docker/cli · error

invalid argument: can't use stdin for both build context and

Error message

invalid argument: can't use stdin for both build context and dockerfile

What it means

docker build reads the build context and optionally the Dockerfile from stdin, but stdin is a single stream and cannot serve both. This check fires when the Dockerfile flag is '-' (options.dockerfileFromStdin()) while the build context argument was also detected as stdin (build.ContextTypeStdin, i.e. the PATH argument is '-'). Allowing both would make the CLI consume the same stream twice, so it is rejected up front as an invalid argument.

Source

Thrown at cli/command/image/build.go:210

		buildBuff     io.Writer
		remote        string
	)

	if options.platform != "" {
		_, err := platforms.Parse(options.platform)
		if err != nil {
			return err
		}
	}

	contextType, err := build.DetectContextType(options.context)
	if err != nil {
		return err
	}

	if options.dockerfileFromStdin() {
		if contextType == build.ContextTypeStdin {
			return errors.New("invalid argument: can't use stdin for both build context and dockerfile")
		}
		dockerfileCtx = dockerCli.In()
	}

	progBuff = dockerCli.Out()
	buildBuff = dockerCli.Out()
	if options.quiet {
		progBuff = bytes.NewBuffer(nil)
		buildBuff = bytes.NewBuffer(nil)
	}
	if options.imageIDFile != "" {
		// Avoid leaving a stale file if we eventually fail
		if err := os.Remove(options.imageIDFile); err != nil && !os.IsNotExist(err) {
			return fmt.Errorf("removing image ID file: %w", err)
		}
	}

	switch contextType {

View on GitHub (pinned to e9452d6e78)

Solutions

1. Pick one stdin use: pipe only the Dockerfile with a directory context: `docker build -f - . < Dockerfile`.
2. Or pipe only the context and include the Dockerfile inside it: `tar c . | docker build -` (the tar must contain the Dockerfile).
3. If the Dockerfile is generated, write it to a temp file and pass `-f /tmp/Dockerfile.gen .` instead of '-'.

Example fix

# before
cat Dockerfile | docker build -f - -
# after
cat Dockerfile | docker build -f - .

When it happens

Trigger: `docker build -f - -` or equivalents: build context PATH given as '-' combined with `--file -` (or -f -). Also hit when a script pipes a tar context on stdin and separately sets DOCKERFILE input to '-'.

Common situations: CI pipelines that pipe a tarred context (`tar c . | docker build -`) while a shared wrapper adds `-f -` to inject a generated Dockerfile; copy-pasted one-liners like `cat Dockerfile | docker build -f - -`; Makefiles composing flags from variables where both default to '-'.

Related errors

• error reading from STDIN: data is empty
• content size not available for stdin
• requested load from stdin, but stdin is empty
• the --password-stdin option requires --username to be set
• error reading from STDIN: data is empty

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/33ef021411ec2cb3.json. Report an issue: GitHub.