A Technical I.T./DevOps Blog
Question
You know cgroups provide isolation (along with namespaces in the context of containers). But what exactly are cgroups?
Answer
cgroups enforce hard limits of subsystems to allow efficient allocation of resources of the super-system.
Cgroups allow you to allocate resources — such as CPU time, system memory, network bandwidth, or combinations of these resources — among user-defined groups of tasks (processes) running on a system.
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Problem scenario
You have a Pod that you want to run on a worker node. Its status is “Pending.” What can you do to get the Pod to proceed (and what are some common root causes for this problem)?
Background
A common root cause is that the nodes have insufficient resources for the Pod (e.g., insufficient CPU or memory).
Possible Solution #1
Wait.
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Continue reading “Why is a Kubernetes Pod’s Status “Pending”, and What Can Be Done about It?”
Problem scenario
You want to pass more than one subnet to an “aws eks” command.
You tried to delimit the list with commas (or separate two subnet IDs with commas). You received this error message:
An error occurred (InvalidParameterException) when calling the CreateNodegroup operation: The subnet ID ‘subnet-0abcd1234,subnet-zyxw9876’ does not exist (Service: AmazonEC2; Status Code: 400; Error Code: InvalidSubnetID.NotFound; Request ID: Proxy: null)
What should you do?
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Continue reading “How Do You Pass Two or More Subnets to an “aws eks” Command?”
Problem scenario
You have a Docker container that supports Chef or some automatic way of installing Chef. The automation is failing at the end because you are being prompted to accept a license. What should you do to be able to invoke Chef commands automatically?
Solution
With the first Chef command, e.g., “chef env”, use the “–chef-license accept” option/flag. Here is an example:
chef env –chef-license accept
For more information,
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Problem scenario
The nodes in a Kubernetes cluster are not working. What should you do?
Possible Solution #1
Run this command: kubectl get nodes
For the node that is not healthy, assuming its hostname is called “foobar”, run this command: kubectl describe node foobar
Possible Solution #2
If you have pods and no nodes (which could be the case),
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Problem scenario
You want to list IAM roles that have access to EKS. You have the AWS CLI installed and jq installed. What should you do?
Solution
Run this command:
aws iam list-roles | jq -r ‘.Roles[] | select(.AssumeRolePolicyDocument.Statement[].Principal.Service==”eks.amazonaws.com”)’ …
Continue reading “What AWS CLI Command Can You Run to List Roles with EKS Access?”
Problem scenario
You are trying to run “kubeadm init”, but you get this error:
“failed with error: Get “http://localhost:10248/healthz”: dial tcp 127.0.0.1:10248: connect: connection refused.”
What should you do?
Solution
Is the kubelet service running? Run this: sudo systemctl status kubelet
To install the kubelet, see this posting for How Do You Install the kubelet on any type of Linux?
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Problem scenario
You are trying to run a kubeadm command. But you get this error:
[preflight] Running pre-flight checks
error execution phase preflight: [preflight] Some fatal errors occurred:
[ERROR Port-10250]: Port 10250 is in use
[preflight] If you know what you are doing, you can make a check non-fatal with –ignore-preflight-errors=…
What should you do?
Solution
Remove the kubelet that snap installed;
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Problem scenario
Using a Debian/Ubuntu distribution of Linux, how do you install kubeadm, kubectl, and/or kubelet?
You want to install kubeadm, kubectl or kubelet (without retrieving the binary of the file from a website and do a regular installation). What do you do?
Solution
Here is another way to install kubectl, kubelet and kubeadm:
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add
sudo apt-add-repository “deb http://apt.kubernetes.io/ kubernetes-xenial main”
sudo apt-get -y install kubeadm kubelet kubectl
(If you can download a file from the internet and want to avoid using apt commands,
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Problem scenario
What is a good command to see the overall health of your Kubernetes servers (nodes)?
Solution
Run this command: kubectl describe nodes
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Continue reading “How Do You Briefly Look at the Conditions of Kubernetes Nodes?”