Troubleshooting#
There are few common cases we've seen where k0s fails to run properly.
CoreDNS in crashloop#
The most common case we've encountered so far has been CoreDNS getting into crashloop on the node(s).
With kubectl you see something like this:
$ kubectl get pod --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system calico-kube-controllers-5f6546844f-25px6 1/1 Running 0 167m
kube-system calico-node-fwjx5 1/1 Running 0 164m
kube-system calico-node-t4tx5 1/1 Running 0 164m
kube-system calico-node-whwsg 1/1 Running 0 164m
kube-system coredns-5c98d7d4d8-tfs4q 1/1 Error 17 167m
kube-system konnectivity-agent-9jkfd 1/1 Running 0 164m
kube-system konnectivity-agent-bvhdb 1/1 Running 0 164m
kube-system konnectivity-agent-r6mzj 1/1 Running 0 164m
kube-system kube-proxy-kr2r9 1/1 Running 0 164m
kube-system kube-proxy-tbljr 1/1 Running 0 164m
kube-system kube-proxy-xbw7p 1/1 Running 0 164m
kube-system metrics-server-7d4bcb75dd-pqkrs 1/1 Running 0 167m
When you check the logs, it'll show something like this:
$ kubectl -n kube-system logs coredns-5c98d7d4d8-tfs4q
plugin/loop: Loop (127.0.0.1:55953 -> :1053) detected for zone ".", see https://coredns.io/plugins/loop#troubleshooting. Query: "HINFO 4547991504243258144.3688648895315093531."
This is most often caused by systemd-resolved stub (or something similar) running locally and CoreDNS detects a possible loop with DNS queries.
The easiest but most crude way to workaround is to disable the systemd-resolved stub and revert the hosts /etc/resolv.conf
to original
Read more at CoreDNS troubleshooting docs.
k0s server
fails on ARM boxes#
In the logs you probably see ETCD not starting up properly.
Etcd is not fully supported on ARM architecture, thus you need to run k0s server
and thus also etcd process with env ETCD_UNSUPPORTED_ARCH=arm64
.
As Etcd is not fully supported on ARM architecture it also means that k0s controlplane with etcd itself is not fully supported on ARM either.
Pods pending when using cloud providers#
Once we enable cloud provider support on kubelet on worker nodes, kubelet will automatically add a taint node.cloudprovider.kubernetes.io/uninitialized
for the node. This tain will prevent normal workloads to be scheduled on the node until the cloud provider controller actually runs second initialization on the node and removes the taint. This means that these nodes are not available for scheduling until the cloud provider controller is actually successfully running on the cluster.
For troubleshooting your specific cloud provider see its documentation.
k0s not working with read only /usr
#
By default k0s does not run on nodes where /usr
is read only.
This can be fixed by changing the default path for volumePluginDir
in your k0s config. You will need to change to values, one for the kubelet itself, and one for Calico.
Here is a snippet of an example config with the default values changed:
spec:
controllerManager:
extraArgs:
flex-volume-plugin-dir: "/etc/kubernetes/kubelet-plugins/volume/exec"
network:
calico:
flexVolumeDriverPath: /etc/k0s/kubelet-plugins/volume/exec/nodeagent~uds
workerProfiles:
- name: coreos
values:
volumePluginDir: /etc/k0s/kubelet-plugins/volume/exec/
With this config you can start your server as usual. Any workers will need to be started with
k0s worker --profile coreos [TOKEN]
Profiling#
We drop any debug related information and symbols from the compiled binary by utilzing -w -s
linker flags.
To keep those symbols use DEBUG
env variable:
$ DEBUG=true make k0s
CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags=" -X github.com/k0sproject/k0s/pkg/build.Version=v0.9.0-7-g97e5bac -X \"github.com/k0sproject/k0s/pkg/build.EulaNotice=\" -X github.com/k0sproject/k0s/pkg/telemetry.segmentToken=" \
-o k0s.code main.go
Any value not equal to the "false" would work.
To add custom linker flags use LDFLAGS
variable.
$ LD_FLAGS="--custom-flag=value" make k0s
CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="--custom-flag=value -X github.com/k0sproject/k0s/pkg/build.Version=v0.9.0-7-g97e5bac -X \"github.com/k0sproject/k0s/pkg/build.EulaNotice=\" -X github.com/k0sproject/k0s/pkg/telemetry.segmentToken=" \
-o k0s.code main.go