I am on the lab -- troubleshoot controlplane failures, and I do not find the kub . . .

Kubernetes
#1

Mayur Sharma:
I am on the lab – troubleshoot controlplane failures, and I do not find the kubelet service in the master node, can anyone tell me why it is not there or I am expecting it wrongly.

I expect the kubelet to be present on master node as controlplane components are deployed via kubeadm and components are deployed as static pod, so I think kubelet has installed all controlplane components as static pod

controlplane $ cd /etc/systemd/system/   
controlplane $ ls
dbus-org.freedesktop.resolve1.service   default.target.wants  multi-user.target.wants  sysinit.target.wants
dbus-org.freedesktop.timesync1.service  getty.target.wants    sockets.target.wants     timers.target.wants
controlplane $
#2

Karim Meslem:
Remember the analogy? The kubelet is the captain of the ship. The ship = worker node.

#3

Mayur Sharma:
@Karim Meslem, Yes, I remember it, but wondering then how static pods are installed on master node then, who install it and where is the configuration to set the static pod directory as /etc/kubernetes/manifest

#4

Karim Meslem:
defined by staticPodPath in the kubelet config file. first find the kubelet config file:
ps -ef | grep kubelet | grep config
outputs something like this:

#5

Karim Meslem:
root 5143 1 0 11:19 ? 00:00:38 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=*/var/lib/kubelet/config.yaml* --network-plugin=cni --pod-infra-container-image=<http://k8s.gcr.io/pause:3.2|k8s.gcr.io/pause:3.2>

#6

Mayur Sharma:
@Karim Meslem: Not following you, I am talking about master node, and there is no kubelet there. so cannot find the kubelet config file.
The commands you shared would work on worker node.
let me know if I am missing anything in your statements

#7

Karim Meslem:
then open the file, e.g. /var/lib/kubelet/config.yaml and search for “staticPodPath”. This will point you to the manifests directory as configured on the system.

#8

Karim Meslem:
this is on master node

#9

Mayur Sharma:
how do you find the kubelet on master node

#10

Mayur Sharma:

controlplane $ ps -ef | grep kubelet              
root       620    12  0 11:40 pts/1    00:00:00 grep --color=auto kubelet
controlplane $

I got nothing

#11

Karim Meslem:
ps -ef | grep kubelet?

#12

Karim Meslem:
its not there in your controlplane node, but I might expect on the worker node to be there.

#13

Karim Meslem:
I am not at that lab yet, so I was referring to your question of “where is the staic pod (manifests directory)” defined

#14

Mayur Sharma:
On worker node kubelet is there, but I want to know for master node.

Rephrasing it here:

  1. how static pods are installed on master node then, I think kubeadm deos that but how, using which component, and
  2. where is the configuration to set the static pod directory as /etc/kubernetes/manifest
#15

Mayur Sharma:
@Karim Meslem hope it clear now.

#16

Karim Meslem:
perhaps part of the answer of that lab is that you have to create the kubelet yourself on the controlplane node. I don’t know

#17

Mayur Sharma:
@Karim Meslem: no, the question was totally different and I could solve that.

Doubt got raised after I notice that all components on controlplane are installed are static pods.

So, someone has to installed it, who is it? I beleive kubeadm.
Then, how the static pod directory is configured and who looks it for auto scheduling if kubelet is not there.

#18

Karim Meslem:
now I’m confused :wink: scheduling (decision) is done by the scheduler, not the kubelet.

#19

Mayur Sharma:
static pods and daemon sets are not scheduled by scheduler :slightly_smiling_face:

#20

Karim Meslem:
yeah, let me stick to what I know: kubelet and kube-proxy are worker node components and I wouldn’t expect them to be present on a contolplane node.