FAQ / Nice to know¶
Issues with BTRFS¶
- As @jaredallard pointed out, people running
k3don a system with btrfs, may need to mount
/dev/mapperinto the nodes for the setup to work.
- This will do:
k3d cluster create CLUSTER_NAME -v /dev/mapper:/dev/mapper
Issues with ZFS¶
- k3s currently has no support for ZFS and thus, creating multi-server setups (e.g.
k3d cluster create multiserver --servers 3) fails, because the initializing server node (server flag
--cluster-init) errors out with the following log:
starting kubernetes: preparing server: start cluster and https: raft_init(): io: create I/O capabilities probe file: posix_allocate: operation not supported on socket
- This issue can be worked around by providing docker with a different filesystem (that’s also better for docker-in-docker stuff).
- A possible solution can be found here: https://github.com/rancher/k3s/issues/1688#issuecomment-619570374
Pods evicted due to lack of disk space¶
- Pods go to evicted state after doing X
- Related issues: #133 - Pods evicted due to
NodeHasDiskPressure(collection of #119 and #130)
- Background: somehow docker runs out of space for the k3d node containers, which triggers a hard eviction in the kubelet
- Possible fix/workaround by @zer0def:
- use a docker storage driver which cleans up properly (e.g. overlay2)
- clean up or expand docker root filesystem
- change the kubelet’s eviction thresholds upon cluster creation:
k3d cluster create --k3s-agent-arg '--kubelet-arg=eviction-hard=imagefs.available<1%,nodefs.available<1%' --k3s-agent-arg '--kubelet-arg=eviction-minimum-reclaim=imagefs.available=1%,nodefs.available=1%'
Restarting a multi-server cluster or the initializing server node fails¶
- What you do: You create a cluster with more than one server node and later, you either stop
server-0or stop/start the whole cluster
- What fails: After the restart, you cannot connect to the cluster anymore and
kubectlwill give you a lot of errors
- What causes this issue: it’s a known issue with dqlite in
k3swhich doesn’t allow the initializing server node to go down
- What’s the solution: Hopefully, this will be solved by the planned replacement of dqlite with embedded etcd in k3s
- Related issues: #262
Passing additional arguments/flags to k3s (and on to e.g. the kube-apiserver)¶
- The Problem: Passing a feature flag to the Kubernetes API Server running inside k3s.
- Example: you want to enable the EphemeralContainers feature flag in Kubernetes
k3d cluster create --k3s-server-arg '--kube-apiserver-arg=feature-gates=EphemeralContainers=true'
Note: Be aware of where the flags require dashes (
--) and where not.
- the k3s flag (
--kube-apiserver-arg) has the dashes
- the kube-apiserver flag
feature-gatesdoesn’t have them (k3s adds them internally)
- the k3s flag (
k3d cluster create k3d-one --k3s-server-arg --cluster-cidr="10.118.0.0/17" --k3s-server-arg --service-cidr="10.118.128.0/17" --k3s-server-arg --disable=servicelb --k3s-server-arg --disable=traefik --verbose
- Note: There are many ways to use the
'quotes, just be aware, that sometimes shells also try to interpret/interpolate parts of the commands
How to access services (like a database) running on my Docker Host Machine¶
- As of version v3.1.0, we’re injecting the
host.k3d.internalentry into the k3d containers (k3s nodes) and into the CoreDNS ConfigMap, enabling you to access your host system by referring to it as