zulhfreelancer

How to install promtool by Prometheus?

# Fetch latest version
TAG=$(curl -s https://api.github.com/repos/prometheus/prometheus/releases | jq -r '.[] | .tag_name' | head -n 1)
echo $TAG

# Remove the `v` prefix
VERSION=$(echo $TAG | sed 's/v//')
echo $VERSION

zulhfreelancer

How to query Prometheus from local CLI / Terminal

Requirements

promtool - see installation steps here

Command

promtool query instant '' '' | jq

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How to filter Kubernetes nodes by label using kubectl and jq

# Get all control-plane nodes
kubectl get nodes -o json | jq -r '.items[] | select(.metadata.labels."node-role.kubernetes.io/control-plane"=="true").metadata.name'

# Get all worker nodes
kubectl get nodes -o json | jq -r '.items[] | select(.metadata.labels."node-role.kubernetes.io/control-plane"!="true").metadata.name'

zulhfreelancer

Get all pods with restart count more than zero / 0, with headers, node name and restart count

k get pods -A -o json | jq -r '["NAMESPACE", "POD_NAME", "NODE_NAME", "RESTART_COUNT"], (.items[] | select(.status.containerStatuses[].restartCount > 0) | [.metadata.namespace, .metadata.name, .spec.nodeName, .status.containerStatuses[].restartCount]) | @tsv' | sort -k1,1 | column -t -s $'\t'

Get all pods with restart count more than zero / 0, without headers, just namespace and pod name

k get pods -A -o json | jq -r '(.items[] | select(.status.containerStatuses[].restartCount > 0) | [.metadata.namespace, .metadata.name]) | @tsv' | sort -k1,1 | column -t -s $'\t'

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# List all deleted pods
kubectl get pods -o json | jq -r '.items[] | select(.metadata.deletionTimestamp != null)'

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# Search by key
kubectl get nodes -o json | jq -r '.items[] | select(.spec.taints[]? | select(.key == "foo/bar")) | .metadata.name'

# Search by key and value
kubectl get nodes -o json | jq -r '.items[] | select(.spec.taints[]? | select(.key=="foo/bar" and .value=="baz")) | .metadata.name'

zulhfreelancer

kubectl get nodes -o json | jq -r '.items | map({name: (.metadata.name + ""), type: (if (.metadata.labels | has("node-role.kubernetes.io/control-plane")) then "control-plane" else "worker" end), status: (.status.conditions[] | select(.type=="Ready") | if .status == "True" then "Ready" else "NotReady" end)}) | group_by(.type)  | (["NODE_NAME", "NODE_TYPE", "NODE_STATUS"] | (., map(length*"-"))), (.[][] | [.name,.type,.status]) | @tsv' | column -ts $'\t'

zulhfreelancer

apiVersion: apps/v1
kind: Deployment
metadata:
  name: netshoot
  labels:
    app: netshoot
spec:
  replicas: 1
  selector:
    matchLabels:

zulhfreelancer

How to convert YAML to JSON using yq?

FYI, I'm using yq version 4 by mikefarah

Command:

cat <YAML-FILE-NAME> | yq e -j

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Problem

How to fix Nginx ingress controller "certificate signed by unknown authority" error?

Error:

"Internal error occurred: failed calling webhook \"validate.nginx.ingress.kubernetes.io\": failed to call webhook: Post \"https://nginx-ingress-ingress-nginx-controller-admission.default.svc:443/networking/v1/ingresses?timeout=10s\": x509: certificate signed by unknown authority"