kubernetes - Nodes

By: జగదేశ్ on 6:20 PM

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A node is basically a worker machine where kubernetes creates pods. The node can be a VM or

physical machine. Every node in the cluster will have some services running which include

docker, kubelet and kube-proxy

The node is not generally created through kubernetes but by cloud providers or Vm based

softwares. Once created and attached to kubernetes cluster , a node object is created which will

be used to check if the node is valid or not. If the node is valid and all necessary worker node

services are running, then the node is eligible for pod creation. If the node is not valid ,it will

wait until the node become valid to create pod.

Who will handle the nodes?

Node controller is the master node component which take care of the nodes. It has some of the

responsibilities including node health check also making sure all nodes in the node controller list are up to date.

To get the nodes available in the cluster, use

[root@manja17-I13330 ~]# kubectl get nodes

NAME                 STATUS ROLES AGE       VERSION

manja17-i13330  Ready master    8d v1.10.2

work-node1        Ready <none>   8d v1.10.2

work-node2        Ready <none>   8d v1.10.2

To get more details about the node use,

To get more insight into the node , we can use the describe command as,
[root@manja17-I13330 ~]# kubectl describe node work-node1

Name:               work-node1

Roles:              <none>

Labels:             app=backend

                   beta.kubernetes.io/arch=amd64

                   beta.kubernetes.io/os=linux

                   kubernetes.io/hostname=work-node1

                   label=node1

Annotations:        node.alpha.kubernetes.io/ttl=0

                   volumes.kubernetes.io/controller-managed-attach-detach=true

CreationTimestamp: Tue, 01 May 2018 09:19:56 -0400
Taints: <none>
Unschedulable: false
Conditions:
Type Status LastHeartbeatTime LastTransitionTime Reason Message
---- ------ ----------------- ------------------ ------ -------
OutOfDisk False Thu, 10 May 2018 00:40:10 -0400 Tue, 01 May 2018 09:19:55 -0400 KubeletHasSufficientDisk kubelet has sufficient disk space available

MemoryPressure False Thu, 10 May 2018 00:40:10 -0400 Tue, 01 May 2018 09:19:55 -0400 KubeletHasSufficientMemory kubelet has sufficient memory available

DiskPressure False Thu, 10 May 2018 00:40:10 -0400 Tue, 01 May 2018 09:19:55 -0400 KubeletHasNoDiskPressure kubelet has no disk pressure

PIDPressure False Thu, 10 May 2018 00:40:10 -0400 Tue, 01 May 2018 09:19:55 -0400 KubeletHasSufficientPID kubelet has sufficient PID available

Ready True Thu, 10 May 2018 00:40:10 -0400 Tue, 01 May 2018 09:20:45 -0400 KubeletReady kubelet is posting ready status

Addresses:

 InternalIP:  10.0.2.15

 Hostname:    work-node1

Capacity:

cpu:                1

ephemeral-storage:  39269648Ki

hugepages-2Mi:      0

memory:             1883484Ki

pods:               110

Allocatable:

cpu:                1

ephemeral-storage:  36190907537

hugepages-2Mi:      0

memory:             1781084Ki

pods:               110

System Info:

Machine ID:                 d43fcbfca85f47288d8b553380d86c8e

System UUID:                D43FCBFC-A85F-4728-8D8B-553380D86C8E

Boot ID:                    324be3e3-a221-46d9-b724-50f2daa061c2

Kernel Version:             3.10.0-693.21.1.el7.x86_64

OS Image:                   CentOS Linux 7 (Core)

Operating System:           linux

Architecture:               amd64

Container Runtime Version:  docker://1.13.1

Kubelet Version:            v1.10.2

Kube-Proxy Version:         v1.10.2

ExternalID:                  work-node1

Non-terminated Pods:         (3 in total)

 Namespace                  Name CPU Requests  CPU Limits Memory Requests Memory Limits

 ---------                  ---- ------------  ---------- --------------- -------------

 default                    myapp-pod 0 (0%)       0 (0%) 0 (0%) 0 (0%)

 kube-system                kube-proxy-9qpxq 0 (0%)       0 (0%) 0 (0%) 0 (0%)

 kube-system                weave-net-frhh9 20m (2%)      0 (0%) 0 (0%) 0 (0%)

Allocated resources:

 (Total limits may be over 100 percent, i.e., overcommitted.)

 CPU Requests  CPU Limits Memory Requests  Memory Limits

 ------------  ---------- ---------------  -------------

 20m (2%)      0 (0%) 0 (0%)           0 (0%)

Events:         <none>