What causes "failed to get plugin description from executable %q: %s" in hashicorp/packer?

Verify the file at the reported path exists and is executable (chmod +x / re-download the plugin).

failed to get plugin description from executable

Error message

failed to get plugin description from executable %q: %s

What it means

DiscoverMultiPlugin wraps any failure to read a plugin binary's self-described metadata (name, version, protocol) via plugingetter.GetPluginDescription. Packer discovers multi-component plugins by exec'ing the binary and parsing its description output; if the binary cannot be executed, does not print the expected description, or crashes, discovery of that plugin fails with this wrapped message.

Solutions

Verify the file at the reported path exists and is executable (chmod +x / re-download the plugin).
Download the correct build of the plugin for your OS/architecture (e.g. via `packer plugins install`).
Run the plugin binary directly with the `packer-plugin` description arg to see the underlying crash output.
Remove stale or unrelated executables from the plugin discovery directory.

Example fix

// before: wrong arch binary copied manually, fails discovery
$ cp packer-plugin-amazon_darwin_amd64 ~/.packer.d/plugins/github.com/hashicorp/amazon
// error: failed to get plugin description from executable ...: exec format error
// after: let Packer install the matching build
$ packer plugins install github.com/hashicorp/amazon

Defensive patterns

Strategy: validation

Validate before calling

func canRun(path string) error {
  fi, err := os.Stat(path)
  if err != nil { return err }
  if fi.IsDir() { return fmt.Errorf("%s is a directory", path) }
  if fi.Mode()&0o111 == 0 { return fmt.Errorf("%s is not executable", path) }
  return nil
}

Try / catch

if err := cfg.DiscoverMultiPlugin(name, path); err != nil {
  var execErr *exec.Error
  if errors.As(err, &execErr) { /* re-download correct build */ }
  log.Printf("plugin %s unusable: %v", path, err)
}

Prevention

Install plugins with `packer plugins install` instead of manual downloads.
Verify the binary matches your OS/arch before placing it in the plugin dir.
Keep the plugin directory clean of unrelated executables.
Run the plugin binary manually to confirm it emits a description.

When it happens

Trigger: Calling PluginConfig.DiscoverMultiPlugin(pluginName, pluginPath) (directly or via Discover) with a pluginPath whose binary: does not exist or is not executable; is not a valid Packer plugin; prints malformed description output; or fails to run on the current OS/arch.

Common situations: A stale or corrupted binary in the plugin directory; downloading the wrong platform build of a plugin (e.g. linux/amd64 binary on macOS); a plugin built against an incompatible SDK that panics on startup; file permissions preventing execution; a non-plugin executable placed in the PACKER_PLUGIN_PATH or .packer.d/plugins directory.

Related errors

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/b894ac9abc58b162. Report an issue: GitHub.

Appendix: source

Thrown at packer/plugin.go:138

	return nil
}

const ForceGobEnvvar = "PACKER_FORCE_GOB"

var PackerUseProto = true

// DiscoverMultiPlugin takes the description from a multi-component plugin
// binary and makes the plugins available to use in Packer. Each plugin found in the
// binary will be addressable using `${pluginName}-${builderName}` for example.
// pluginName could be manually set. It usually is a cloud name like amazon.
// pluginName can be extrapolated from the filename of the binary; so
// if the "packer-plugin-amazon" binary had an "ebs" builder one could use
// the "amazon-ebs" builder.
func (c *PluginConfig) DiscoverMultiPlugin(pluginName, pluginPath string) error {
	desc, err := plugingetter.GetPluginDescription(pluginPath)
	if err != nil {
		return fmt.Errorf("failed to get plugin description from executable %q: %s", pluginPath, err)
	}

	canProto := desc.ProtocolVersion == "v2"
	if os.Getenv(ForceGobEnvvar) != "" && os.Getenv(ForceGobEnvvar) != "0" {
		canProto = false
	}

	// Keeps track of whether or not the plugin had components registered
	//
	// If no components are registered, we don't need to clamp usage of
	// protobuf regardless if the plugin supports it or not, as we won't
	// use it at all.
	registered := false

	pluginPrefix := pluginName + "-"
	pluginDetails := PluginDetails{
		Name:        pluginName,
		Description: desc,

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