hashicorp/nomad · critical

failed creating temporary directory for the AllocDir: %v

Error message

failed creating temporary directory for the AllocDir: %v

What it means

When no custom alloc_dir is configured, the client creates a temporary directory with os.MkdirTemp("", "NomadClient") during init. If this OS call fails, startup aborts with this error. It means the system temp root itself is unusable.

Source

Thrown at client/client.go:749

	}

	// Ensure the alloc mounts dir exists if we are configured with a custom path.
	if conf.AllocMountsDir != "" {
		if err := os.MkdirAll(conf.AllocMountsDir, 0o711); err != nil {
			return fmt.Errorf("failed creating alloc mounts dir: %w", err)
		}
	}

	// Ensure the alloc dir exists if we are configured with a custom path.
	if conf.AllocDir != "" {
		if err := os.MkdirAll(conf.AllocDir, 0o711); err != nil {
			return fmt.Errorf("failed creating alloc dir: %w", err)
		}
	} else {
		// Otherwise make a temp directory to use.
		p, err := os.MkdirTemp("", "NomadClient")
		if err != nil {
			return fmt.Errorf("failed creating temporary directory for the AllocDir: %v", err)
		}

		p, err = filepath.EvalSymlinks(p)
		if err != nil {
			return fmt.Errorf("failed to find temporary directory for the AllocDir: %v", err)
		}

		// Change the permissions to have the execute bit
		if err := os.Chmod(p, 0o711); err != nil {
			return fmt.Errorf("failed to change directory permissions for the AllocDir: %v", err)
		}

		conf = c.UpdateConfig(func(c *config.Config) {
			c.AllocDir = p
			c.AllocMountsDir = p
		})
	}

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Ensure TMPDIR (or /tmp) exists, is writable by the nomad user, and has free space: ls -ld "$TMPDIR" && df -h "$TMPDIR".
2. Fix or unset a bad TMPDIR environment variable for the Nomad service (e.g. in the systemd unit).
3. Configure an explicit alloc_dir so the temp directory path is never used.

Example fix

// before (systemd unit)
Environment=TMPDIR=/var/tmp/nomad  # directory missing
// after
ExecStartPre=/usr/bin/mkdir -p /var/tmp/nomad
Environment=TMPDIR=/var/tmp/nomad
# or set client { alloc_dir = "/var/lib/nomad/alloc" }

tmp := os.TempDir()
if fi, err := os.Stat(tmp); err != nil || !fi.IsDir() {
    return fmt.Errorf("TMPDIR %q invalid: %v", tmp, err)
}
probe, err := os.MkdirTemp(tmp, "NomadClientProbe")
if err != nil {
    return fmt.Errorf("cannot create temp dir: %v", err)
}
os.Remove(probe)

if err := clientInit(); err != nil {
    if strings.Contains(err.Error(), "failed creating temporary directory for the AllocDir") {
        // fix TMPDIR or set explicit alloc_dir, then restart
    }
}

When it happens

Trigger: client init without alloc_dir configured: os.MkdirTemp("", "NomadClient") returns error (typically because TMPDIR//tmp is missing, unwritable, or the disk is full).

Common situations: Containers with no /tmp, TMPDIR pointing to a non-existent path, full tmpfs (/tmp mounted with small size), or restrictive permissions on the temp root.

Related errors

• failed to find temporary directory for the StateDir: %v
• failed to open state database: %v
• failed creating alloc mounts dir: %w
• failed creating alloc dir: %w
• failed to find temporary directory for the AllocDir: %v

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/55f37afb3ea295fb. Report an issue: GitHub.