# FromPlatformFlagConstDisallowed


## 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
...
```