hashicorp/nomad · error

Failed to write data to file %q, err: %w

Error message

Failed to write data to file %q, err: %w

What it means

Thrown by `writeBytes` when the write to the already-created file fails. The file was opened successfully but `fh.Write(data)` returned an error — typically disk full (ENOSPC), I/O error, or the file descriptor becoming invalid. Nomad reports the path along with the OS error.

Source

Thrown at command/operator_debug.go:1423

		return fmt.Errorf("failed to create parent directories of %q: %w", dirPath, err)
	}

	// Ensure filename doesn't escape the sandbox of the capture directory
	escapes := escapingfs.PathEscapesSandbox(c.collectDir, filePath)
	if escapes {
		return fmt.Errorf("file path %q escapes capture directory %q", filePath, c.collectDir)
	}

	// Create the file
	fh, err := os.Create(filePath)
	if err != nil {
		return fmt.Errorf("failed to create file %q, err: %w", filePath, err)
	}
	defer fh.Close()

	_, err = fh.Write(data)
	if err != nil {
		return fmt.Errorf("Failed to write data to file %q, err: %w", filePath, err)
	}
	return nil
}

// newFilePath returns a validated filepath rooted in the provided directory and
// path. It has been checked that it falls inside the sandbox and has been added
// to the manifest tracking.
func (c *OperatorDebugCommand) newFilePath(dir, file string) (string, error) {

	// Replace invalid characters in filename
	filename := helper.CleanFilename(file, "_")

	relativePath := filepath.Join(dir, filename)
	c.manifest = append(c.manifest, relativePath)
	dirPath := filepath.Join(c.collectDir, dir)
	filePath := filepath.Join(dirPath, filename)

	// Ensure parent directories exist

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Free disk space on the volume holding the capture directory (ENOSPC is the most common cause).
2. Write the bundle to a different, larger volume via the output flag.
3. If on a network filesystem, retry writing to local disk instead.
4. Check `dmesg`/system logs for underlying block-device I/O errors and address hardware issues.

Example fix

// before (shell)
nomad operator debug -output /var/log   # 99% full
// after
df -h && nomad operator debug -output /var/tmp/debug

if usage, err := diskusage(dir); err == nil && usage.Free < minRequiredBytes {
    return fmt.Errorf("insufficient space on %s: %d bytes free", dir, usage.Free)
}

if err := c.writeBytes(dir, filename, resp, respErr); err != nil {
    if strings.Contains(err.Error(), "no space left") {
        // switch to an alternate output location or free space, then retry
    }
    return err
}

When it happens

Trigger: fh.Write failing mid-collection: no space left on device during a large debug bundle, underlying storage I/O error, or write to a file on a network mount that dropped.

Common situations: Collecting debug bundles on nodes with nearly-full disks; NFS/EFS mounts timing out; hardware/storage failures on the node.

Related errors

• write error, wrote %d bytes of %d: %v
• could not copy file: %v
• failed to write snapshot file: %v
• unable to read rooted allocation directory
• can't seek to offset %d: %w

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/94ced950bc14af2b. Report an issue: GitHub.