hashicorp/nomad · error

default_ipc_mode must be %q or %q, got %q

Error message

default_ipc_mode must be %q or %q, got %q

What it means

Config.validate() also checks default_ipc_mode (the default IPC namespace mode) against executor.IsolationModePrivate and executor.IsolationModeHost. Anything else fails driver configuration with this error.

Source

Thrown at drivers/java/driver.go:152

	// exec-based task drivers.
	DefaultModeIPC string `codec:"default_ipc_mode"`

	// AllowCaps configures which Linux Capabilities are enabled for tasks
	// running on this node.
	AllowCaps []string `codec:"allow_caps"`
}

func (c *Config) validate() error {
	switch c.DefaultModePID {
	case executor.IsolationModePrivate, executor.IsolationModeHost:
	default:
		return fmt.Errorf("default_pid_mode must be %q or %q, got %q", executor.IsolationModePrivate, executor.IsolationModeHost, c.DefaultModePID)
	}

	switch c.DefaultModeIPC {
	case executor.IsolationModePrivate, executor.IsolationModeHost:
	default:
		return fmt.Errorf("default_ipc_mode must be %q or %q, got %q", executor.IsolationModePrivate, executor.IsolationModeHost, c.DefaultModeIPC)
	}

	badCaps := capabilities.Supported().Difference(capabilities.New(c.AllowCaps))
	if !badCaps.Empty() {
		return fmt.Errorf("allow_caps configured with capabilities not supported by system: %s", badCaps)
	}

	return nil
}

// TaskConfig is the driver configuration of a taskConfig within a job
type TaskConfig struct {
	// Class indicates which class contains the java entry point.
	Class string `codec:"class"`

	// ClassPath indicates where class files are found.
	ClassPath string `codec:"class_path"`

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Set default_ipc_mode to exactly "private" or "host".
2. Verify the key targets IPC, not PID mode (the sibling error message names default_ipc_mode).
3. Re-run nomad agent validate on the config file to catch it before deployment.

Example fix

// before
plugin "java" {
  default_ipc_mode = "share"
}
// after
plugin "java" {
  default_ipc_mode = "host"
}

mode := cfg["default_ipc_mode"]
if mode != "" && mode != "private" && mode != "host" {
    return fmt.Errorf("default_ipc_mode must be 'private' or 'host', got %q", mode)
}

if err := driver.SetConfig(cfg); err != nil && strings.Contains(err.Error(), "default_ipc_mode") {
    return fmt.Errorf("fix default_ipc_mode in driver plugin config: %w", err)
}

When it happens

Trigger: Driver plugin config containing default_ipc_mode with a value other than "private" or "host".

Common situations: Typos like "share" or "hostMode"; case mismatches ("Private"); mixing up pid_mode and ipc_mode config keys.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• default_pid_mode must be %q or %q, got %q
• allow_caps configured with capabilities not supported by sys
• pid_mode must be %q or %q, got %q
• ipc_mode must be %q or %q, got %q
• jar_path or class must be specified

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/c9d82cb1f22b7a2b. Report an issue: GitHub.