Dockerfile contd

Multi-staged docker build

• Multi-staged docker build involved building image in different stages
• each stage has its own from instruction and only last stage is your application image
• Lets look at sample

FROM <image> as build
...
...

FROM <image> as test
...
...

FROM <image>
...
...

• This requires copying files from local or git into image

Samples

• Lets have a single stage where we copy the code into docker iamge
• Cloning code from git into image ADD https://github.com/dummyrepos/spring-petclinic-docker-june-25.git /usr/share/spc or we can copy the code from local folder into image ADD . /usr/share/spc
• Generally when we are building the image we might not require all the files of local folder into image, for that we create a file called as .dockerignore and specify all files and folder either directly or by patterns which we donot want to copy.
• Sample .dockerignore

.git/
.git*
k8s/
target/*
**/Dockerfile
**/docker-compose.yml
# Build output and cache directories
target/
build/
.gradle/
out/

# IDE files
.idea/
.vscode/
*.iml

# Version control
.git/
.gitignore

# Environment and configuration files (often sensitive)
.env
*.properties
*.yml
*.yaml

# Logs and temp files
*.log
tmp/

# OS-specific files
.DS_Store

• Now lets have our first stage where we build the maven package
• command mvn package
• spc requires jdk 17, so lets find a image which has maven with jdk 17
• Refer Here for changes to have multi staged docker file

Search for how to build react js application and run it on nginx

• Dockerfile

FROM node:lts AS build
ADD . /app
WORKDIR /app
RUN npm install
RUN npm run build

FROM nginx
RUN rm -rf /usr/share/nginx/html/
COPY --from=build /app/dist /usr/share/nginx/html
EXPOSE 80

• Refer Here to this repo and create a docker image