fix(deploy): 在线更新 - 在停服前校验更新器写入权限并修正 systemd 可写目录

backend/internal/hostupdate/manager_ops.go

@@ -123,6 +123,14 @@ func (m *Manager) preflight(composePath, targetVersion string) error {
 	if _, err := os.Stat(m.envPath()); err != nil {
 		return fmt.Errorf("读取部署环境：%w", err)
 	}
+	if m.config.SelfUpdate {
+		if strings.TrimSpace(m.config.BinaryPath) == "" {
+			return errors.New("检查 Host Updater 安装目录：二进制路径为空")
+		}
+		if err := checkWritableDirectory(filepath.Dir(m.config.BinaryPath)); err != nil {
+			return fmt.Errorf("检查 Host Updater 安装目录：%w", err)
+		}
+	}
 	var disk syscall.Statfs_t
 	if err := syscall.Statfs(m.config.BackupDir, &disk); err != nil {
 		return fmt.Errorf("检查备份磁盘空间：%w", err)
@@ -144,6 +152,26 @@ func (m *Manager) preflight(composePath, targetVersion string) error {
 	return nil
 }
 
+func checkWritableDirectory(directory string) error {
+	directory = strings.TrimSpace(directory)
+	if directory == "" {
+		return errors.New("Host Updater 二进制路径为空")
+	}
+	temporary, err := os.CreateTemp(directory, ".updater-write-test-*")
+	if err != nil {
+		return err
+	}
+	name := temporary.Name()
+	if closeErr := temporary.Close(); closeErr != nil {
+		_ = os.Remove(name)
+		return closeErr
+	}
+	if removeErr := os.Remove(name); removeErr != nil {
+		return removeErr
+	}
+	return nil
+}
+
 func (m *Manager) prepareUpdaterBinary(targetVersion string) (string, error) {
 	if !m.config.SelfUpdate {
 		return "", nil

backend/internal/hostupdate/manager_ops_test.go

@@ -129,3 +129,20 @@ func TestCreateBackupReadsBackendDataAsRoot(t *testing.T) {
 	}
 	t.Fatalf("backend data backup did not use root: %#v", runner.calls)
 }
+
+func TestCheckWritableDirectory(t *testing.T) {
+	directory := t.TempDir()
+	if err := checkWritableDirectory(directory); err != nil {
+		t.Fatalf("writable directory rejected: %v", err)
+	}
+	entries, err := os.ReadDir(directory)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entries) != 0 {
+		t.Fatalf("write probe was not cleaned up: %v", entries)
+	}
+	if err := checkWritableDirectory(filepath.Join(directory, "missing")); err == nil {
+		t.Fatal("missing directory was accepted")
+	}
+}