When upgrading controlplane nodes, upgrading the kubelets should be done
as the last step after "kubeadm upgrade" was run on all of the control
plane nodes already.
Also apply consistency related cleanup to sections and section names.
lose apt-mark unhold kubectl when apt-get install kubectl. If not unhold kubectl, it would return the error follows:
``` shell
root@ecs-k8s-master:~# apt-mark unhold kubelet && apt-get update && apt-get install -y kubelet=1.15.0-00 kubectl=1.15.0-00 && apt-mark hold kubelet
kubelet was already not hold.
Hit:1 https://download.docker.com/linux/ubuntu xenial InRelease
Hit:2 https://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial InRelease
Hit:3 https://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-updates InRelease
Get:4 https://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-backports InRelease [107 kB]
Hit:4 https://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-backports InRelease
Hit:5 https://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-security InRelease
Hit:6 https://packages.cloud.google.com/apt kubernetes-xenial InRelease
Reading package lists... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
linux-headers-4.4.0-145 linux-headers-4.4.0-145-generic linux-image-4.4.0-145-generic linux-modules-4.4.0-145-generic
Use 'apt autoremove' to remove them.
The following held packages will be changed:
kubectl
The following packages will be upgraded:
kubectl kubelet
2 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.
E: Held packages were changed and -y was used without --allow-change-held-packages.
```
Lubomir I. Ivanov