containerfile-standards

name	containerfile-standards
description	Standard Containerfile patterns for .NET API and React/Vite frontend images used in BC Gov projects: port 8080, non-root appuser, HEALTHCHECK, and runtime config.json for frontend API URL. Use when creating or modifying any Containerfile or Dockerfile for a BC Gov project.

Containerfile Standards

Shared skill — referenced by bc-gov-devops and ci-cd-pipeline. All container images for BC Gov projects must follow these patterns.

Port Rule

Always expose port 8080 inside containers. Never 80, 443, 5000, or 5005. OpenShift Routes and the AVI load balancer handle TLS externally.

---

.NET API Containerfile

FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
WORKDIR /app
COPY . .
RUN dotnet publish -c Release -o /publish

FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS runtime
WORKDIR /app
EXPOSE 8080
ENV ASPNETCORE_URLS=http://+:8080
RUN apt-get update && apt-get install -y curl && rm -rf /var/lib/apt/lists/*
RUN groupadd -r appgroup && useradd -r -g appgroup appuser
COPY --from=build /publish .
USER appuser
HEALTHCHECK --interval=30s --timeout=5s \
  CMD curl -f http://localhost:8080/health/live || exit 1
ENTRYPOINT ["dotnet", "<AppName>.dll"]

---

React / Vite Frontend Containerfile

FROM node:22-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM nginx:alpine AS runtime
EXPOSE 8080
RUN apk add --no-cache wget
RUN addgroup -S appgroup && adduser -S appuser -G appgroup
COPY --from=build /app/dist /usr/share/nginx/html
COPY nginx.conf /etc/nginx/conf.d/default.conf
USER appuser
HEALTHCHECK --interval=30s --timeout=3s \
  CMD wget -q -O /dev/null http://localhost:8080/nginx-health || exit 1

---

Runtime Config — Frontend API URL

Never bake VITE_API_URL at build time. Use a /config.json served by Nginx so one image works across dev, test, and prod.

Nginx location block

location = /config.json {
    alias /usr/share/nginx/html/config.json;
    add_header Cache-Control "no-cache";
}

React app fetch (main.jsx)

// top-level await requires build.target: 'esnext' in vite.config.js
const config = await fetch('/config.json').then(r => r.json()).catch(() => ({
  apiUrl: 'http://localhost:5200',
}));
window.__env__ = config;

The Helm chart writes config.json into the container via a ConfigMap at deploy time.

---

Common Rules

• Non-root user appuser on all containers — USER appuser as final instruction
• cap_drop: [ALL] and security_opt: [no-new-privileges: true] in compose files
• Install curl (API) or wget (frontend) for health checks
• HEALTHCHECK required on every image pointing at /health/live or /nginx-health