ContextQMD
Back to Docker

FromPlatformFlagConstDisallowed

_vendor/github.com/moby/buildkit/frontend/dockerfile/docs/rules/from-platform-flag-const-disallowed.md

18.09-release1.3 KB
Original Source

Output

text
FROM --platform flag should not use constant value "linux/amd64"

Description

Specifying --platform in the Dockerfile FROM instruction forces the image to build on only one target platform. This prevents building a multi-platform image from this Dockerfile and you must build on the same platform as specified in --platform.

The recommended approach is to:

  • Omit FROM --platform in the Dockerfile and use the --platform argument on the command line.
  • Use $BUILDPLATFORM or some other combination of variables for the --platform argument.
  • Stage name should include the platform, OS, or architecture name to indicate that it only contains platform-specific instructions.

Examples

❌ Bad: using a constant argument for --platform

dockerfile
FROM --platform=linux/amd64 alpine AS base
RUN apk add --no-cache git

✅ Good: using the default platform

dockerfile
FROM alpine AS base
RUN apk add --no-cache git

✅ Good: using a meta variable

dockerfile
FROM --platform=${BUILDPLATFORM} alpine AS base
RUN apk add --no-cache git

✅ Good: used in a multi-stage build with a target architecture

dockerfile
FROM --platform=linux/amd64 alpine AS build_amd64
...

FROM --platform=linux/arm64 alpine AS build_arm64
...

FROM build_${TARGETARCH} AS build
...