Chapter 0815 mins • intermediate
Writing Dockerfiles & Build Cache
FROM, WORKDIR, COPY, RUN, CMD & Cache Optimization
What You Will Master:
Master essential Dockerfile instructions: FROM, WORKDIR, COPY, RUN, EXPOSE, CMD
Understand layer caching rules and cache invalidation
Build custom images using `docker build -t myapp .`
Core Dockerfile Instructions
* `FROM node:22-alpine`: Sets the base image blueprint.
* `WORKDIR /app`: Sets current directory for following commands.
* `COPY package*.json ./`: Copies dependency manifests.
* `RUN npm install`: Executes shell command during build time to create layer.
* `COPY . .`: Copies application source code.
* `EXPOSE 3000`: Documents intended container listening port.
* `CMD ["npm", "start"]`: Default process executed when container starts.
Interactive Lab
Build a Custom Application Image
Build a custom application image tagged `myapp:1.0` from current directory context.
0/1 Steps Done
Step 1: Build image with tag myapp:1.0
Run `docker build -t myapp:1.0 .` in the terminal.
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