Kubernetes的Deployment可以轻松地进行滚动更新，但是如果出现了问题，可能需要回滚到之前的版本。Deployment提供了回滚功能，可以让我们轻松地回滚到之前的版本。

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回滚Deployment

Deployment的回滚功能使用kubectl rollout undo命令来实现，我们可以使用以下命令回滚到上一次成功的版本：

kubectl rollout undo deployment/nginx-deployment

这将回滚到上一次成功的版本，如果没有成功的版本，则回滚到当前版本之前的版本。

我们还可以使用以下命令回滚到特定的版本：

kubectl rollout undo deployment/nginx-deployment --to-revision=2

这将回滚到指定的版本，版本号为2。

回滚操作会在后台进行，我们可以使用以下命令来查看回滚进度：

kubectl rollout status deployment/nginx-deployment

这会输出类似于以下内容的信息：

Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...deployment "nginx-deployment" successfully rolled out

这表示回滚正在进行中，需要等待一段时间才能完成。

当回滚操作完成后，我们可以使用以下命令查看Deployment的更新历史记录：

kubectl rollout history deployment/nginx-deployment

这将输出类似于以下内容的信息：

deployment.apps/nginx-deployment REVISION  CHANGE-CAUSE2         kubectl set image deployment/nginx-deployment nginx=nginx:1.17 --record=true3         kubectl set image deployment/nginx-deployment nginx=nginx:1.16 --record=true

我们可以看到Deployment已经回滚到了第2个版本，更新历史记录中显示了回滚操作。