OpenNHP/opennhp · error

failed to create file

Error message

failed to create file: %v

What it means

After passing the existence check, Save creates the key file with os.Create. If file creation fails - permission denied in the etc/ztdo directory, invalid doId producing an illegal filename, or disk full - this error is returned and no key material is persisted.

Solutions

1. Check the wrapped os error: for 'permission denied', fix ownership/permissions of <exeDir>/etc/ztdo so the process user can create files.
2. Validate doId before saving - it should be a UUID or safe identifier without path separators or illegal characters.
3. Check disk space and inodes (df / df -i) on the volume holding etc/ztdo.
4. Pre-create the directory with correct ownership, or run the daemon under an account with write access to its exe directory.

Example fix

// before: unchecked doId can build an invalid path
if err := store.Save(doId); err != nil { return err }
// after: validate doId as a UUID first
if _, err := uuid.Parse(doId); err != nil {
	return fmt.Errorf("invalid doId %q: %w", doId, err)
}
if err := store.Save(doId); err != nil { return err }

if _, err := uuid.Parse(doId); err != nil {
	return fmt.Errorf("doId must be a UUID, got %q", doId)
}
if err := syscall.Access(filepath.Join(common.ExeDirPath, "etc/ztdo"), syscall.W_OK); err != nil {
	return fmt.Errorf("etc/ztdo not writable: %w", err)
}

func validDoId(doId string) bool {
	_, err := uuid.Parse(doId)
	return err == nil
}

if err := store.Save(doId); err != nil {
	if errors.Is(errors.Unwrap(err), fs.ErrPermission) {
		return fmt.Errorf("cannot create key file; check ownership of etc/ztdo: %w", err)
	}
	return err
}

When it happens

Trigger: Calling Save(doId) when os.Create(fullPath) fails: (1) the process cannot write to the (just-created or existing) etc/ztdo directory; (2) doId contains characters making the path invalid or too long on the OS; (3) no space / inode exhaustion on the volume.

Common situations: Directory owned by root while the daemon runs unprivileged; doId with slashes from a malformed identifier; full disk on a small container volume during key provisioning.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• failed to create etc directory
• fail to write private key file
• fail to write public key file
• keystore: create directory
• failed to create etc directory

AI-assisted analysis of OpenNHP/opennhp@6e04ca5ff0 (2026-09-07). Data as JSON: /api/errors/167c7c481af8caa2. Report an issue: GitHub.

Appendix: source

Thrown at endpoints/db/utils.go:79

// Save saves the dataPrivateKeyBase64 to a file, the format of file name is data-<doId>.json
// Notes: this default way to store data private key is not safe. In the wild environment, need to use a secure way to store data private key.
func (d *DataPrivateKeyStore) Save(doId string) error {
	// Make sure the etc directory exists
	etcDir := "etc/ztdo"
	if err := os.MkdirAll(etcDir, 0755); err != nil {
		return fmt.Errorf("failed to create etc directory: %v", err)
	}

	fileName := "data-key-" + doId + ".json"
	fullPath := filepath.Join(common.ExeDirPath, etcDir, fileName)
	if _, err := os.Stat(fullPath); err == nil {
		return fmt.Errorf("%v already exists, please delete it first", fullPath)
	}

	file, err := os.Create(fullPath)
	if err != nil {
		return fmt.Errorf("failed to create file: %v", err)
	}
	defer file.Close()

	_, err = file.Write(d.toJson())
	return err
}

func (d *DataPrivateKeyStore) Delete(doId string) error {
	etcDir := "etc/ztdo"
	fileName := "data-key-" + doId + ".json"
	fullPath := filepath.Join(common.ExeDirPath, etcDir, fileName)

	// delete the file
	err := os.Remove(fullPath)
	if err != nil {
		return fmt.Errorf("failed to delete file: %v", err)
	}
	return nil

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