A Technical I.T./DevOps Blog
Question
What is a service mesh?
Answer
In the context of Kubernetes, it is something that “provides infrastructure services for traffic management, observability, and security” for container connectivity (as explained on page 230 of Kubernetes Patterns by Bilgin Ibryam and Roland Huß (O’Reilly). Copyright 2019 Bilgin Ibryam and Roland Huß, 978-1-492-05028-5). A service mesh will often use a sidecar.
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One of the following problems occurs:
Problem scenario #1
You run some systemctl commands to start the Docker service, but you get this error: “Failed to enable unit: Unit file docker.service does not exist.”
Or you run some other command and see this:
“Unit docker.service not found.”
What should you do to get the docker.service file on a RHEL 8.x server?
Problem scenario #2
You are running a kubeadm command on RHEL 8,
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Continue reading “How Do You Install the docker.service File on RHEL 8.x?”
Question
What is Envoy in Kubernetes?
Answer
“Originally built at Lyft, Envoy is a high performance C++ distributed proxy designed for single services and applications, as well as a communication bus and “universal data plane” designed for large microservice “service mesh” architectures. Built on the learnings of solutions such as NGINX, HAProxy, hardware load balancers, and cloud load balancers, Envoy runs alongside every application and abstracts the network by providing common features in a platform-agnostic manner.
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Problem scenario
When you run a kubectl rollout history deployment foobar command, the “CHANGE-CAUSE” is empty for certain rows (revision numbers). What can you do to keep this column with useful descriptions (or relevant commands)?
Possible Solution #1
Going forward, use the –record flag when running kubectl create [deployment] or kubectl set image deployment … commands.
Possible Solution #2
Manually edit the manifest of the resource in the deployment.
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Problem scenario
kubectl commands are failing with an error message like this: “Unable to connect to the server: dial tcp: lookup ABCD123EFG.gr7.us-west-1.eks.amazonaws.com on x.x.x.x:53: no such host”
How do you get kubectl commands to work?
Possible Solution #1
If you are using EKS and you have the name of the cluster (e.g., “foobar”), run a command like this:
aws eks update-kubeconfig –name foobar
Possible Solution #2
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Problem scenario
You run a kubectl command, but you receive one of the following error messages:
Warning FailedScheduling default-scheduler no nodes available to schedule pods
No resources found
What should you do?
Possible Solution #1
Did the control plane lose connectivity with the worker nodes? An intermediate network device such as a firewall may have been implemented.
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Problem scenario
In the AWS Management Console, you cannot add a Node to an EKS cluster. The “Node IAM Role” never has any option. You click the “refresh” arrow, but all you see is “No roles found. Follow the link above to create a new role.” What should you do?
Solution
1. Install and configure the AWS CLI. If you need assistance with this,
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Problem scenario
You want to configure the maximum number of Kubernetes readiness probe failures. How do you set this amount?
Solution
Use the failureThreshold setting.
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Continue reading “How Do You Configure the Kubernetes readiness Probe Max Failure Limit?”
Problem scenario
Your Kubernetes cluster is not working. The nodes are not ready. You see your Kubernetes nodes are not ready (with kubectl get nodes). You also see this error from a kubectl describe node foobar command:
runtime network not ready: NetworkReady=false reason:NetworkPluginNotReady message:docker: network plugin is not ready: cni config uninitialized
What should you do?
(If you get a different error,
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Continue reading “How Do You Get Kubernetes Nodes to Be Ready?”
Problem scenario
You want to know what CNI plugin your Kubernetes cluster is using (e.g., Flannel, Calico, Weave Net, Romana or another one). What do you do?
Possible solution
“You can install only one Pod network per cluster.” taken from Kubernetes.io.
Go to a worker node and run these commands and look at the output:
ls -lh /etc/cni/net.d
ls -lh /opt/cni/bin | grep -i flannel
ls -lh /opt/cni/bin | grep -i calico
Use the sudo find / -name command to search for Romana or Weavenet vestiges.
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