k8s

Kubernetes-记录CKA认证

关于CKA考试的考试大纲，在GitHub上cncf/curriculum的仓库中有最新的说明，例如目前是：CKA_Curriculum_v1.34.pdf

linuxfoundation考试报名的页面的Domains & Competencies部分也说明了考试的能力知识要求。也给出了Learning Path to Certification，不过这个学习路径里面很多还是要付费的，还是算了...

在Youtube上发现了一个可以熟悉CKA考试流程的模式网站

https://killercoda.com/

bash
kubectl run nginx --image=nginx --dry-run=client -o yaml > pod.yaml

通过kubectl completion可以自动补全相关命令以及资源名称

bash
source <(kubectl completion zsh)  # set up autocomplete in zsh into the current shell
echo '[[ $commands[kubectl] ]] && source <(kubectl completion zsh)' >> ~/.zshrc # add autocomplete permanently to your zsh shell

kubectl completion <shell>（如 bash 或 zsh）会生成一段 Shell 脚本，这段脚本定义了：

  • 当你在终端输入 kubectl 并按 Tab 时，应该调用什么函数来生成补全建议；
  • 这些函数内部会：
    • 解析当前命令行上下文（比如你已经输入了 kubectl get po）；
    • 调用 kubectl 本身的内部逻辑（或 API） 获取可用的资源列表（如 Pod 名称、命名空间等）；
    • 将结果返回给 Shell，由 Shell 显示在终端上。

CKA考试期间需要辩解YAML文件，设置VIM的如下配置对于编辑YAML文件很有帮助：

bash
# ~/.vimrc
set expandtab # 用空格替换tab
set ts=2	# tab对应的空格的长度
set sw=2	# 缩进宽度
set autoindent # 自动缩进

Apiserver Crash

Misconfigure ETCD connectionChange the existing Apiserver manifest argument to: --etcd-servers=this-is-very-wrong .

Check what the logs say, without using anything in /var .

Fix the Apiserver again.

Log Locations Log locations to check:

  • /var/log/pods
  • /var/log/containers
  • crictl ps + crictl logs
  • docker ps + docker logs (in case when Docker is used)
  • kubelet logs: /var/log/syslog or journalctl

Solution

text
# always make a backup ! 
cp /etc/kubernetes/manifests/kube-apiserver.yaml ~/kube-apiserver.yaml.ori 

# make the change 
vim /etc/kubernetes/manifests/kube-apiserver.yaml 

# wait till container restarts 
watch crictl ps 

# check for apiserver pod 
k -n kube-system get pod

Apiserver is not coming back, we messed up!

bash
# 1) if we would check the /var directory 
cat /var/log/pods/kube-system_kube-apiserver-controlplane_e24b3821e9bdc47a91209bfb04056993/kube-apiserver/X.log 
> Err: connection error: desc = "transport: Error while dialing dial tcp: address this-is-very-wrong: missing port in address". Reconnecting... 

# 2) but here we want to find other ways, so we check the container logs 
crictl ps # maybe run a few times, because the apiserver container get's restarted 
crictl logs f669a6f3afda2 
> Error while dialing dial tcp: address this-is-very-wrong: missing port in address. Reconnecting... 

# 3) what about syslogs 
journalctl | grep apiserver # nothing specific 
cat /var/log/syslog | grep apiserver # nothing specific

Now undo the change and continue

bash
# smart people use a backup 
cp ~/kube-apiserver.yaml.ori /etc/kubernetes/manifests/kube-apiserver.yaml

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