diff --git a/appendix/debug.md b/appendix/debug.md
index 7b33a60..eecee49 100644
--- a/appendix/debug.md
+++ b/appendix/debug.md
@@ -42,8 +42,13 @@ $ docker system prune
 ```
 如果你只是想 “恢复出厂设置”，在 Docker Desktop 里也提供了相应入口。
 
+只有在确认要丢弃本机全部镜像、容器、卷和构建缓存，并且已经停止 Docker 服务、完成备份或导出后，才考虑删除 Docker 数据目录：
+
 ```bash
+$ sudo systemctl stop docker containerd
+$ sudo cp -a /var/lib/docker /var/lib/docker.backup
 $ sudo rm -rf /var/lib/docker
+$ sudo systemctl start docker
 ```
 
 ### 常见故障排查
diff --git a/appendix/faq/errors.md b/appendix/faq/errors.md
index 267eaf4..0a4df51 100644
--- a/appendix/faq/errors.md
+++ b/appendix/faq/errors.md
@@ -3,7 +3,7 @@
 | 错误信息 / 现象 | 可能原因 | 解决方案 |
 | :--- | :--- | :--- |
 | `Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?` | Docker 服务未启动 | Linux: `sudo systemctl start docker`<br>Mac/Win: 启动 Docker Desktop |
-| `permission denied while trying to connect to the Docker daemon socket` | 当前用户不在 `docker` 用户组 | `sudo usermod -aG docker $USER` (需重新登录) |
+| `permission denied while trying to connect to the Docker daemon socket` | 当前用户无权访问 Docker socket | 临时使用 `sudo docker ...`，或确认风险后执行 `sudo usermod -aG docker $USER` 并重新登录；`docker` 用户组等同授予 root 级权限，安全要求较高的环境优先评估 Rootless mode |
 | `manifest for ... not found: manifest unknown` | 镜像 tag 不存在 | 检查 Docker Hub 该镜像是否存在该 tag，或拼写是否正确 |
 | `connection refused` (pull image) | 网络不通或镜像源无法访问 | 检查网络，配置[镜像加速器](../../03_install/3.9_mirror.md) |
 | `Bind for 0.0.0.0:8080 failed: port is already allocated` | 端口被占用 | 检查占用端口的进程 (`lsof -i:8080`) 并杀掉，或换个端口映射 (`-p 8081:80`) |
diff --git a/package.json b/package.json
index 431056e..97bcc89 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "docker_practice",
   "version": "1.9.2",
   "description": "docker_practice",
-  "main": "index.js",
+  "private": true,
   "devDependencies": {
     "vuepress": "1.9.10",
     "vuepress-plugin-container": "^2.1.5",