---
title: 理解 Kubernetes 对象
content_type: concept
weight: 10
card: 
  name: concepts
  weight: 40
---

<!---
title: Understanding Kubernetes Objects
content_type: concept
weight: 10
card: 
  name: concepts
  weight: 40
-->

<!-- overview -->
<!--
This page explains how Kubernetes objects are represented in the Kubernetes API, and how you can express them in `.yaml` format.
-->
本页说明了在 Kubernetes API 中是如何表示 Kubernetes 对象的，
以及使用 `.yaml` 格式的文件表示 Kubernetes 对象。

<!-- body -->
<!--
## Understanding Kubernetes Objects

*Kubernetes objects* are persistent entities in the Kubernetes system. Kubernetes uses these
entities to represent the state of your cluster. Specifically, they can describe:

* What containerized applications are running (and on which nodes)
* The resources available to those applications
* The policies around how those applications behave, such as restart policies, upgrades, and fault-tolerance
-->
## 理解 Kubernetes 对象    {#kubernetes-objects}

在 Kubernetes 系统中，**Kubernetes 对象** 是持久化的实体。
Kubernetes 使用这些实体去表示整个集群的状态。
比较特别地是，它们描述了如下信息：

* 哪些容器化应用正在运行（以及在哪些节点上运行）
* 可以被应用使用的资源
* 关于应用运行时表现的策略，比如重启策略、升级策略以及容错策略

<!--
A Kubernetes object is a "record of intent" - once you create the object, 
the Kubernetes system will constantly work to ensure that object exists. 
By creating an object, you're effectively telling the Kubernetes system what 
you want your cluster's workload to look like; this is your cluster's *desired state*.

To work with Kubernetes objects - whether to create, modify, or delete them - 
you'll need to use the [Kubernetes API](/docs/concepts/overview/kubernetes-api/).
When you use the `kubectl` command-line interface, for example, 
the CLI makes the necessary Kubernetes API calls for you. 
You can also use the Kubernetes API directly in your own programs using 
one of the [Client Libraries](/docs/reference/using-api/client-libraries/).
-->
Kubernetes 对象是“目标性记录” —— 一旦创建该对象，Kubernetes 系统将不断工作以确保该对象存在。
通过创建对象，你就是在告知 Kubernetes 系统，你想要的集群工作负载状态看起来应是什么样子的，
这就是 Kubernetes 集群所谓的 **期望状态（Desired State）**。

操作 Kubernetes 对象 —— 无论是创建、修改或者删除 —— 需要使用
[Kubernetes API](/zh-cn/docs/concepts/overview/kubernetes-api)。
比如，当使用 `kubectl` 命令行接口（CLI）时，CLI 会调用必要的 Kubernetes API；
也可以在程序中使用[客户端库](/zh-cn/docs/reference/using-api/client-libraries/)，
来直接调用 Kubernetes API。

<!--
### Object Spec and Status

Almost every Kubernetes object includes two nested object fields that govern
the object's configuration: the object *`spec`* and the object *`status`*.
For objects that have a `spec`, you have to set this when you create the object,
providing a description of the characteristics you want the resource to have:
its _desired state_.
-->
### 对象规约（Spec）与状态（Status）    {#object-spec-and-status}

几乎每个 Kubernetes 对象包含两个嵌套的对象字段，它们负责管理对象的配置：
对象 **`spec`（规约）** 和 对象 **`status`（状态）**。
对于具有 `spec` 的对象，你必须在创建对象时设置其内容，描述你希望对象所具有的特征：
**期望状态（Desired State）**。

<!--
The `status` describes the _current state_ of the object, supplied and updated
by the Kubernetes system and its components. The Kubernetes
{{< glossary_tooltip text="control plane" term_id="control-plane" >}} continually
and actively manages every object's actual state to match the desired state you
supplied.
-->
`status` 描述了对象的**当前状态（Current State）**，它是由 Kubernetes 系统和组件设置并更新的。
在任何时刻，Kubernetes {{< glossary_tooltip text="控制平面" term_id="control-plane" >}}
都一直都在积极地管理着对象的实际状态，以使之达成期望状态。

<!--
For example: in Kubernetes, a Deployment is an object that can represent an
application running on your cluster. When you create the Deployment, you
might set the Deployment `spec` to specify that you want three replicas of
the application to be running. The Kubernetes system reads the Deployment
spec and starts three instances of your desired application-updating
the status to match your spec. If any of those instances should fail
(a status change), the Kubernetes system responds to the difference
between spec and status by making a correction-in this case, starting
a replacement instance.
-->
例如，Kubernetes 中的 Deployment 对象能够表示运行在集群中的应用。
当创建 Deployment 时，可能会去设置 Deployment 的 `spec`，以指定该应用要有 3 个副本运行。
Kubernetes 系统读取 Deployment 的 `spec`，
并启动我们所期望的应用的 3 个实例 —— 更新状态以与规约相匹配。
如果这些实例中有的失败了（一种状态变更），Kubernetes 系统会通过执行修正操作来响应
`spec` 和状态间的不一致 —— 意味着它会启动一个新的实例来替换。

<!--
For more information on the object spec, status, and metadata, see the 
[Kubernetes API Conventions](https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md).
-->
关于对象 spec、status 和 metadata 的更多信息，可参阅
[Kubernetes API 约定](https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md)。

<!--
### Describing a Kubernetes Object

When you create an object in Kubernetes, you must provide the object spec that describes its
desired state, as well as some basic information about the object (such as a name). When you use
the Kubernetes API to create the object (either directly or via `kubectl`), that API request must
include that information as JSON in the request body. **Most often, you provide the information to
`kubectl` in a .yaml file.** `kubectl` converts the information to JSON when making the API
request.


Here's an example `.yaml` file that shows the required fields and object spec for a Kubernetes Deployment:
-->
### 描述 Kubernetes 对象    {#describing-a-kubernetes-object}

创建 Kubernetes 对象时，必须提供对象的 `spec`，用来描述该对象的期望状态，
以及关于对象的一些基本信息（例如名称）。
当使用 Kubernetes API 创建对象时（直接创建，或经由 `kubectl`），
API 请求必须在请求本体中包含 JSON 格式的信息。
**大多数情况下，你需要提供 `.yaml` 文件为 kubectl 提供这些信息**。
`kubectl` 在发起 API 请求时，将这些信息转换成 JSON 格式。

这里有一个 `.yaml` 示例文件，展示了 Kubernetes Deployment 的必需字段和对象 `spec`：

{{< codenew file="application/deployment.yaml" >}}

<!--
One way to create a Deployment using a `.yaml` file like the one above is to use the
[`kubectl apply`](/docs/reference/generated/kubectl/kubectl-commands#apply) command
in the `kubectl` command-line interface, passing the `.yaml` file as an argument. Here's an example:
-->
相较于上面使用 `.yaml` 文件来创建 Deployment，另一种类似的方式是使用 `kubectl` 命令行接口（CLI）中的
[`kubectl apply`](/docs/reference/generated/kubectl/kubectl-commands#apply) 命令，
将 `.yaml` 文件作为参数。下面是一个示例：

```shell
kubectl apply -f https://k8s.io/examples/application/deployment.yaml
```

<!--
The output is similar to this:
-->
输出类似下面这样：

```
deployment.apps/nginx-deployment created
```

<!--
### Required Fields

In the `.yaml` file for the Kubernetes object you want to create, you'll need to set values for the following fields:

* `apiVersion` - Which version of the Kubernetes API you're using to create this object
* `kind` - What kind of object you want to create
* `metadata` - Data that helps uniquely identify the object, including a `name` string, `UID`, and optional `namespace`
* `spec` - What state you desire for the object
-->
### 必需字段    {#required-fields}

在想要创建的 Kubernetes 对象所对应的 `.yaml` 文件中，需要配置的字段如下：

* `apiVersion` - 创建该对象所使用的 Kubernetes API 的版本
* `kind` - 想要创建的对象的类别
* `metadata` - 帮助唯一标识对象的一些数据，包括一个 `name` 字符串、`UID` 和可选的 `namespace`
* `spec` - 你所期望的该对象的状态

<!--
The precise format of the object `spec` is different for every Kubernetes object, and contains
nested fields specific to that object. The [Kubernetes API Reference](/docs/reference/kubernetes-api/)
can help you find the spec format for all of the objects you can create using Kubernetes.
-->
对每个 Kubernetes 对象而言，其 `spec` 之精确格式都是不同的，包含了特定于该对象的嵌套字段。
我们能在 [Kubernetes API 参考](/zh-cn/docs/reference/kubernetes-api/)
找到我们想要在 Kubernetes 上创建的任何对象的规约格式。

<!--
For example, see the [`spec` field](/docs/reference/kubernetes-api/workload-resources/pod-v1/#PodSpec)
for the Pod API reference.
For each Pod, the `.spec` field specifies the pod and its desired state (such as the container image name for
each container within that pod).
Another example of an object specification is the
[`spec` field](/docs/reference/kubernetes-api/workload-resources/stateful-set-v1/#StatefulSetSpec)
for the StatefulSet API. For StatefulSet, the `.spec` field specifies the StatefulSet and
its desired state.
Within the `.spec` of a StatefulSet is a [template](/docs/concepts/workloads/pods/#pod-templates)
for Pod objects. That template describes Pods that the StatefulSet controller will create in order to
satisfy the StatefulSet specification.
Different kinds of object can also have different `.status`; again, the API reference pages
detail the structure of that `.status` field, and its content for each different type of object.
-->
例如，参阅 Pod API 参考文档中
[`spec` 字段](/zh-cn/docs/reference/kubernetes-api/workload-resources/pod-v1/#PodSpec)。
对于每个 Pod，其 `.spec` 字段设置了 Pod 及其期望状态（例如 Pod 中每个容器的容器镜像名称）。
另一个对象规约的例子是 StatefulSet API 中的
[`spec` 字段](/zh-cn/docs/reference/kubernetes-api/workload-resources/stateful-set-v1/#StatefulSetSpec)。
对于 StatefulSet 而言，其 `.spec` 字段设置了 StatefulSet 及其期望状态。
在 StatefulSet 的 `.spec` 内，有一个为 Pod 对象提供的[模板](/zh-cn/docs/concepts/workloads/pods/#pod-templates)。
该模板描述了 StatefulSet 控制器为了满足 StatefulSet 规约而要创建的 Pod。
不同类型的对象可以由不同的 `.status` 信息。API 参考页面给出了 `.status` 字段的详细结构，
以及针对不同类型 API 对象的具体内容。

## {{% heading "whatsnext" %}}

<!--
* Learn about the most important basic Kubernetes objects, such as [Pod](/docs/concepts/workloads/pods/).
* Learn about [controllers](/docs/concepts/architecture/controller/) in Kubernetes.
* [Using the Kubernetes API](/docs/reference/using-api/) explains some more API concepts.
-->
* 了解最重要的 Kubernetes 基本对象，例如 [Pod](/zh-cn/docs/concepts/workloads/pods/)。
* 了解 Kubernetes 中的[控制器](/zh-cn/docs/concepts/architecture/controller/)。
* [使用 Kubernetes API](/zh-cn/docs/reference/using-api/) 一节解释了一些 API 概念。