coreybutler/nvm-windows · error

error: failed to create backup directory: %v

Error message

error: failed to create backup directory: %v

What it means

Before overwriting the current installation, nvm-windows creates a second temp directory (nvm-backup-*) to hold a zip of the existing version. This error means os.MkdirTemp failed, i.e. the OS refused to create a directory under %TEMP%. Nothing has been modified yet at this point, so the installation is still intact.

Source

Thrown at src/upgrade/upgrade.go:469

	// Debugging
	if verbose {
		tree(tmp, "downloaded files (extracted):")
		nvmtestcmd := exec.Command(filepath.Join(tmp, "assets", "nvm.exe"), "version")
		nvmtestcmd.Stdout = os.Stdout
		nvmtestcmd.Stderr = os.Stderr
		err = nvmtestcmd.Run()
		if err != nil {
			fmt.Println("error running nvm.exe:", err)
		}
	}

	// Backup current version to zip
	status <- Status{Text: "applying update..."}
	currentExe, _ := os.Executable()
	currentPath := filepath.Dir(currentExe)
	bkp, err := os.MkdirTemp("", "nvm-backup-*")
	if err != nil {
		status <- Status{Err: fmt.Errorf("error: failed to create backup directory: %v\n", err)}
	}
	defer os.RemoveAll(bkp)

	err = zipDirectory(currentPath, filepath.Join(bkp, "backup.zip"))
	if err != nil {
		status <- Status{Err: fmt.Errorf("error: failed to create backup: %v\n", err)}
	}

	os.MkdirAll(filepath.Join(currentPath, ".update"), os.ModePerm)
	copyFile(filepath.Join(bkp, "backup.zip"), filepath.Join(currentPath, ".update", "nvm4w-backup.zip"))

	// Copy the new files to the current directory
	// copyFile(currentExe, fmt.Sprintf("%s.%s.bak", currentExe, version))
	copyDirContents(filepath.Join(tmp, "assets"), currentPath)
	copyFile(filepath.Join(tmp, "assets", "nvm.exe"), filepath.Join(currentPath, ".update/nvm.exe"))

	if verbose {
		nvmtestcmd := exec.Command(filepath.Join(currentPath, ".update/nvm.exe"), "version")

View on GitHub (pinned to 5b18223ca1)

Solutions

1. Free space on the drive hosting %TEMP% (often C:) and retry.
2. Verify TEMP/TMP: echo %TEMP% then confirm the directory exists and you can create a folder in it.
3. Run the upgrade from an elevated shell if ACLs are blocking directory creation.
4. As a workaround set TEMP/TMP to a writable local path before running nvm.

// Guarantee a writable temp root before upgrading
if err := os.MkdirTemp("", "nvm-probe-*"); err != nil {
    fmt.Println("TEMP not writable:", err)
    os.Setenv("TEMP", `D:\nvm-tmp`) // point somewhere writable
}

Fail fast and clean — nothing has been modified when this fires. Report TEMP path and suggest freeing space or redirecting TEMP.

When it happens

Trigger: TEMP/TMP environment variable pointing at a non-existent or unwritable directory; disk full on the temp drive; TEMP directory ACLs restricted (locked-down corporate machine); process running without rights to write to the resolved temp path.

Common situations: System drive full (most common on small VMs/CI); TEMP redirected to a ramdisk or network share that is unavailable; group policy restricting %TEMP% write access for the invoking user.

Related errors

• error: failed to copy update.exe: %v
• failed to open source file: %v
• failed to create destination file: %v
• failed to create destination directory %s: %v
• failed to get relative path for %s: %v

AI-assisted analysis of coreybutler/nvm-windows@5b18223ca1 (2026-08-15). Data as JSON: /api/errors/e40f8401d9eaf99a. Report an issue: GitHub.