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A set of oneliners that has been the most useful for me.

JQ

jq is like sed for JSON data.

Listing an array of AWS instances from providerID + node name + labels

for i in {i-001,i-002}; do jq -r --arg i "$i" '.items[] | select(.spec.providerID | contains($i)) | {node: $i, hostname: .metadata.labels."kubernetes.io/hostname", roles: .metadata.labels | with_entries(select(.key | test("^node-role.kubernetes.io")))}' my-nodes.json ; done

for i in {i-001,i-002}; do
jq -r --arg i "$i" '
    .items[] |
    select(.spec.providerID | contains($i)) |
    {
        node: $i,
        hostname: .metadata.labels."kubernetes.io/hostname",
        roles: .metadata.labels | with_entries(select(.key | test("^node-role.kubernetes.io")))
    }
' my-nodes.json
done

Output: 

{
  "node": "i-001",
  "hostname": "ip-10-001-002-34.eu-west-1.compute.internal",
  "roles": {
    "node-role.kubernetes.io": "infra",
    "node-role.kubernetes.io/infra": "",
    "node-role.kubernetes.io/worker": ""
  }

  • Breakdown explanation

    • test: This is a jq function that tests if a string matches a regular expression pattern.
    • "^node-role.kubernetes.io": This is the regular expression pattern that specifies the string to match. In this case, ^ matches the start of the string, and node-role.kubernetes.io is the pattern we want to match.

When applied to each key in the labels object, test("^node-role.kubernetes.io") returns true if the key matches the pattern "^node-role.kubernetes.io" (i.e., if the key starts with "node-role.kubernetes.io"), and false otherwise.

This filter function is used to select only the keys in the labels object that start with node-role.kubernetes.io, effectively filtering out other keys. This allows us to extract only the labels related to node roles from the labels object.

Get specific fields values from multiple containers inside a pod

oc get pods -o json | jq ".items[] | { pod_name: .metadata.name, containers: ( .spec.containers[].resources | { requests } ) }"

oc get pods -o json | jq '
.items[] |
{
    pod_name: .metadata.name,
    containers: (
        .spec.containers[].resources |
        {
            requests
            }
        )
    }
'

Output: 

{
  "pod_name": "logging-loki-gateway-68d8b7744b-qvlw6",
  "containers": {
    "requests": {
      "cpu": "500m",
      "memory": "500Mi"
    }
  }
}
{
  "pod_name": "logging-loki-gateway-68d8b7744b-qvlw6",
  "containers": {
    "requests": null

Extract all unique "usernames" from a json file

cat data.json | jq .user.username -r | sort | uniq -c | sort -n

Get specific fields values from multiple pods

Get the pod name, the creationTimestamp and the node where the pod is hosted.

  oc get pods -o json | jq -r '.items[] | .metadata.name + " ===> " +.metadata.creationTimestamp + " ===> " +.spec.nodeName'

Output: 

my-nginx-1 ===> 2024-04-22T10:10:00Z ===> worker-hevs-westeurope1-xxxx
my-nginx-2 ===> 2024-04-23T10:10:00Z ===> worker-hevs-westeurope1-xxxx