Docker
Perfect — let’s go step by step to set up your VPS for a Dockerized Spring Boot deployment. Since you already have PostgreSQL running natively, I’ll include how to connect your containerized app to that DB.
This will be production-ready but simple, no Kubernetes yet.
Install Docker on your VPS
bash
Assuming Ubuntu:
# Update packages
sudo apt update && sudo apt upgrade -y
# Install Docker
sudo apt install -y docker.io
# Enable Docker to start on boot
sudo systemctl enable docker
sudo systemctl start docker
# Add your user to the docker group
sudo usermod -aG docker $USER
Log out and back in so your user is in the docker group.
Test installation:
docker run hello-world
Create a Dockerfile for your Spring Boot app
Place this in the root of your Spring Boot project:
bash
# Use Temurin Java 21 JRE as base
FROM eclipse-temurin:21-jre
# Set working directory inside container
WORKDIR /app
# Copy the Spring Boot JAR into container
COPY target/*.jar app.jar
# Expose port 8080 (default Spring Boot)
EXPOSE 8080
# Start the application
ENTRYPOINT ["java","-jar","/app/app.jar"]
This is a single-stage Docker build, simple for your VPS.
Optional: Later you can make it multi-stage (build + runtime).
Build Docker image on VPS (manual test)
From your project root:
bash
# Build Docker image
docker build -t myapp:latest .
# Run container
docker run -d --name myapp \
-p 8080:8080 \
-e SPRING_DATASOURCE_URL=jdbc:postgresql://127.0.0.1:5432/mydb \
-e SPRING_DATASOURCE_USERNAME=appuser \
-e SPRING_DATASOURCE_PASSWORD=secret \
myapp:latest
Check logs:
docker logs -f myapp
Stop / remove container:
docker stop myapp
docker rm myapp
Connect container to your native PostgreSQL
PostgreSQL is running on 127.0.0.1 (native VPS)
Container sees VPS IP as host (by default localhost inside container ≠ host)
Options:
bash
Use VPS private IP
docker run -d --name myapp \
-p 8080:8080 \
-e SPRING_DATASOURCE_URL=jdbc:postgresql://<VPS-IP>:5432/mydb \
-e SPRING_DATASOURCE_USERNAME=appuser \
-e SPRING_DATASOURCE_PASSWORD=secret \
myapp:latest
Host network mode (Linux only)
docker run -d --name myapp --network=host \
-e SPRING_DATASOURCE_URL=jdbc:postgresql://127.0.0.1:5432/mydb \
-e SPRING_DATASOURCE_USERNAME=appuser \
-e SPRING_DATASOURCE_PASSWORD=secret \
myapp:latest
Option 1 is safer and recommended.
Running your container as a service (production-style)
bash
Using systemd:
sudo nano /etc/systemd/system/myapp.service
Paste:
[Unit]
Description=My Spring Boot Docker App
After=docker.service
Requires=docker.service
[Service]
Restart=always
ExecStart=/usr/bin/docker run --rm \
--name myapp \
-p 8080:8080 \
-e SPRING_DATASOURCE_URL=jdbc:postgresql://<VPS-IP>:5432/mydb \
-e SPRING_DATASOURCE_USERNAME=appuser \
-e SPRING_DATASOURCE_PASSWORD=secret \
myapp:latest
ExecStop=/usr/bin/docker stop myapp
[Install]
WantedBy=multi-user.target
Reload and start:
sudo systemctl daemon-reload
sudo systemctl enable myapp
sudo systemctl start myapp
sudo systemctl status myapp
Optional: Automate deployment via GitHub Actions
Example steps:
bash
- name: Build JAR
run: mvn -B package
- name: Build Docker image
run: docker build -t myapp:latest .
- name: Copy Docker image to VPS
run: |
docker save myapp:latest | bzip2 | ssh user@your-vps "bunzip2 | docker load"
- name: Restart Docker container on VPS
run: ssh user@your-vps "sudo systemctl restart myapp"
This gives you full CI/CD from GitHub → VPS with Docker.
✅ TL;DR Setup Flow
Install Docker on VPS
Create Dockerfile for Spring Boot JAR
Build image locally or via CI
Run container, passing DB credentials
Use systemd to run as a service
Optionally automate with GitHub Actions
docker running image
bash
$ docker run -d -p 8080:8080 --name gnostex-backend-app --add-host=host.docker.internal:host-gateway -e SPRING_DATASOURCE_URL=jdbc:postgresql://host.docker.internal:5432/gnostexdb -e SPRING_DATASOURCE_USERNAME=gnostex -e SPRING_DATASOURCE_PASSWORD=gnostex backend-app
docker: Error response from daemon: Conflict. The container name "/backend-app" is already in use by container "2aaf2419dedcd166ce480f6e9cd693d4c004da5bd6ee57aa97628ca78b5ae950". You have to remove (or rename) that container to be able to reuse that name.
See 'docker run --help'.
$ docker rm gnostex-backend-app
Error response from daemon: You cannot remove a running container 2aaf2419dedcd166ce480f6e9cd693d4c004da5bd6ee57aa97628ca78b5ae950. Stop the container before attempting removal or force remove
$ docker rm -f gnostex-backend-app
backend-app
$ docker run -d -p 8080:8080 --name gnostex-backend-app --add-host=host.docker.internal:host-gateway -e SPRING_DATASOURCE_URL=jdbc:postgresql://host.docker.internal:5432/gnostexdb -e SPRING_DATASOURCE_USERNAME=gnostex -e SPRING_DATASOURCE_PASSWORD=gnostex backend-app
447965ce88b7f65915b669e68d8676c73d190f2be199ad360fa7eb91c29002dc
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
447965ce88b7 backend-app "java -jar /app/app.…" 7 minutes ago Up 7 minutes 0.0.0.0:8080->8080/tcp, :::8080->8080/tcp backend-app
8f2c6d596548 registry:2 "/entrypoint.sh /etc…" 14 months ago Up 15 hours 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry
gnosticka@linux:~$ docker logs gnostex-backend-app
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v3.2.5)
2025-12-21T17:30:28.318Z INFO 1 --- [gnostex-backend] [ main] a.g.g.GnostexBackendApplication : Starting GnostexBackendApplication v0.0.1-SNAPSHOT using Java 21.0.9 with PID 1 (/app/app.jar started by root in /app)
2025-12-21T17:30:28.320Z INFO 1 --- [gnostex-backend] [ main] a.g.g.GnostexBackendApplication : No active profile set, falling back to 1 default profile: "default"
.
.
.
.
gnosticka@linux:~$ docker stop 447965ce88b7
447965ce88b7
gnosticka@linux:~$
gnosticka@linux:~$
gnosticka@linux:~$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8f2c6d596548 registry:2 "/entrypoint.sh /etc…" 14 months ago Up 15 hours 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry
gnosticka@linux:~$
gnosticka@linux:~$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
backend-app latest 9ce344c390e4 11 hours ago 335MB
gnostex-backend latest 9ce344c390e4 11 hours ago 335MB
/*
Correct removal sequence
Stop the container (if running)
$ docker stop backend-app
Remove the container
$ docker rm backend-app
Now remove the image
$ docker rmi backend-app:latest
One-liner (common in dev)
$ docker rm -f backend-app && docker rmi backend-app:latest
*/
gnosticka@linux:~$ docker rmi gnostex-backend:latest
Untagged: gnostex-backend:latest
gnosticka@linux:~$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
backend-app latest 9ce344c390e4 11 hours ago 335MB
/*
docker ps
shows only running containers
Your error earlier said:
container 447965ce88b7 is using its referenced image
That means the container is stopped, not running.
Stopped containers still hold a reference to the image, so Docker won’t let you delete the image yet.
Show stopped containers
Run:
docker ps -a
You’ll see something like:
CONTAINER ID IMAGE STATUS NAMES
447965ce88b7 backend-app Exited (143) 5 mins ago backend-app
Remove the stopped container
Now remove it:
docker rm backend-app
(or by ID)
docker rm 447965ce88b7
Now remove the image
docker rmi backend-app:latest
Command Shows
docker ps running containers only
docker ps -a all containers (running + stopped)
docker images images
*/
gnosticka@linux:~$ docker rmi backend-app:latest
Error response from daemon: conflict: unable to remove repository reference "backend-app:latest" (must force) - container 447965ce88b7 is using its referenced image 9ce344c390e4
gnosticka@linux:~$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8f2c6d596548 registry:2 "/entrypoint.sh /etc…" 14 months ago Up 15 hours 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry
gnosticka@linux:~$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
447965ce88b7 backend-app "java -jar /app/app.…" 27 minutes ago Exited (143) 16 minutes ago backend-app
8f2c6d596548 registry:2 "/entrypoint.sh /etc…" 14 months ago Up 15 hours 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry
gnosticka@linux:~$ docker rm backend-app
backend-app
gnosticka@linux:~$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8f2c6d596548 registry:2 "/entrypoint.sh /etc…" 14 months ago Up 15 hours 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry
gnosticka@linux:~$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
backend-app latest 9ce344c390e4 11 hours ago 335MB
<none> <none> 4d811dc24daf 11 hours ago 630MB
eclipse-temurin 21-jdk bedd08f5f915 5 weeks ago 448MB
eclipse-temurin 21-jre 2e463b829a56 5 weeks ago 287MB
hello-world latest 1b44b5a3e06a 4 months ago 10.1kB
hello-app latest 428b9a9956ea 14 months ago 791MB
<none> <none> 5e371ca8b5ff 14 months ago 1.13GB
icr.io/appcafe/open-liberty full-java17-openj9-ubi 15fb3961abe1 14 months ago 1.09GB
icr.io/appcafe/open-liberty kernel-slim-java17-openj9-ubi be6bf4d2909b 14 months ago 692MB
localhost:5000/hello-spring-boot-jetty latest bc6ba6c5d1f2 14 months ago 436MB
hello-spring-boot-jetty latest bc6ba6c5d1f2 14 months ago 436MB
registry 2 75ef5b734af4 2 years ago 25.4MB
openjdk 17-jdk-slim 37cb44321d04 3 years ago 408MB
gnosticka@linux:~$
gnosticka@linux:~$ docker image prune
WARNING! This will remove all dangling images.
Are you sure you want to continue? [y/N] y
Deleted Images:
deleted: sha256:5e371ca8b5ff5797f24fd1f42ce59cf8bda063d84e5c9a7955f00afa9c24d131
deleted: sha256:fad6f85e48c166ed20c26720945ea05e1e4cf4f8f98c8e80b7c175895211280c
deleted: sha256:83ad60cf3aaae291e942af598e4b3442cb7ca3b9cdb318fdaf6fd72ad1649a6a
deleted: sha256:61db6d646f1aafa37b3288408cbfc7c64ee2ebff4120ad48a98eddaf6c33bebe
deleted: sha256:4d811dc24daf6f04d1d48054b9e607fae1a352342afcb464fd9664ae07d0013b
deleted: sha256:c401f4201f50f123ae479276e1aa842b4590b70a6e9c93e5154e9871af87fc49
deleted: sha256:554c66c4d5257322bc8b0a9a02bbd4ed17fb32ec71c2a6773c3d8ef7ab6f2b89
deleted: sha256:43d3fe78d20c292596f6f870919ac0dcf43686b8736e75af36f258ec49a12cc2
deleted: sha256:80425ae42e8deafcd23cfcbfac75f888e6f3aca464125e87d12f06ddb478d45c
deleted: sha256:ecf3fc40d4a35ec3994d0ed725a12bbeb39d2ed3296c244ab312e03beee53ec8
deleted: sha256:230d3afaaa4360d2a60ffd1391281db681b5b410e9f47b4c719ffcf7763cc2a6
deleted: sha256:978245a254eb5982209fd3704b722d0060b1e9fe4a1f75f957caa1075d7032ad
deleted: sha256:e5b002889a59baefe3b21290537dea86395a9606f9ba8195fc2fac36febf130a
deleted: sha256:ccbdc782387e4be0424c925dc1ffd8cd31c54f455660a0d1d9990b04a227d5b5
deleted: sha256:5dc51338ac359f58ae177f04c789fbdfa66caad5e85cb3a4dcf52d360882474e
deleted: sha256:4862cad023462c0e099841ec8446388fb29a293e34de91b103bad241aa7f297e
deleted: sha256:08d5ace6a10df25ee0b456b00f7890d79648179532f4f677ca5ab53f2d878bd6
deleted: sha256:77f142e8770d8b1cc28e33f8f92bcc79d1d8c3fd635911b17dca3520d911d7f2
Total reclaimed space: 227.2MB
gnosticka@linux:~$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
backend-app latest 9ce344c390e4 11 hours ago 335MB
eclipse-temurin 21-jdk bedd08f5f915 5 weeks ago 448MB
eclipse-temurin 21-jre 2e463b829a56 5 weeks ago 287MB
hello-world latest 1b44b5a3e06a 4 months ago 10.1kB
hello-app latest 428b9a9956ea 14 months ago 791MB
icr.io/appcafe/open-liberty full-java17-openj9-ubi 15fb3961abe1 14 months ago 1.09GB
icr.io/appcafe/open-liberty kernel-slim-java17-openj9-ubi be6bf4d2909b 14 months ago 692MB
hello-spring-boot-jetty latest bc6ba6c5d1f2 14 months ago 436MB
localhost:5000/hello-spring-boot-jetty latest bc6ba6c5d1f2 14 months ago 436MB
registry 2 75ef5b734af4 2 years ago 25.4MB
openjdk 17-jdk-slim 37cb44321d04 3 years ago 408MB
gnosticka@linux:~$
gnosticka@linux:~$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d03d8f4efaf4 hello-world "/hello" 42 minutes ago Exited (0) 42 minutes ago vigilant_franklin
38191c81464b hello-world "/hello" 44 minutes ago Exited (0) 44 minutes ago agitated_franklin
5a1513be2de8 hello-world "/hello" 44 minutes ago Exited (0) 44 minutes ago charming_galileo
eab1211520e1 hello-world "/hello" 44 minutes ago Exited (0) 44 minutes ago eager_williamson
d60d438c2f5d hello-app "/opt/ol/helpers/run…" 14 months ago Exited (255) 14 months ago 0.0.0.0:9080->9080/tcp, :::9080->9080/tcp, 0.0.0.0:9443->9443/tcp, :::9443->9443/tcp hello-app-container
bac311aa6bfa c3f4ac054889 "/opt/ol/helpers/run…" 14 months ago Exited (143) 14 months ago springBootContainer
b6cfcdbcb268 c73257c23fe0 "/opt/ol/helpers/run…" 14 months ago Exited (130) 14 months ago agitated_volhard
271621aa5faf b4a9aa4502fd "/opt/ol/helpers/run…" 14 months ago Exited (130) 14 months ago charming_greider
31f9a6c4b61d b4a9aa4502fd "/opt/ol/helpers/run…" 14 months ago Exited (130) 14 months ago exciting_borg
11a3860cb7c2 65197cca5f09 "/opt/ol/helpers/run…" 14 months ago Exited (130) 14 months ago frosty_hofstadter
8f2c6d596548 registry:2 "/entrypoint.sh /etc…" 14 months ago Up 15 hours 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry
9c0c72fb704c hello-spring-boot-jetty "java -jar app.jar" 14 months ago Exited (130) 14 months ago magical_bose
gnosticka@linux:~$ docker container prune
WARNING! This will remove all stopped containers.
Are you sure you want to continue? [y/N] y
Deleted Containers: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 reclaimed space: 7.359MB
gnosticka@linux:~$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8f2c6d596548 registry:2 "/entrypoint.sh /etc…" 14 months ago Up 15 hours 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry
/*
Pro DevOps rule of thumb
Goal Command
Safe cleanup -- docker image prune
Free real disk space -- docker image prune -a
Full reset -- docker system prune -a
Surgical cleanup -- docker rmi IMAGE
*/