switchhosts没有写入权限

## 如何在K8S集群中实现"switchhosts没有写入权限"

欢迎来到Kubernetes（K8S）的世界！在K8S集群中，有时候我们需要限制某些用户或服务账号对系统的访问权限，比如禁止"switchhosts"命令写入权限。本文将介绍如何在K8S集群中实现这一目标。

### 一、实现步骤

以下是实现"switchhosts没有写入权限"的具体步骤：

| 步骤 | 操作 |
| ---- | ---- |
| 1 | 创建名为"no-write-hosts"的ServiceAccount |
| 2 | 创建名为"no-write-hosts"的ClusterRole |
| 3 | 将ClusterRole与ServiceAccount绑定 |
| 4 | 创建名为"no-write-hosts"的ClusterRoleBinding |
| 5 | 将ClusterRoleBinding与ServiceAccount绑定 |

### 二、操作指南

#### 1. 创建名为"no-write-hosts"的ServiceAccount

```bash
kubectl create sa no-write-hosts
```
这条命令创建一个名为"no-write-hosts"的ServiceAccount，用于代表具有访问Kubernetes API权限的服务账号。

#### 2. 创建名为"no-write-hosts"的ClusterRole

```bash
kubectl apply -f no-write-hosts-clusterrole.yaml
```
具体"no-write-hosts-clusterrole.yaml"文件内容如下：

```yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: no-write-hosts
rules:
- apiGroups: [""]
resources: ["configmaps"]
verbs: ["get", "list", "watch"]
```
该ClusterRole定义了对configmaps资源的操作权限，仅限于get、list和watch操作，不包含写入权限。

#### 3. 将ClusterRole与ServiceAccount绑定

```bash
kubectl create clusterrolebinding no-write-hosts-binding --clusterrole=no-write-hosts --serviceaccount=default:no-write-hosts
```
该命令将ClusterRole"no-write-hosts"与ServiceAccount"no-write-hosts"绑定，使ServiceAccount具有ClusterRole所定义的权限。

#### 4. 创建名为"no-write-hosts"的ClusterRoleBinding

```bash
kubectl apply -f no-write-hosts-clusterrolebinding.yaml
```
具体"no-write-hosts-clusterrolebinding.yaml"文件内容如下：

```yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: no-write-hosts-binding
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: no-write-hosts
subjects:
- kind: ServiceAccount
name: no-write-hosts
namespace: default
```
该ClusterRoleBinding将ClusterRole"no-write-hosts"绑定到ServiceAccount"no-write-hosts"，确保ServiceAccount能够继承相关权限。

#### 5. 将ClusterRoleBinding与ServiceAccount绑定

```bash
kubectl create clusterrolebinding no-write-hosts-binding --clusterrole=no-write-hosts --serviceaccount=default:no-write-hosts
```
最后，通过再次将ClusterRoleBinding与ServiceAccount绑定，以确保权限正常生效。

### 结语

通过以上操作，我们成功地限制了"switchhosts"命令的写入权限，保证了系统安全性。在Kubernetes中，RBAC（基于角色的访问控制）是一种强大的权限控制机制，可以帮助我们精确地管理用户或服务账号的权限，保护系统免受潜在的攻击。希望本文能帮助你理解如何在Kubernetes集群中实现权限控制，并能够灵活应用于实际开发中。