Docker 与 K8S学习笔记（二十二）—— 高效使用kubectl的小技巧

kubectl作为我们主要的操作K8S的工具，其具备非常丰富的功能，但是如果不经过打磨，使用起来还是存在诸多不便，今天我们来看看如何将我们的kubectl打磨的更加易用。

一、命令自动补全

kubectl中提供非常多的命令，如果每一次都要手动一个字符一个字符的敲未免太累了，那么如何配置自动补全呢？这里以ubuntu系统为例：

1、安装auto-completion工具

$ sudo apt update
Hit:1 http://archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:4 https://download.docker.com/linux/ubuntu bionic InRelease
Hit:5 http://archive.ubuntu.com/ubuntu bionic-backports InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
144 packages can be upgraded. Run 'apt list --upgradable' to see them.
$ sudo apt install bash-completion
Reading package lists... Done
Building dependency tree
Reading state information... Done
bash-completion is already the newest version (1:2.8-1ubuntu1).
0 upgraded, 0 newly installed, 0 to remove and 144 not upgraded.

PS：如果是centos系统，则使用yum install bash-completion -y命令安装

2、配置自动补全

Bash：

source <(kubectl completion bash)
echo "source <(kubectl completion bash)" >> ~/.bashrc

Zsh：

source <(kubectl completion zsh)
echo "[[ $commands[kubectl] ]] && source <(kubectl completion zsh)" >> ~/.zshrc

配置后就可以通过Tab键自动补全命令啦！

二、配置kubectl别名

我们可以通过设置别名简化kubectl命令，编辑.bashrc文件，添加如下内容：

alias sudo='sudo '
alias k='kubectl'
alias ka='kubectl apply --recursive -f'
alias kex='kubectl exec -i -t'
alias klo='kubectl logs -f'
alias kg='kubectl get'
alias kd='kubectl describe'

PS：alias sudo是为了解决sudo下别名不可用问题

保存后记得执行 source ~/.bashrc哈，接着我们体验下：

$ sudo ka webapp_pod.yaml
pod/webapp created
$ sudo kg pods
NAME     READY   STATUS              RESTARTS   AGE
webapp   0/2     ContainerCreating   0          7s
$ sudo kd pod webapp
Name:         webapp
Namespace:    default
Priority:     0
Node:         ayato/172.16.194.135
Start Time:   Wed, 09 Feb 2022 14:04:44 +0000
Labels:       app=webapp
Annotations:  <none>
Status:       Running
IP:           172.17.0.6
IPs:
  IP:  172.17.0.6
Containers:
  webapp:
    Container ID:   docker://d9ddf9dd47de12b53f2119bf75df6706bee2e7711509638ad52adc9addeda704
    Image:          172.16.194.135:5000/webapp:1.0
    Image ID:       docker-pullable://172.16.194.135:5000/webapp@sha256:df3a447a013ada0642dec67bb31976f42f1a0699a68873d0452f514fa24e5c77
    Port:           5000/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 09 Feb 2022 14:04:46 +0000
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /tmp from webapp-logs (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-pcr2h (ro)
  busybox:
    Container ID:  docker://6a6a35a628a782fc643af3dd49986bbc77c23de1ae4726bc521c77f61abbbf5d
    Image:         busybox
    Image ID:      docker-pullable://busybox@sha256:afcc7f1ac1b49db317a7196c902e61c6c3c4607d63599ee1a82d702d249a0ccb
    Port:          <none>
    Host Port:     <none>
    Command:
      sh
      -c
      tail -f /logs/log.out
    State:          Running
      Started:      Wed, 09 Feb 2022 14:06:53 +0000
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /logs from webapp-logs (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-pcr2h (ro)
Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True
  PodScheduled      True
Volumes:
  webapp-logs:
    Type:       EmptyDir (a temporary directory that shares a pod's lifetime)
    Medium:
    SizeLimit:  <unset>
  default-token-pcr2h:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-pcr2h
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                 node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age    From               Message
  ----    ------     ----   ----               -------
  Normal  Scheduled  2m23s  default-scheduler  Successfully assigned default/webapp to ayato
  Normal  Pulled     2m22s  kubelet            Container image "172.16.194.135:5000/webapp:1.0" already present on machine
  Normal  Created    2m21s  kubelet            Created container webapp
  Normal  Started    2m21s  kubelet            Started container webapp
  Normal  Pulling    2m21s  kubelet            Pulling image "busybox"
  Normal  Pulled     15s    kubelet            Successfully pulled image "busybox" in 14.633078305s
  Normal  Created    15s    kubelet            Created container busybox
  Normal  Started    14s    kubelet            Started container busybox

真的是飞一般的感觉！！！

三、Context和Namespace切换

我们在公司的容器平台上使用kubectl时，经常需要切换context和namespace，导致命令非常繁琐，那有没有简便的方式呢？—— kubectx

kubectx安装

$ sudo git clone https://github.com/ahmetb/kubectx /opt/kubectx
Cloning into '/opt/kubectx'...
remote: Enumerating objects: 1457, done.
remote: Counting objects: 100% (172/172), done.
remote: Compressing objects: 100% (115/115), done.
remote: Total 1457 (delta 85), reused 97 (delta 51), pack-reused 1285
Receiving objects: 100% (1457/1457), 905.30 KiB | 69.00 KiB/s, done.
Resolving deltas: 100% (817/817), done.
$ sudo ln -s /opt/kubectx/kubens /usr/local/bin/kubectl-ns
$ sudo ln -s /opt/kubectx/kubectx /usr/local/bin/kubectl-ctx

我们来看一下效果：

$ sudo k ctx
minikube
$ sudo k ctx minikube
Switched to context "minikube".
$ sudo k ns
default
kube-node-lease
kube-public
kube-system
kubernetes-dashboard
$ sudo k ns kube-public
Context "minikube" modified.
Active namespace is "kube-public".
$ sudo k ns default
Context "minikube" modified.
Active namespace is "default".

四、跟踪查看多个Pod的日志

我们一般使用kubectl logs命令查看Pod日志，但是它不能通过-f参数同时跟踪查看多个Pod日志，这就不方便了，毕竟实际生产环境中每个服务都会有多个Pod，这时我们可以使用stern这个工具，它具备如下能力：

• 允许使用正则表达式来选择需要查看的PodName

• 为不同 Pod 的日志展示不同的颜色

• 跟踪日志过程中假如有符合规则的新 Pod 被创建, 那么会自动添加到输出中

首先安装stern（下载stern时可能较慢可以多试几次）：

wget https://github.com/wercker/stern/releases/download/1.11.0/stern_linux_amd64
sudo mv stern_linux_amd64 /usr/local/bin/kubectl-tail
sudo chomd +x /usr/local/bin/kubectl-tail

安装完毕后让我一起感受一下stern的魅力吧，我的Pod里面有两个容器：webapp和busybox，如果使用kubectl logs 还得指定具体的容器，而使用stern就没有这样的限制。

$ sudo k tail .
+ webapp › busybox
+ webapp › webapp
webapp busybox 14:04:53.197 [INFO ] [main] [org.apache.coyote.http11.Http11NioProtocol] Initializing ProtocolHandler ["http-nio-4567"]
webapp busybox 14:04:53.200 [INFO ] [main] [org.apache.catalina.core.StandardService] Starting service [Tomcat]
webapp busybox 14:04:53.201 [INFO ] [main] [org.apache.catalina.core.StandardEngine] Starting Servlet engine: [Apache Tomcat/9.0.41]
webapp busybox 14:04:53.324 [INFO ] [main] [org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/]] Initializing Spring embedded WebApplicationContext
webapp busybox 14:04:53.325 [INFO ] [main] [org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext] Root WebApplicationContext: initialization completed in 2952 ms
webapp busybox 14:04:53.801 [INFO ] [main] [org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor] Initializing ExecutorService 'applicationTaskExecutor'
webapp busybox 14:04:54.264 [WARN ] [main] [org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration$DefaultTemplateResolverConfiguration] Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)
webapp busybox 14:04:54.377 [INFO ] [main] [org.apache.coyote.http11.Http11NioProtocol] Starting ProtocolHandler ["http-nio-4567"]
webapp busybox 14:04:54.481 [INFO ] [main] [org.springframework.boot.web.embedded.tomcat.TomcatWebServer] Tomcat started on port(s): 4567 (http) with context path ''
webapp busybox 14:04:54.509 [INFO ] [main] [org.demo.webapp.todolist.TodoListApplication] Started TodoListApplication in 6.235 seconds (JVM running for 8.074)
webapp webapp
webapp webapp   .   ____          _            __ _ _
webapp webapp  /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
webapp webapp ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
webapp webapp  \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
webapp webapp   '  |____| .__|_| |_|_| |_\__, | / / / /
webapp webapp  =========|_|==============|___/=/_/_/_/
webapp webapp  :: Spring Boot ::                (v2.4.2)
webapp webapp
webapp webapp 14:04:50.124 [INFO ] [main] [org.demo.webapp.todolist.TodoListApplication] Starting TodoListApplication v1.0-SNAPSHOT using Java 1.8.0_111 on webapp with PID 1 (/opt/soft/webapp.jar started by root in /opt/soft)
webapp webapp 14:04:50.165 [INFO ] [main] [org.demo.webapp.todolist.TodoListApplication] No active profile set, falling back to default profiles: default
webapp webapp 14:04:53.158 [INFO ] [main] [org.springframework.boot.web.embedded.tomcat.TomcatWebServer] Tomcat initialized with port(s): 4567 (http)
webapp webapp 14:04:53.197 [INFO ] [main] [org.apache.coyote.http11.Http11NioProtocol] Initializing ProtocolHandler ["http-nio-4567"]
webapp webapp 14:04:53.200 [INFO ] [main] [org.apache.catalina.core.StandardService] Starting service [Tomcat]
webapp webapp 14:04:53.201 [INFO ] [main] [org.apache.catalina.core.StandardEngine] Starting Servlet engine: [Apache Tomcat/9.0.41]
webapp webapp 14:04:53.324 [INFO ] [main] [org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/]] Initializing Spring embedded WebApplicationContext
webapp webapp 14:04:53.325 [INFO ] [main] [org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext] Root WebApplicationContext: initialization completed in 2952 ms
webapp webapp 14:04:53.801 [INFO ] [main] [org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor] Initializing ExecutorService 'applicationTaskExecutor'
webapp webapp 14:04:54.264 [WARN ] [main] [org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration$DefaultTemplateResolverConfiguration] Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)
webapp webapp 14:04:54.377 [INFO ] [main] [org.apache.coyote.http11.Http11NioProtocol] Starting ProtocolHandler ["http-nio-4567"]
webapp webapp 14:04:54.481 [INFO ] [main] [org.springframework.boot.web.embedded.tomcat.TomcatWebServer] Tomcat started on port(s): 4567 (http) with context path ''
webapp webapp 14:04:54.509 [INFO ] [main] [org.demo.webapp.todolist.TodoListApplication] Started TodoListApplication in 6.235 seconds (JVM running for 8.074)