I'm writing some scripts that check the system to make sure of some cluster characteristics. Things running on private IP address spaces, etc. These checks are just a manual step when setting up a cluster, and used just for sanity checking.
They'll be run on each node, but I'd like a set of them to run when on the master node. Is there a bash, curl, kubectl, or another command that has information indicating the current node is a master node?
The master(s) usually has the 'master' role associated with it. For example:
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
ip-x-x-x-x.us-west-2.compute.internal Ready <none> 7d v1.11.2
ip-x-x-x-x.us-west-2.compute.internal Ready master 78d v1.11.2
ip-x-x-x-x.us-west-2.compute.internal Ready <none> 7d v1.11.2
ip-x-x-x-x.us-west-2.compute.internal Ready <none> 7d v1.11.2
ip-x-x-x-x.us-west-2.compute.internal Ready <none> 7d v1.11.2It also has a label node-role.kubernetes.io/master associated with it. For example:
$ kubectl get node ip-x-x-x-x.us-west-2.compute.internal -o=yaml
apiVersion: v1
kind: Node
metadata:
annotations:
kubeadm.alpha.kubernetes.io/cri-socket: /var/run/dockershim.sock
node.alpha.kubernetes.io/ttl: "0"
projectcalico.org/IPv4Address: x.x.x.x/20
volumes.kubernetes.io/controller-managed-attach-detach: "true"
creationTimestamp: 2018-07-23T21:10:22Z
labels:
beta.kubernetes.io/arch: amd64
beta.kubernetes.io/instance-type: t3.medium
beta.kubernetes.io/os: linux
failure-domain.beta.kubernetes.io/region: us-west-2
failure-domain.beta.kubernetes.io/zone: us-west-2c
kubernetes.io/hostname: ip-x-x-x-x.us-west-2.compute.internal
node-role.kubernetes.io/master: ""Some more ways:
$ kubectl cluster-info
Kubernetes master is running at https://node1.example.com:8443
...You can use kubectl with label selector:
$ kubectl get nodes -l node-role.kubernetes.io/master=true
NAME STATUS ROLES AGE VERSION
node1.example.com Ready master 1d v1.10.5
node2.example.com Ready master 1d v1.10.5And you can get specific data via jsonpath, e.g master IPs/hostnames:
$ kubectl get nodes -l node-role.kubernetes.io/master=true -o 'jsonpath={.items[*].status.addresses[?(@.type=="InternalIP")].address}'
192.168.168.197 192.168.168.198
$ kubectl get nodes -l node-role.kubernetes.io/master=true -o 'jsonpath={.items[*].status.addresses[?(@.type=="Hostname")].address}'
node1.example.com node2.example.com