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geekpi
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[#]: subject: (Learn essential Kubernetes commands with a new cheat sheet)
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[#]: via: (https://opensource.com/article/21/5/kubernetes-cheat-sheet)
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[#]: author: (Seth Kenlon https://opensource.com/users/seth)
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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Learn essential Kubernetes commands with a new cheat sheet
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======
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Start exploring kubectl, containers, pods, and more, then download our
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free cheat sheet so you always have the key commands at your fingertips.
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![Cheat Sheet cover image][1]
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The cloud runs largely on Kubernetes, Kubernetes largely runs on Linux, and Linux runs best when it has a skilled sysadmin at the controls. Whether you consider yourself a cloud architect or just a humble sysadmin, the modern internet needs users who understand how applications and services can be created within containers, scaled on demand, and monitored and managed judiciously.
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One of the first steps into the brave world of containers is learning Kubernetes and its quintessential command: `kubectl`.
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### Installing kubectl
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The `kubectl` command allows you to run commands on Kubernetes clusters. You use `kubectl` to deploy applications, view logs, inspect and manage cluster resources, and troubleshoot issues when they arise. The classic "problem" with `kubectl` (and Kubernetes as a whole) is that to run commands against a cluster, you first need a cluster. However, there are easy solutions.
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First, you can create your own Kubernetes cluster for the cost of three Raspberry Pi boards and associated peripherals (power supplies, mostly). Once you've acquired the hardware, read Chris Collins' [_Build a Kubernetes cluster with the Raspberry Pi_][2], and you'll have your very own cluster with `kubectl` installed.
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The other way to acquire a cluster is to use [Minikube][3], a practice environment for Kubernetes. Of all the methods of getting a cluster up and running, this is the easiest.
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There are yet more options; for example, you can take a course on Kubernetes to gain access to a lab running a cluster, or you can buy time on a cloud. It doesn't matter how you gain access to a cluster, as long as you have a Kubernetes environment to practice on.
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Once you have access to a cluster, you can start exploring the `kubectl` command.
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### Understanding pods and containers
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A container is a lightweight, partial Linux system dedicated to running an application or service. A container is constrained by a [kernel namespace][4], which provides it access to vital system components on its host (the computer running the container) while preventing it from sending data out to its host. Containers are kept as container images (or just _images_ for short) and defined by text files called _Containerfiles_ or _Dockerfiles_.
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A pod is a formal collection of containers and an easy way for an administrator to scale, monitor, and maintain any number of containers.
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Together, these are like the "apps" of Kubernetes. Creating or acquiring container images is how you run services on the cloud.
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### Running a pod
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Two reliable registries of container images are Docker Hub and Quay. You can search a registry website for a list of available images. There are usually official images of large projects provided by the project, as well as community images for specialized, customized, or niche projects. One of the simplest and smallest images is a [BusyBox][5] container, which provides a minimal shell environment and some common commands.
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Whether you pull an image from a registry or write your own image definition and pull that into your cluster from a Git repository, the workflow is the same. When you want to start a pod in Kubernetes:
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1. Find an image you want to use on [Docker Hub][6] or [Quay][7]
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2. Pull the image
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3. Create a pod
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4. Deploy the pod
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If you want to use the example BusyBox container, you can do the last three steps in a single command:
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```
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`$ kubectl create deployment my-busybox --image=busybox`
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```
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Wait for kubectl to complete the process, and in the end, you have a running BusyBox instance. The pod isn't exposed to the rest of the world. It's just quietly running on your cluster in the background.
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To see what pods are running on your cluster:
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```
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`$ kubectl get pods --all-namespaces`
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```
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You can also get information about the pod deployment:
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```
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`$ kubectl describe deployment my-busybox`
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```
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### Interacting with a pod
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Containers usually contain configuration files that cause them to be automated. For instance, installing the Nginx httpd server as a container should not require your interaction. You start the container running, and it just works. This is true for the first container you add to a pod and for every container thereafter.
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One of the advantages of the Kubernetes model is that you can scale your services as needed. Should your web service become overwhelmed by unexpected traffic, you can start an identical container in your cloud (using the `scale` or `autoscale` subcommand), doubling your service's ability to handle incoming requests.
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Even so, sometimes it's nice to see some proof that a pod is running as expected or to be able to troubleshoot something that doesn't appear to be functioning correctly. For this, you can run arbitrary commands in a container:
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```
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`$ kubectl exec my-busybox -- echo "hello cloud"`
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```
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Alternately, you can open a shell in your container, piping your standard input into it and its output to your terminal's stdout:
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```
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`$ kubectl exec --stdin --tty my-busybox -- /bin/sh`
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```
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### Exposing services
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By default, pods aren't exposed to the outside world upon creation, giving you time to test and verify before going live. Assume you want to install and deploy the Nginx web server as a pod on your cluster and make it accessible. As with any service, you must point your pod to a port on your server. The `kubectl` subcommand `expose` can do this for you:
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```
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$ kubectl create deployment \
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my-nginx --image=nginx
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$ kubectl expose deployment \
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my-nginx --type=LoadBalancer --port=8080
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```
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As long as your cluster is accessible from the internet, you can test your new web server's accessibility by opening a browser and navigating to your public IP address.
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### More than just pods
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Kubernetes provides a lot more than just stock images of common services. In addition to being a system for [container orchestration][8], it's also a platform for cloud development. You can write and deploy applications, manage and monitor performance and traffic, implement intelligent load balancing strategies, and much more.
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Kubernetes is a powerful system, and it has quickly become the foundation for all kinds of clouds, most significantly the [open hybrid cloud][9]. Start learning Kubernetes today. And as you learn more about Kubernetes, you'll need some quick reminders of its main concepts and general syntax, so [**download our Kubernetes cheat sheet**][10] and keep it nearby.
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/21/5/kubernetes-cheat-sheet
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作者：[Seth Kenlon][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/seth
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/coverimage_cheat_sheet.png?itok=lYkNKieP (Cheat Sheet cover image)
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[2]: https://opensource.com/article/20/6/kubernetes-raspberry-pi
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[3]: https://opensource.com/article/18/10/getting-started-minikube
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[4]: https://opensource.com/article/19/10/namespaces-and-containers-linux
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[5]: https://www.busybox.net/
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[6]: http://hub.docker.com
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[7]: http://quay.io
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[8]: https://opensource.com/article/20/11/orchestration-vs-automation
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[9]: https://opensource.com/article/20/10/keep-cloud-open
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[10]: https://opensource.com/downloads/kubernetes-cheat-sheet
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@ -0,0 +1,137 @@
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[#]: subject: (Learn essential Kubernetes commands with a new cheat sheet)
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[#]: via: (https://opensource.com/article/21/5/kubernetes-cheat-sheet)
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[#]: author: (Seth Kenlon https://opensource.com/users/seth)
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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用新的速查表学习 Kubernetes 的基本命令
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======
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开始探索 kubectl、容器、pod 等，接着下载我们的免费的速查表，这样你就可以随时掌握关键的命令了。
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![Cheat Sheet cover image][1]
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云计算主要是在 Kubernetes 上运行，Kubernetes 主要是在 Linux 上运行，而 Linux 在有熟练的系统管理员控制时运行得最好。无论你认为自己是云计算架构师还是只是一个谦虚的系统管理员，现代互联网都需要了解如何在容器中创建应用和服务，按需扩展，按需扩展以及如何明智地进行监视和管理。
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进入勇敢的容器世界的第一步是学习 Kubernetes 和它的基本命令：`kubectl`。
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### 安装 kubectl
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`kubectl` 命令允许你在 Kubernetes 集群上运行命令。你使用 `kubectl` 来部署应用，查看日志，检查和管理集群资源，并在出现问题时进行故障排除。`kubectl`（以及整个 Kubernetes）的典型”问题“是，要对集群运行命令，你首先需要一个集群。然而，有一些简单的解决方案。
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首先，你可以创建自己的 Kubernetes 集群，只需买三块树莓派板和相关外围设备（主要是电源）。当你获得了硬件，阅读 Chris Collins 的[_使用树莓派构建 Kubernetes 集群_][2]，你就会拥有自己的安装有 `kubectl` 的集群。
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另一种获得集群的方法是使用 [Minikube][3]，这是一个 Kubernetes 的实践环境。在所有建立和运行集群的方法中，这是最简单的。
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还有更多的选择；例如，你可以参加一个关于 Kubernetes 的课程，以获得一个运行集群的实验室，或者你可以在云上购买时间。只要你有一个 Kubernetes 环境来练习，如何获得集群并不重要。
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当你你能访问一个集群，你就可以开始探索 `kubectl` 命令。
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### 了解 pod 和容器
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容器是一个轻量级的、部分的 Linux 系统，专门用于运行一个应用或服务。容器受到[内核命名空间][4]的限制，这使它能够访问其主机（运行容器的计算机）上的重要系统组件，同时防止它向其主机发送数据。容器以容器镜像（或简称_镜像_）的形式保存，并由称为 _Containerfiles_ 或 _Dockerfiles_ 的文本文件定义。
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一个 pod 是容器的正式集合，也是管理员扩展、监控和维护任何数量的容器的一种简单方法。
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这些一起就像 Kubernetes 的”应用“。创建或获取容器镜像是你在云上运行服务的方式。
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### 运行一个 pod
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容器镜像的两个可靠仓库是 Docker Hub 和 Quay。你可以在仓库中搜索可用的镜像列表。通常有由项目提供的大型项目的官方镜像，也有专门的、定制的或特殊项目的社区镜像。最简单和最小的镜像之一是 [BusyBox][5] 容器，它提供了一个最小的 shell 环境和一些常用命令。
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无论你是从仓库中拉取镜像，还是自己编写镜像定义并从 Git 仓库中拉取到集群中，其工作流程都是一样的。当你想在 Kubernetes 中启动一个 pod 时：
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1. 在 [Docker Hub][6] 或 [Quay][7] 上找到一个你想使用的镜像
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2. 拉取镜像
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3. 创建一个 pod
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4. 部署 pod
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如果你想使用 BusyBox 容器的例子，你可以用一条命令完成最后三个步骤：
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```
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`$ kubectl create deployment my-busybox --image=busybox`
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```
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等待 kubectl 完成这个过程，最后你就有了一个正在运行的 BusyBox 实例。这个 pod 并没有暴露给其他人。它只是在后台安静地在你的集群上运行。
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要看你的集群上有哪些 pod 在运行：
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```
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`$ kubectl get pods --all-namespaces`
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```
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你也可以获得关于 pod 部署的信息：
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```
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`$ kubectl describe deployment my-busybox`
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```
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### 与 pod 互动
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容器通常包含使其自动化的配置文件。例如，将 Nginx httpd 服务器作为容器安装，应该不需要你的互动。你开始运行容器，它就会工作。对于你添加到 pod 中的第一个容器和之后的每个容器都是如此。
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Kubernetes 模型的优点之一是，你可以根据需要扩展你的服务。如果你的网络服务被意外的流量淹没，你可以在你的云中启动一个相同的容器（使用 `scale` 或 `autoscale` 子命令），使你的服务处理传入请求的能力增加一倍。
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即便如此，有时还是很高兴看到一些证明 pod 正在按预期运行的证据，或者能够对似乎无法正常运行的某些问题进行故障排除。为此，你可以在一个容器中运行任意的命令：
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```
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`$ kubectl exec my-busybox -- echo "hello cloud"`
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```
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另外，你可以在你的容器中打开一个 shell，用管道将你的标准输入输入到其中，并将其输出到终端的标准输出：
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```
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`$ kubectl exec --stdin --tty my-busybox -- /bin/sh`
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```
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### 暴露服务
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默认情况下，pod 在创建时不会暴露给外界，这样你就有时间在上线前进行测试和验证。假设你想把 Nginx Web 服务器作为一个 pod 安装和部署在你的集群上，并使其可以访问。与任何服务一样，你必须将你的 pod 指向服务器上的一个端口。`kubectl` 子命令 `expose` 可以为你做到这点：
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```
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$ kubectl create deployment \
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my-nginx --image=nginx
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$ kubectl expose deployment \
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my-nginx --type=LoadBalancer --port=8080
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```
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只要你的集群可以从互联网上访问，你就可以通过打开浏览器并导航到你的公共 IP 地址来测试你的新 Web 服务器的可访问性。
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### 不仅仅是 pod
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Kubernetes 提供了很多东西，而不仅仅是存储普通服务的镜像。除了作为一个[容器协调][8]的系统，它还是一个云开发的平台。你可以编写和部署应用，管理和监控性能和流量，实施智能负载平衡策略等。
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Kubernetes 是一个强大的系统，它已经迅速成为各种云的基础，最主要的是[开放混合云][9]。今天就开始学习 Kubernetes 吧。随着你对 Kubernetes 的进一步了解，你会需要一些关于其主要概念和一般语法的快速提醒，所以[**下载我们的 Kubernetes 速查表**][10]并将它放在身边。
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--------------------------------------------------------------------------------
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||||
via: https://opensource.com/article/21/5/kubernetes-cheat-sheet
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作者：[Seth Kenlon][a]
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选题：[lujun9972][b]
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译者：[geekpi](https://github.com/geekpi)
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||||
校对：[校对者ID](https://github.com/校对者ID)
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||||
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||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://opensource.com/users/seth
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/coverimage_cheat_sheet.png?itok=lYkNKieP (Cheat Sheet cover image)
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[2]: https://opensource.com/article/20/6/kubernetes-raspberry-pi
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[3]: https://opensource.com/article/18/10/getting-started-minikube
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[4]: https://opensource.com/article/19/10/namespaces-and-containers-linux
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[5]: https://www.busybox.net/
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[6]: http://hub.docker.com
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[7]: http://quay.io
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[8]: https://opensource.com/article/20/11/orchestration-vs-automation
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[9]: https://opensource.com/article/20/10/keep-cloud-open
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[10]: https://opensource.com/downloads/kubernetes-cheat-sheet
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