Kuberntes is becoming more and more popular in application deployment and management as a container-orchestration system. Below are some of the useful shell scripts or commands that can be used in Kubernetes world based on my daily experience.
Providing pod spec from command line
command
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
name: <POD_NAME>
spec:
containers:
- name: <CONTAINER_NAME>
image: <DOCKER_IMAGE>
args:
- sleep
- "1000000"
EOF
Running a command in a specified pod
command
kubectl exec network-policy-client-pod -- curl <secure pod cluster ip address>
Retrieving a specific value from a yaml file defined in a configmap
command
kubectl get configmaps job-configs -o jsonpath="{.data.job-config\.yaml}" | yq read - kube.image.job
Waiting for k8s job been created
Scripts
timeout=$(( $(date +%s) + 60 ))
while ! kubectl get job whatever 2>/dev/null; do
[ $(date +%s) -gt $timeout ] && exit 1
sleep 5
done
This command is quite useful as kubectl wait will exit immediatelly if the resource is not yet created.