkhaja.s3-us-west-2.amazonaws.com/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar  /spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar
  EXPOSE 8080
  ENTRYPOINT ["java"]
  CMD ["-jar",  "/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar"]
  

  • Example Add/Copy with local path

  FROM openjdk:8
  LABEL author="khaja"
  LABEL version="0.4"
  LABEL project="QT"
  COPY spring-petclinic.jar  /spring-petclinic.jar
  EXPOSE 8080
  ENTRYPOINT ["java"]
  CMD ["-jar",  "/spring-petclinic.jar"]