wagoodman/dive · error

could not determine docker host: %v

Error message

could not determine docker host: %v

What it means

Returned by engineResolver.fetchArchive (dive/image/docker/engine_resolver.go:75) wrapping a failure of determineDockerHost(). That helper reads DOCKER_HOST, then DOCKER_CONTEXT, then ~/.docker/config.json (cliconfig.Load), then resolves the named context from the context store (~/.docker/contexts). Any failure loading the config file or fetching context metadata surfaces here as 'could not determine docker host: %v'.

Source

Thrown at dive/image/docker/engine_resolver.go:75

	reader, err := r.fetchArchive(ctx, id)
	if err != nil {
		return err
	}

	if err := ExtractFromImage(io.NopCloser(reader), l, p); err == nil {
		return nil
	}

	return fmt.Errorf("unable to extract from image '%s': %+v", id, err)
}

func (r *engineResolver) fetchArchive(ctx context.Context, id string) (io.ReadCloser, error) {
	var err error
	var dockerClient *client.Client

	host, err := determineDockerHost()
	if err != nil {
		return nil, fmt.Errorf("could not determine docker host: %v", err)
	}
	clientOpts := []client.Opt{client.FromEnv}
	clientOpts = append(clientOpts, client.WithHost(host))

	switch strings.Split(host, ":")[0] {
	case "ssh":
		helper, err := connhelper.GetConnectionHelper(host)
		if err != nil {
			return nil, fmt.Errorf("failed to get docker connection helper: %w", err)
		}
		clientOpts = append(clientOpts, func(c *client.Client) error {
			httpClient := &http.Client{
				Transport: &http.Transport{
					DialContext: helper.Dialer,
				},
			}
			return client.WithHTTPClient(httpClient)(c)
		})

View on GitHub (pinned to d6c691947f)

Solutions

1. Validate the config: docker context ls and docker info - if the docker CLI itself errors, fix that first
2. Check ~/.docker/config.json parses (jq . ~/.docker/config.json) and has sane permissions
3. Remove or recreate the stale context: docker context rm <name> && docker context create ...; or docker context use default
4. Bypass context resolution for the dive run: DOCKER_HOST=unix:///var/run/docker.sock dive docker://<image>

Example fix

# before: stale context referenced in config
$ dive docker://alpine
Error: could not determine docker host: ...

# after: pin the host explicitly for this run
$ DOCKER_HOST=unix:///var/run/docker.sock dive docker://alpine

// pre-flight docker environment check
func dockerEnvOK() error {
    if os.Getenv("DOCKER_HOST") != "" {
        return nil // explicit host wins; no context resolution needed
    }
    if b, err := os.ReadFile(filepath.Join(os.Getenv("HOME"), ".docker", "config.json")); err == nil {
        if !json.Valid(b) {
            return fmt.Errorf("~/.docker/config.json is not valid JSON")
        }
    }
    return nil
}

reader, err := resolver.Fetch(ctx, id)
if err != nil && strings.Contains(err.Error(), "could not determine docker host") {
    // recover by pinning the host explicitly for this process
    os.Setenv("DOCKER_HOST", "unix:///var/run/docker.sock")
    reader, err = resolver.Fetch(ctx, id)
}
if err != nil {
    return err
}

When it happens

Trigger: Malformed ~/.docker/config.json (bad JSON, wrong perms) that cliconfig.Load rejects; DOCKER_CONTEXT (or config's currentContext) naming a context whose metadata cannot be read - deleted context dir, partial write, version-incompatible context store.

Common situations: Manually edited or tool-generated docker config files; contexts created by Docker Desktop removed out-of-band; home-dir sync/restore that half-copied ~/.docker/contexts; switching between Docker Desktop and plain engine installs.

Related errors

• cannot determine image provider for build: %w
• cannot determine image provider to fetch from: %w
• cannot find docker client executable
• failed to get docker connection helper: %w
• evaluation failed

AI-assisted analysis of wagoodman/dive@d6c691947f (2026-08-15). Data as JSON: /api/errors/bd32b664e7ed9d4a. Report an issue: GitHub.