DevOps Classroom Series – 19/Mar/2021
Dockerfile
- Docker can build images by reading instructions from a Dockerfile
- Lets take one more application as an example
- This application is based on java
- This application runs on port 8080
- Lets try to install this java application on a linux machine first
- create a ubuntu linux vm on any cloud. login into linux machine using ssh
- install java
- download spring pet clinic application
sudo apt update
sudo apt install openjdk-8-jdk -y
java -version
wget https://referenceappkhaja.s3-us-west-2.amazonaws.com/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar
java -jar spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar
- Now navigate to http://publicip:8080
- To create a docker
- We have to choose a right base image
- You can choose ubuntu and perform all the steps
- Choose a image where java is already installed
- We have to choose a right base image
- To build Dockerfile we will be using instructions Refer Here
- So lets build a Dockerfile using ubuntu:18.04 image
- To set the base image we will be using FROM instrution Refer Here
- Now we need to divide our commands which we use to install/configure our application into two sections
- application installation/configuration steps. All the configuration steps we will be using can be written in Dockerfile with RUN instruction Refer Here
apt update apt install openjdk-8-jdk wget -y wget https://referenceappkhaja.s3-us-west-2.amazonaws.com/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar- application execution steps. Execution steps will be configured with instruction CMD Refer Here
java -jar spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar- Our application when executed might require some port to connect, in this case the port is 8080, we use EXPOSE instruction to specify ports of application Refer Here
- Create a folder and then place the Dockerfile in it. Now build the docker image using docker image build command Refer Here
docker image build -t spc:ubuntu .
- Now lets check the docker images in the local machine (local repository) docker image ls Refer Here
- Building a Image using openjdk image
- To copy the jar file into container use the ADD instruction Refer Here
- Lets try to build the docker image
docker image build -t spc:openjdk .
- Lets view the docker image in the local registry
- Now lets try to run the application in a docker container using two images which we have built
- To build a docker image for an app we will have multiple approaches, try to use the approach which is simpler and which results in consuming less resources
- Refer Here for the dockerfiles used in the class room
- Refer Here for the slim version of spc
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