docker/cli · error

unable to open Dockerfile: %w

Error message

unable to open Dockerfile: %w

What it means

Error "unable to open Dockerfile: %w" thrown in docker/cli.

Source

Thrown at cli/command/image/build.go:244

	}

	switch contextType {
	case build.ContextTypeStdin:
		// buildCtx is tar archive. if stdin was dockerfile then it is wrapped
		buildCtx, relDockerfile, err = build.GetContextFromReader(dockerCli.In(), options.dockerfileName)
		if err != nil {
			return fmt.Errorf("unable to prepare context from STDIN: %w", err)
		}
	case build.ContextTypeLocal:
		contextDir, relDockerfile, err = build.GetContextFromLocalDir(options.context, options.dockerfileName)
		if err != nil {
			return fmt.Errorf("unable to prepare context: %s", err)
		}
		if strings.HasPrefix(relDockerfile, ".."+string(filepath.Separator)) {
			// Dockerfile is outside build-context; read the Dockerfile and pass it as dockerfileCtx
			dockerfileCtx, err = os.Open(options.dockerfileName)
			if err != nil {
				return fmt.Errorf("unable to open Dockerfile: %w", err)
			}
			defer dockerfileCtx.Close()
		}
	case build.ContextTypeGit:
		var tempDir string
		tempDir, relDockerfile, err = build.GetContextFromGitURL(options.context, options.dockerfileName)
		if err != nil {
			return fmt.Errorf("unable to prepare context: %w", err)
		}
		defer func() {
			_ = os.RemoveAll(tempDir)
		}()
		contextDir = tempDir
	case build.ContextTypeRemote:
		buildCtx, relDockerfile, err = build.GetContextFromURL(progBuff, options.context, options.dockerfileName)
		if err != nil && options.quiet {
			_, _ = fmt.Fprintln(dockerCli.Err(), progBuff)
		}

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at cli/command/image/build.go:244 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/fc86b34b42f3aa05.json. Report an issue: GitHub.