---
title: 使用 HostAliases 向 Pod /etc/hosts 文件添加条目
content_type: task
weight: 60
min-kubernetes-server-version: 1.7
---
<!--
reviewers:
- rickypai
- thockin
title: Adding entries to Pod /etc/hosts with HostAliases
content_type: task
weight: 60
min-kubernetes-server-version: 1.7
-->

<!-- overview -->

<!--
Adding entries to a Pod's `/etc/hosts` file provides Pod-level override of hostname resolution when DNS and other options are not applicable. You can add these custom entries with the HostAliases field in PodSpec.

The Kubernetes project recommends modifying DNS configuration using the `hostAliases` field
(part of the `.spec` for a Pod), and not by using an init container or other means to edit `/etc/hosts`
directly.
Change made in other ways may be overwritten by the kubelet during Pod creation or restart.
-->
当 DNS 配置以及其它选项不合理的时候，通过向 Pod 的 `/etc/hosts` 文件中添加条目，
可以在 Pod 级别覆盖对主机名的解析。你可以通过 PodSpec 的 HostAliases
字段来添加这些自定义条目。

Kubernetes 项目建议使用 `hostAliases` 字段（Pod `.spec` 的一部分）来修改 DNS 配置，
而不是通过使用 Init 容器或其他方式直接编辑 `/etc/hosts`。
以其他方式所做的更改可能会在 Pod 创建或重启过程中被 kubelet 重写。

<!-- steps -->

<!--
## Default hosts file content

Start an Nginx Pod which is assigned a Pod IP:
-->
## 默认 hosts 文件内容   {#default-hosts-file-content}

让我们从一个 Nginx Pod 开始，该 Pod 被分配一个 IP：

```shell
kubectl run nginx --image nginx
```

```
pod/nginx created
```

<!--
Examine a Pod IP:
-->
检查 Pod IP：

```shell
kubectl get pods --output=wide
```

```
NAME     READY     STATUS    RESTARTS   AGE    IP           NODE
nginx    1/1       Running   0          13s    10.200.0.4   worker0
```

<!--
The hosts file content would look like this:
-->
hosts 文件的内容如下所示：

```shell
kubectl exec nginx -- cat /etc/hosts
```

```
# Kubernetes-managed hosts file.
127.0.0.1	localhost
::1	localhost ip6-localhost ip6-loopback
fe00::0	ip6-localnet
fe00::0	ip6-mcastprefix
fe00::1	ip6-allnodes
fe00::2	ip6-allrouters
10.200.0.4	nginx
```

<!--
By default, the `hosts` file only includes IPv4 and IPv6 boilerplates like
`localhost` and its own hostname.
-->
默认情况下，`hosts` 文件只包含 IPv4 和 IPv6 的样板内容，像 `localhost` 和主机名称。

<!--
## Adding additional entries with hostAliases

In addition to the default boilerplate, you can add additional entries to the
`hosts` file.
For example: to resolve `foo.local`, `bar.local` to `127.0.0.1` and `foo.remote`,
`bar.remote` to `10.1.2.3`, you can configure HostAliases for a Pod under
`.spec.hostAliases`:
-->
## 通过 HostAliases 增加额外条目   {#adding-additional-entries-with-hostaliases}

除了默认的样板内容，你可以向 `hosts` 文件添加额外的条目。
例如，要将 `foo.local`、`bar.local` 解析为 `127.0.0.1`，
将 `foo.remote`、 `bar.remote` 解析为 `10.1.2.3`，你可以在
`.spec.hostAliases` 下为 Pod 配置 HostAliases。

{{% code_sample file="service/networking/hostaliases-pod.yaml" %}}

<!--
You can start a Pod with that configuration by running:
-->
你可以使用以下命令用此配置启动 Pod：

```shell
kubectl apply -f https://k8s.io/examples/service/networking/hostaliases-pod.yaml
```

```
pod/hostaliases-pod created
```

<!--
Examine a Pod's details to see its IPv4 address and its status:
-->
检查 Pod 详情，查看其 IPv4 地址和状态：

```shell
kubectl get pod --output=wide
```

```
NAME                READY     STATUS      RESTARTS   AGE       IP              NODE
hostaliases-pod     0/1       Completed   0          6s        10.200.0.5      worker0
```

<!--
The `hosts` file content looks like this:
-->
`hosts` 文件的内容看起来类似如下所示：

```shell
kubectl logs hostaliases-pod
```

```
# Kubernetes-managed hosts file.
127.0.0.1	localhost
::1	localhost ip6-localhost ip6-loopback
fe00::0	ip6-localnet
fe00::0	ip6-mcastprefix
fe00::1	ip6-allnodes
fe00::2	ip6-allrouters
10.200.0.5	hostaliases-pod

# Entries added by HostAliases.
127.0.0.1	foo.local	bar.local
10.1.2.3	foo.remote	bar.remote
```

<!--
with the additional entries specified at the bottom.
-->
在最下面额外添加了一些条目。

<!-- 
## Why does the kubelet manage the hosts file? {#why-does-kubelet-manage-the-hosts-file}

The kubelet manages the
`hosts` file for each container of the Pod to prevent the container runtime from
modifying the file after the containers have already been started.
Historically, Kubernetes always used Docker Engine as its container runtime, and Docker Engine would
then modify the `/etc/hosts` file after each container had started.

Current Kubernetes can use a variety of container runtimes; even so, the kubelet manages the
hosts file within each container so that the outcome is as intended regardless of which
container runtime you use.
-->
## 为什么 kubelet 管理 hosts 文件？{#why-does-kubelet-manage-the-hosts-file}

kubelet 管理每个Pod 容器的 `hosts` 文件，以防止容器运行时在容器已经启动后修改文件。
由于历史原因，Kubernetes 总是使用 Docker Engine 作为其容器运行时，而 Docker Engine 
将在容器启动后修改 `/etc/hosts` 文件。

当前的 Kubernetes 可以使用多种容器运行时；即便如此，kubelet 管理在每个容器中创建 hosts文件，
以便你使用任何容器运行时运行容器时，结果都符合预期。

{{< caution >}}
<!--
Avoid making manual changes to the hosts file inside a container.

If you make manual changes to the hosts file,
those changes are lost when the container exits.
-->
请避免手工更改容器内的 hosts 文件内容。

如果你对 hosts 文件做了手工修改，这些修改都会在容器退出时丢失。
{{< /caution >}}