slimtoolkit/slim · error

invalid context directory

Error message

invalid context directory

What it means

ErrInvalidContextDir is thrown by pkg/app/master/builder/image_builder.go when the directory given as a Docker build context is not usable — it does not exist or is not a valid build context. NewBasicImageBuilder / the docker build flow validates the context directory before sending it to the Docker daemon, since building requires a readable context containing a Dockerfile.

Source

Thrown at pkg/app/master/builder/image_builder.go:22

	"bytes"
	"errors"
	"fmt"
	"path/filepath"
	"strings"

	"github.com/slimtoolkit/slim/pkg/app/master/config"
	"github.com/slimtoolkit/slim/pkg/consts"
	"github.com/slimtoolkit/slim/pkg/docker/dockerfile"
	"github.com/slimtoolkit/slim/pkg/util/fsutil"

	docker "github.com/fsouza/go-dockerclient"
	log "github.com/sirupsen/logrus"
)

//todo: move/refactor this to be a "pkg/imagebuilder" engine

var (
	ErrInvalidContextDir = errors.New("invalid context directory")
)

// BasicImageBuilder creates regular container images
type BasicImageBuilder struct {
	ShowBuildLogs bool
	BuildOptions  docker.BuildImageOptions
	APIClient     *docker.Client
	BuildLog      bytes.Buffer
}

// ImageBuilder creates new optimized container images
type ImageBuilder struct {
	BasicImageBuilder
	RepoName       string
	AdditionalTags []string
	ID             string
	Entrypoint     []string
	Cmd            []string

View on GitHub (pinned to 81940d17fa)

Solutions

1. Verify the ContextDir value passed to NewBasicImageBuilder exists and is a directory (os.Stat, MkdirAll if needed)
2. Check file permissions on the directory so the process can read it
3. Run the tool from the directory you intend to use as the build context, or pass an absolute path

Example fix

// before
opts := docker.BuildImageOptions{ContextDir: "./buid-context"}
// after
if _, err := os.Stat("./build-context"); err != nil {
	os.MkdirAll("./build-context", 0755)
}
opts := docker.BuildImageOptions{ContextDir: "./build-context"}

info, err := os.Stat(ctxDir)
if err != nil || !info.IsDir() {
	return fmt.Errorf("build context %q is not a directory", ctxDir)
}

When it happens

Trigger: Calling dockerutils/build via NewBasicImageBuilder with BuildImageOptions.ContextDir pointing to a non-existent path, a file instead of a directory, or a directory without read permission.

Common situations: Typos in the --build-path/context-dir flag; running docker-slim from a different working directory than expected; CI checkouts that did not create the context dir; pointing at a Dockerfile file instead of its parent directory.

Related errors

• invalid context directory - %s
• source is symlink
• no service image
• start monitor timeout
• no docker info

AI-assisted analysis of slimtoolkit/slim@81940d17fa (2026-08-31). Data as JSON: /api/errors/2d5769303d4957a3. Report an issue: GitHub.