How do you increase maximum pods per node in K3S? - kubernetes

Question

I have tried setting max nodes per pod using the following upon install:
curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="--max-pods 250" sh -s -
However, the K3s server will then fail to load. It appears that the --max-pods flag has been deprecated per the kubernetes docs:
--max-pods int32 Default: 110
(DEPRECATED: This parameter should be set via the config file
specified by the Kubelet's --config flag. See
https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/
for more information.)
So with K3s, where is that kubelet config file and can/should it be set using something like the above method?

Answer 1

To update your existing installation with an increased max-pods, add a kubelet config file into a k3s associated location such as /etc/rancher/k3s/kubelet.config:
apiVersion: kubelet.config.k8s.io/v1beta1
kind: KubeletConfiguration
maxPods: 250
edit /etc/systemd/system/k3s.service to change the k3s server args:
ExecStart=/usr/local/bin/k3s \
server \
'--disable' \
'servicelb' \
'--disable' \
'traefik' \
'--kubelet-arg=config=/etc/rancher/k3s/kubelet.config'
reload systemctl to pick up the service change:
sudo systemctl daemon-reload
restart k3s:
sudo systemctl restart k3s
Check the output of describe nodes with kubectl describe <node> and look for allocatable resources:
Allocatable:
cpu: 32
ephemeral-storage: 199789251223
hugepages-1Gi: 0
hugepages-2Mi: 0
memory: 131811756Ki
pods: 250
and a message noting that allocatable node limit has been updated in Events:
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Starting 20m kube-proxy Starting kube-proxy.
Normal Starting 20m kubelet Starting kubelet.
...
Normal NodeNotReady 7m52s kubelet Node <node> status is now: NodeNotReady
Normal NodeAllocatableEnforced 7m50s kubelet Updated Node Allocatable limit across pods
Normal NodeReady 7m50s kubelet Node <node> status is now: NodeReady

Answer 2

As described in documentation, it is possible to set the Kubelet's configuration parameters via
an on-disk config file.
NOTE: Using an on-disk config file, we can set only subset of the Kubelet's configuration parameters, that we want to override, all other Kubelet configuration values are left at their built-in defaults, unless overridden by flags.
I've created simple config file to override maxPods value (default 110):
apiVersion: kubelet.config.k8s.io/v1beta1
kind: KubeletConfiguration
maxPods: 250
And then we have to pass this config file as an argument during K3s installation (I recommend to specify absolute pathname):
curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="--kubelet-arg=config=<KUBELET_CONFIG_FILE_LOCATION>" sh -
Finally we can check that maxPods is equal to 250:
# kubectl describe nodes <NODE_NAME> | grep -i pod
pods: 250
pods: 250
PodCIDR: 10.42.0.0/24
PodCIDRs: 10.42.0.0/24
In addition you can find interesting discussion here, I believe you can find there another way to solve your issue.