require-dockerfile-first-instruction-from

Require the first non-comment Dockerfile instruction to be FROM.

Targeted pattern scope

• Repository-root Dockerfile instruction order.

What this rule reports

This rule reports Dockerfiles where a meaningful instruction appears before FROM.

Why this rule exists

Dockerfile semantics require a base image stage; ensuring FROM appears first keeps files valid and predictable.

❌ Incorrect

WORKDIR /app
FROM node:22-alpine

✅ Correct

# syntax=docker/dockerfile:1
FROM node:22-alpine
WORKDIR /app

When not to use it

Disable this rule only if Dockerfiles are generated and guaranteed valid by another controlled step.

Rule catalog ID: R112

Further reading

• Dockerfile reference: FROM