> For the complete documentation index, see [llms.txt](https://hezhiqiang.gitbook.io/docker/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hezhiqiang.gitbook.io/docker/network/dns.md).

# 配置 DNS

如何自定义配置容器的主机名和 DNS 呢？秘诀就是 Docker 利用虚拟文件来挂载容器的 3 个相关配置文件。

在容器中使用 `mount` 命令可以看到挂载信息：

```bash
$ mount
/dev/disk/by-uuid/1fec...ebdf on /etc/hostname type ext4 ...
/dev/disk/by-uuid/1fec...ebdf on /etc/hosts type ext4 ...
tmpfs on /etc/resolv.conf type tmpfs ...
```

这种机制可以让宿主主机 DNS 信息发生更新后，所有 Docker 容器的 DNS 配置通过 `/etc/resolv.conf` 文件立刻得到更新。

配置全部容器的 DNS ，也可以在 `/etc/docker/daemon.json` 文件中增加以下内容来设置。

```javascript
{
  "dns" : [
    "114.114.114.114",
    "8.8.8.8"
  ]
}
```

这样每次启动的容器 DNS 自动配置为 `114.114.114.114` 和 `8.8.8.8`。使用以下命令来证明其已经生效。

```bash
$ docker run -it --rm ubuntu:18.04  cat etc/resolv.conf

nameserver 114.114.114.114
nameserver 8.8.8.8
```

如果用户想要手动指定容器的配置，可以在使用 `docker run` 命令启动容器时加入如下参数：

`-h HOSTNAME` 或者 `--hostname=HOSTNAME` 设定容器的主机名，它会被写到容器内的 `/etc/hostname` 和 `/etc/hosts`。但它在容器外部看不到，既不会在 `docker container ls` 中显示，也不会在其他的容器的 `/etc/hosts` 看到。

`--dns=IP_ADDRESS` 添加 DNS 服务器到容器的 `/etc/resolv.conf` 中，让容器用这个服务器来解析所有不在 `/etc/hosts` 中的主机名。

`--dns-search=DOMAIN` 设定容器的搜索域，当设定搜索域为 `.example.com` 时，在搜索一个名为 host 的主机时，DNS 不仅搜索 host，还会搜索 `host.example.com`。

> 注意：如果在容器启动时没有指定最后两个参数，Docker 会默认用主机上的 `/etc/resolv.conf` 来配置容器。


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