DEV Community

Cover image for Add Taints To AWS EKS Cluster And Trouble Shooting
🚀 Vu Dao 🚀
🚀 Vu Dao 🚀

Posted on • Edited on

Add Taints To AWS EKS Cluster And Trouble Shooting

#aws #eks #k8s #systemd

Taints and Tolerations is used to ensure the node should not accept any pods that do not tolerate the taints. How to add taints to AWS EKS node group? This blog will show you how and the way of trouble shooting

Taints and Tolerations

What’s In This Document

🚀 How to taint eks node group

  • Use BootstrapArguments in Parameters of cloudformation to input to kubelet arguments Alt-Text

🚀 Understand kubelet systemd service in the eks node

  • Enter to the worker and Check kubelet status. We see that kubelet service is started with option --register-with-taints=dedicated=test:NoSchedule which is input from /etc/systemd/system/kubelet.service.d/30-kubelet-extra-args.conf.
 [root@ip-17-1-5-1 ec2-user]# systemctl status kubelet -l ● kubelet.service - Kubernetes Kubelet Loaded: loaded (/etc/systemd/system/kubelet.service; enabled; vendor preset: disabled) Drop-In: /etc/systemd/system/kubelet.service.d └─10-kubelet-args.conf, 30-kubelet-extra-args.conf Active: active (running) since Tue 2021-05-11 07:20:42 UTC; 1h 2min ago Docs: https://github.com/kubernetes/kubernetes Process: 4128 ExecStartPre=/sbin/iptables -P FORWARD ACCEPT -w 5 (code=exited, status=0/SUCCESS) Main PID: 4139 (kubelet) Tasks: 16 Memory: 141.5M CGroup: /system.slice/kubelet.service └─4139 /usr/bin/kubelet --cloud-provider aws --config /etc/kubernetes/kubelet/kubelet-config.json --kubeconfig /var/lib/kubelet/kubeconfig --container-runtime docker --network-plugin cni --node-ip=17.1.5.1 --pod-infra-container-image=0123456789012.dkr.ecr.ap-northeast-1.amazonaws.com/eks/pause:3.1-eksbuild.1 --node-labels=role=test --register-with-taints=dedicated=test:NoSchedule
Enter fullscreen mode Exit fullscreen mode 
 [root@ip-17-1-5-1 ec2-user]# cat /etc/systemd/system/kubelet.service.d/30-kubelet-extra-args.conf [Service] Environment='KUBELET_EXTRA_ARGS=--node-labels=role=test --register-with-taints=dedicated=test:NoSchedule'
Enter fullscreen mode Exit fullscreen mode
  • The 30-kubelet-extra-args.conf file is created by /etc/eks/bootstrap.sh 
 if [[ -n "$KUBELET_EXTRA_ARGS" ]]; then cat <<EOF > /etc/systemd/system/kubelet.service.d/30-kubelet-extra-args.conf [Service] Environment='KUBELET_EXTRA_ARGS=$KUBELET_EXTRA_ARGS' EOF fi
Enter fullscreen mode Exit fullscreen mode
  • Check the /var/log/messages to understand how systemD start the kubelet service.
 May 11 07:20:40 ip-17-1-5-1 systemd: Started Apply the settings specified in cloud-config. May 11 07:20:40 ip-17-1-5-1 systemd: Starting Execute cloud user/final scripts... May 11 07:20:40 ip-17-1-5-1 cloud-init: Cloud-init v. 19.3-3.amzn2 running 'modules:final' at Tue, 11 May 2021 07:20:40 +0000. Up 28.99 seconds. May 11 07:20:40 ip-17-1-5-1 cloud-init: + /etc/eks/bootstrap.sh eks-cluster --kubelet-extra-args '--node-labels=role=test --register-with-taints=dedicated=test:NoSchedule' May 11 07:20:40 ip-17-1-5-1 cloud-init: % Total % Received % Xferd Average Speed Time Time Time Current May 11 07:20:40 ip-17-1-5-1 cloud-init: Dload Upload Total Spent Left Speed May 11 07:20:40 ip-17-1-5-1 cloud-init: 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0#015100 56 100 56 0 0 5600 0 --:--:-- --:--:-- --:--:-- 5600 May 11 07:20:41 ip-17-1-5-1 dhclient[2969]: XMT: Solicit on eth0, interval 15840ms. May 11 07:20:42 ip-17-1-5-1 systemd: Reloading. May 11 07:20:42 ip-17-1-5-1 systemd: Reloading. May 11 07:20:42 ip-17-1-5-1 cloud-init: Created symlink from /etc/systemd/system/multi-user.target.wants/kubelet.service to /etc/systemd/system/kubelet.service. May 11 07:20:42 ip-17-1-5-1 systemd: Starting Kubernetes Kubelet... May 11 07:20:42 ip-17-1-5-1 systemd: Started Kubernetes Kubelet. May 11 07:20:42 ip-17-1-5-1 cloud-init: + /opt/aws/bin/cfn-signal --exit-code 0 --stack eks-cluster-test --resource NodeGroup --region ap-northeast-1 May 11 07:20:42 ip-17-1-5-1 systemd: Started Kubernetes systemd probe. May 11 07:20:42 ip-17-1-5-1 systemd: Starting Kubernetes systemd probe. May 11 07:20:42 ip-17-1-5-1 kubelet: I0511 07:20:42.909859 4139 server.go:417] Version: v1.18.8-eks-7c9bda May 11 07:20:42 ip-17-1-5-1 kubelet: W0511 07:20:42.910542 4139 plugins.go:115] WARNING: aws built-in cloud provider is now deprecated. The AWS provider is deprecated and will be removed in a future release May 11 07:20:42 ip-17-1-5-1 kubelet: I0511 07:20:42.914985 4139 aws.go:1241] Zone not specified in configuration file; querying AWS metadata service May 11 07:20:42 ip-17-1-5-1 kubelet: I0511 07:20:42.919112 4139 aws.go:1281] Building AWS cloudprovider
Enter fullscreen mode Exit fullscreen mode
  • kubelet has dependency on cloud-init service which run /etc/eks/bootstrap.sh with args from cloudformation parameters.

🚀 Facing some issues

  • When apply taint for the eks node I met two issues: typo and missing double '

1. Typo which caused the bash script failed
Alt-Text

 May 11 04:38:50 ip-172-10-21-203 cloud-init: Cloud-init v. 19.3-3.amzn2 running 'modules:final' at Tue, 11 May 2021 04:38:50 +0000. Up 43.12 seconds. May 11 04:38:50 ip-172-10-21-203 cloud-init: /var/lib/cloud/instance/scripts/part-001: line 3: unexpected EOF while looking for matching {% raw %}`'' May 11 04:38:50 ip-172-10-21-203 cloud-init: /var/lib/cloud/instance/scripts/part-001: line 8: syntax error: unexpected end of file May 11 04:38:50 ip-172-10-21-203 cloud-init: May 11 04:38:50 cloud-init[4080]: util.py[WARNING]: Failed running /var/lib/cloud/instance/scripts/part-001 [2] ``` **2. Missing double `'`** - The `bootstrap.sh` get `KUBELET_EXTRA_ARGS` as second argument so for more than one option, all must be in double `'` ``` --kubelet-extra-args) KUBELET_EXTRA_ARGS=$2 ``` ### 🚀 **[Conclusion](#-Conclusion)** - Use combine of`node affinity`, `taints` and `toleration` to ensure the pod of specific service stays in correct node and prevent others. - When starting an EKS node (worker), it uses cloud-init service to run eks bootstrap script which helps to config the extra arguments of kubelet service to startup. - Using systemD services ensure the order of depenent services. --- <h3 align="center"> <a href="https://dev.to/vumdao">:stars: Blog</a> <span> · </span> <a href="https://github.com/vumdao/cdk8s-example">Github</a> <span> · </span> <a href="https://stackoverflow.com/users/11430272/vumdao">stackoverflow</a> <span> · </span> <a href="https://www.linkedin.com/in/vu-dao-9280ab43/">Linkedin</a> <span> · </span> <a href="https://www.linkedin.com/groups/12488649/">Group</a> <span> · </span> <a href="https://www.facebook.com/CloudOpz-104917804863956">Page</a> <span> · </span> <a href="https://twitter.com/VuDao81124667">Twitter :stars:</a> </h3>
Enter fullscreen mode Exit fullscreen mode

Top comments (0)