Billionmail/BillionMail · error

unrar command not found, please install it first

Error message

unrar command not found, please install it first

What it means

UnrarWithExternalCommand extracts rar archives by invoking the external 'unrar' CLI. It first runs exec.LookPath("unrar"); when the binary is missing from PATH it returns this error without attempting extraction. Unlike compression, the underlying Go rar library only reads archives, but this function specifically depends on the external tool being present.

Source

Thrown at core/internal/service/compress/rar.go:232

// Unrar rar decompression
// @author <2024-06-09>
func Unrar(src, dst string) error {
	return defaultRarUnpacker.Decompress(src, dst)
}

// Rar compresses files or directories into a rar archive
// @author <2024-06-09>
func Rar(dst string, srcList ...string) error {
	return defaultRarUnpacker.Compress(dst, srcList...)
}

// UnrarWithExternalCommand decompresses a rar file using external rar command
// This is an alternative method using the external rar command
func UnrarWithExternalCommand(src, dst string) error {
	// check if 'unrar' command exists
	_, err := exec.LookPath("unrar")
	if err != nil {
		return errors.New("unrar command not found, please install it first")
	}

	// get absolute paths
	srcAbs, err := filepath.Abs(src)
	if err != nil {
		return err
	}

	dstAbs, err := filepath.Abs(dst)
	if err != nil {
		return err
	}

	// ensure destination directory exists
	if err := os.MkdirAll(dstAbs, 0755); err != nil {
		return err
	}

View on GitHub (pinned to fc36c76c05)

Solutions

1. Install unrar (apt-get install unrar / apk add unrar / UnRAR for Windows) and verify with `which unrar`
2. Add unrar to the deployment Dockerfile
3. Use RarUnpacker's built-in Decompress (pure-Go read) instead of the external-command variant
4. Pre-check exec.LookPath("unrar") at service startup and fail fast with a clear setup message

Example fix

// before
cmd := exec.Command("unrar", "x", "-o+", src, dst)
// after (Dockerfile)
RUN apt-get update && apt-get install -y --no-install-recommends unrar && rm -rf /var/lib/apt/lists/*

if _, err := exec.LookPath("unrar"); err != nil {
	return fmt.Errorf("unrar is not installed: %w", err)
}

if err := UnrarWithExternalCommand(src, dst); err != nil && strings.Contains(err.Error(), "unrar command not found") {
	// fall back to the built-in pure-Go Decompress or install unrar
}

When it happens

Trigger: Calling UnrarWithExternalCommand(src, dst) on hosts where unrar is not installed (minimal Docker images, CI runners, Windows without UnRAR.exe on PATH).

Common situations: Alpine/slim images lacking unrar; PATH not including /usr/local/bin in systemd or docker exec contexts; confusing rar (compressor) with unrar (extractor) — installing one does not provide the other.

Related errors

• rar command not found, please install it first
• disk quota exceeded
• illegal file path:
• source file/directory does not exist: %s
• rar compression failed: %s - %s

AI-assisted analysis of Billionmail/BillionMail@fc36c76c05 (2026-09-05). Data as JSON: /api/errors/6a3d9c428f780dd4. Report an issue: GitHub.