docs: Documenting Kubelet path

Fixes: k0sproject#2599
Signed-off-by: Manuel Hutter <[email protected]>

docs/storage.md

@@ -106,6 +106,10 @@ When the storage solution implements Container Storage Interface (CSI), containe
 
 ![k0s storage](img/k0s_storage.png)
 
+### Installing 3rd party storage solutions
+
+Follow your storage driver's installation instructions. Note that the kubelet installed by k0s uses a slightly differen path for its working directory (`/varlib/k0s/kubelet` instead of `/var/lib/kubelet`). Consult the CSI driver's configuration documentation on how to customize this path.
+
 ## Example storage solutions
 
 Different Kubernetes storage solutions are explained in the [official Kubernetes storage documentation](https://kubernetes.io/docs/concepts/storage/volumes/). All of them can be used with k0s. Here are some popular ones:
@@ -119,4 +123,4 @@ Different Kubernetes storage solutions are explained in the [official Kubernetes
 - Azure Disk
 - Portworx
 
-If you are looking for a fault-tolerant storage with data replication, you can find a k0s tutorial for configuring Ceph storage with Rook [in here](examples/rook-ceph.md).
+If you are looking for a fault-tolerant storage with data replication, you can find a k0s tutorial for configuring Ceph storage with Rook [in here](examples/rook-ceph.md).

docs/troubleshooting.md

@@ -148,4 +148,10 @@ Due to removal of the embedded docker-shim from Kubelet, the Kubelets embedded [
 
 Unfortunately this does not work on when using Docker via cri-dockerd shim. There's currently no easy workarounds for this.
 
-In the future kubelet will be refactored to get the container metrics from CRI interface rather than from the runtime directly. This work is specified and followed up in [KEP-2371](https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/2371-cri-pod-container-stats/README.md) but until that work completes the only option is to run a standalone cAdvisor. There's ongoing [effort](https://github.com/kubernetes/website/issues/30681) to both document the current shortcomings and how to run standalone cAdvisor in Kubernetes community.
+In the future kubelet will be refactored to get the container metrics from CRI interface rather than from the runtime directly. This work is specified and followed up in [KEP-2371](https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/2371-cri-pod-container-stats/README.md) but until that work completes the only option is to run a standalone cAdvisor. There's ongoing [effort](https://github.com/kubernetes/website/issues/30681) to both document the current shortcomings and how to run standalone cAdvisor in Kubernetes community.
+
+## Customized configurations
+
+* All data directories reside under `/var/lib/k0s`, for example:
+  * `/var/lib/k0s/kubelet`
+  * `/var/lib/k0s/etcd`