# Page Not Found

The URL `di-2-zhang-an-zhuang-freebsd/di-2.1-install-pre` does not exist. This page may have been moved, renamed, or deleted.

## Suggested Pages

You may be looking for one of the following:
- [2.6 安装故障排除](https://book.bsdcn.org/di-2-zhang-freebsd-an-zhuang-ji-chu/di-2.6-jie-an-zhuang-gu-zhang-pai-chu.md)
- [18.4 ipfirewall（IPFW）](https://book.bsdcn.org/di-18-zhang-fang-huo-qiang/di-18.4-jie-ipfirewall-ipfw.md)
- [26.10 DTrace](https://book.bsdcn.org/di-26-zhang-kai-fa-huan-jing/di-26.10-jie-dtrace.md)
- [17.4 安全等级](https://book.bsdcn.org/di-17-zhang-an-quan/di-17.4-jie-an-quan-ji-bie.md)
- [17.1 信息安全哲学](https://book.bsdcn.org/di-17-zhang-an-quan/di-17.1-jie-an-quan-zhe-xue.md)

## How to find the correct page

If the exact page cannot be found, you can still retrieve the information using the documentation query interface.

### Option 1 — Ask a question (recommended)

Perform an HTTP GET request on the documentation index with the `ask` parameter:

```
GET https://book.bsdcn.org/di-2-zhang-freebsd-an-zhuang-ji-chu/di-2.6-jie-an-zhuang-gu-zhang-pai-chu.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

### Option 2 — Browse the documentation index

Full index: https://book.bsdcn.org/sitemap.md

Use this to discover valid page paths or navigate the documentation structure.

### Option 3 — Retrieve the full documentation corpus

Full export: https://book.bsdcn.org/llms-full.txt

Use this to access all content at once and perform your own parsing or retrieval. It will be more expensive.

## Tips for requesting documentation

Prefer `.md` URLs for structured content, append `.md` to URLs (e.g., `/di-2-zhang-freebsd-an-zhuang-ji-chu/di-2.6-jie-an-zhuang-gu-zhang-pai-chu.md`).

You may also use `Accept: text/markdown` header for content negotiation.