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

admin 发表于 2022-2-12 14:35:42

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
<div class="cnblogs_code">
<pre>$ 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.</pre>
</div>
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：
<div class="cnblogs_code">
<pre>source <(kubectl completion bash)
echo "source <(kubectl completion bash)" >> ~/.bashrc</pre>
</div>
Zsh：
<div class="cnblogs_code">
<pre>source <(kubectl completion zsh)
echo "[[ $commands ]] && source <(kubectl completion zsh)" >> ~/.zshrc</pre>
</div>
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：
<div class="cnblogs_code">
<pre>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'</pre>
</div>
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：
<div class="cnblogs_code">
<pre>$ 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
---- ------ ---- ---- -------
NormalScheduled2m23sdefault-schedulerSuccessfully assigned default/webapp to ayato
NormalPulled 2m22skubelet Container image "172.16.194.135:5000/webapp:1.0" already present on machine
NormalCreated 2m21skubelet Created container webapp
NormalStarted 2m21skubelet Started container webapp
NormalPulling 2m21skubelet Pulling image "busybox"
NormalPulled 15s kubelet Successfully pulled image "busybox" in 14.633078305s
NormalCreated 15s kubelet Created container busybox
NormalStarted 14s kubelet Started container busybox</pre>
</div>
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
<div class="cnblogs_code">
<pre>$ 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</pre>
</div>
我们来看一下效果：
<div class="cnblogs_code">
<pre>$ 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".</pre>
</div>
 
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：
<ul class="list-paddingleft-2">
<li>
允许使用正则表达式来选择需要查看的PodName
</li>
<li>
为不同 Pod 的日志展示不同的颜色
</li>
<li>
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
</li>
</ul>
首先安装stern（下载stern时可能较慢可以多试几次）：
<div class="cnblogs_code">
<pre>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</pre>
</div>
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。
<div class="cnblogs_code">
<pre>$ sudo k tail .
+ webapp › busybox
+ webapp › webapp
webapp busybox 14:04:53.197 Initializing ProtocolHandler ["http-nio-4567"]
webapp busybox 14:04:53.200 Starting service
webapp busybox 14:04:53.201 Starting Servlet engine:
webapp busybox 14:04:53.324 ..[/]] Initializing Spring embedded WebApplicationContext
webapp busybox 14:04:53.325 Root WebApplicationContext: initialization completed in 2952 ms
webapp busybox 14:04:53.801 Initializing ExecutorService 'applicationTaskExecutor'
webapp busybox 14:04:54.264 Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)
webapp busybox 14:04:54.377 Starting ProtocolHandler ["http-nio-4567"]
webapp busybox 14:04:54.481 Tomcat started on port(s): 4567 (http) with context path ''
webapp busybox 14:04:54.509 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 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 No active profile set, falling back to default profiles: default
webapp webapp 14:04:53.158 Tomcat initialized with port(s): 4567 (http)
webapp webapp 14:04:53.197 Initializing ProtocolHandler ["http-nio-4567"]
webapp webapp 14:04:53.200 Starting service
webapp webapp 14:04:53.201 Starting Servlet engine:
webapp webapp 14:04:53.324 ..[/]] Initializing Spring embedded WebApplicationContext
webapp webapp 14:04:53.325 Root WebApplicationContext: initialization completed in 2952 ms
webapp webapp 14:04:53.801 Initializing ExecutorService 'applicationTaskExecutor'
webapp webapp 14:04:54.264 Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)
webapp webapp 14:04:54.377 Starting ProtocolHandler ["http-nio-4567"]
webapp webapp 14:04:54.481 Tomcat started on port(s): 4567 (http) with context path ''
webapp webapp 14:04:54.509 Started TodoListApplication in 6.235 seconds (JVM running for 8.074)</pre>
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Docker 与 K8S学习笔记（二十二）—— 高效使用kubectl的小技巧