Docker Introduction, Installation on CentOS, and Deploying a Spring Boot Application

Docker is an open‑source container engine that packages applications and their dependencies into portable images.

The article explains how to install Docker on CentOS (updating the repository, adding the Docker repo, installing the docker‑ce package, and managing the service with systemctl commands such as start, restart, stop, enable, and status).

It shows how to pull a Java 8 image using docker pull java:8 and verify the image list with docker images.

A Spring Boot project is created, the Spotify Docker Maven plugin is added to pom.xml, and a Dockerfile is written to copy the built JAR and run it with Java.

The project is packaged into a Docker image with mvn clean package docker:build, then run using

docker run --name springboot-docker -p 9999:9999 -d <image‑id>

. Container status is checked with docker ps, and logs are viewed via docker logs -f --tail=100 <container‑id>. The test endpoint can be accessed at http://<host>:9999/test.

To inspect Log4j2 file logs, the article demonstrates entering the container with docker exec -it <container‑id> /bin/bash, navigating to the log directory, and tailing info.log to see file‑based logs.