FAQ¶
Issues with BTRFS¶
- As @jaredallard pointed out, people running
k3d
on a system with btrfs, may need to mount/dev/mapper
into the nodes for the setup to work.- This will do:
k3d cluster create CLUSTER_NAME -v /dev/mapper:/dev/mapper
- This will do:
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-arg '--kubelet-arg=eviction-hard=imagefs.available<1%,nodefs.available<1%@agent:*' \ --k3s-arg '--kubelet-arg=eviction-minimum-reclaim=imagefs.available=1%,nodefs.available=1%@agent:*'
- Related issues: #133 - Pods evicted due to
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-0
or stop/start the whole cluster - What fails: After the restart, you cannot connect to the cluster anymore and
kubectl
will give you a lot of errors - What causes this issue: it’s a known issue with dqlite in
k3s
which 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
- Solution:
k3d cluster create --k3s-arg '--kube-apiserver-arg=feature-gates=EphemeralContainers=true@server:*'
- 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-gates
doesn’t have them (k3s adds them internally)
- the k3s flag (
- Note: Be aware of where the flags require dashes (
-
Second example:
k3d cluster create k3d-one \ --k3s-arg "--cluster-cidr=10.118.0.0/17@server:*" \ --k3s-arg "--service-cidr=10.118.128.0/17@server:*" \ --k3s-arg "--disable=servicelb@server:*" \ --k3s-arg "--disable=traefik@server:*" \ --verbose
- Note: There are many ways to use the
"
and'
quotes, just be aware, that sometimes shells also try to interpret/interpolate parts of the commands
- Note: There are many ways to use the
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.internal
entry into the k3d containers (k3s nodes) and into the CoreDNS ConfigMap, enabling you to access your host system by referring to it ashost.k3d.internal
Running behind a corporate proxy¶
Running k3d behind a corporate proxy can lead to some issues with k3d that have already been reported in more than one issue.
Some can be fixed by passing the HTTP_PROXY
environment variables to k3d, some have to be fixed in docker’s daemon.json
file and some are as easy as adding a volume mount.
Pods fail to start: x509: certificate signed by unknown authority
¶
-
Example Error Message:
Failed to create pod sandbox: rpc error: code = Unknown desc = failed to get sandbox image "docker.io/rancher/pause:3.1": failed to pull image "docker.io/rancher/pause:3.1": failed to pull and unpack image "docker.io/rancher/pause:3.1": failed to resolve reference "docker.io/rancher/pause:3.1": failed to do request: Head https://registry-1.docker.io/v2/rancher/pause/manifests/3.1: x509: certificate signed by unknown authority
- Problem: inside the container, the certificate of the corporate proxy cannot be validated
- Possible Solution: Mounting the CA Certificate from your host into the node containers at start time via
k3d cluster create --volume /path/to/your/certs.crt:/etc/ssl/certs/yourcert.crt
- Issue: rancher/k3d#535
Spurious PID entries in /proc
after deleting k3d
cluster with shared mounts¶
- When you perform cluster create and deletion operations multiple times with same cluster name and shared volume mounts, it was observed that
grep k3d /proc/*/mountinfo
shows many spurious entries - Problem: Due to above, at times you’ll see
no space left on device: unknown
when a pod is scheduled to the nodes - If you observe anything of above sort you can check for inaccessible file systems and unmount them by using below command (note: please remove
xargs umount -l
and check for the diff o/p first) diff <(df -ha | grep pods | awk '{print $NF}') <(df -h | grep pods | awk '{print $NF}') | awk '{print $2}' | xargs umount -l
- As per the conversation on rancher/k3d#594 above issue wasn’t reported/known earlier and so there are high chances that it’s not universal.
[SOLVED] Nodes fail to start or get stuck in NotReady
state with log nf_conntrack_max: permission denied
¶
Problem¶
- When: This happens when running k3d on a Linux system with a kernel version >= 5.12.2 (and others like >= 5.11.19) when creating a new cluster
- the node(s) stop or get stuck with a log line like this:
<TIMESTAMP> F0516 05:05:31.782902 7 server.go:495] open /proc/sys/net/netfilter/nf_conntrack_max: permission denied
- the node(s) stop or get stuck with a log line like this:
- Why: The issue was introduced by a change in the Linux kernel (Changelog 5.12.2: Commit), that changed the netfilter_conntrack behavior in a way that
kube-proxy
is not able to set thenf_conntrack_max
value anymore
Workaround¶
-
Workaround: as a workaround, we can tell
kube-proxy
to not even try to set this value:k3d cluster create \ --k3s-arg "--kube-proxy-arg=conntrack-max-per-core=0@server:*" \ --k3s-arg "--kube-proxy-arg=conntrack-max-per-core=0@agent:*" \ --image rancher/k3s:v1.20.6-k3s
Fix¶
- Note: k3d v4.4.5 already uses rancher/k3s:v1.21.1-k3s1 as the new default k3s image, so no workarounds needed there!
This is going to be fixed “upstream” in k3s itself in rancher/k3s#3337 and backported to k3s versions as low as v1.18.
- The fix was released and backported in k3s, so you don’t need to use the workaround when using one of the following k3s versions (or later ones)
- v1.18.19-k3s1 (rancher/k3s#3344)
- v1.19.11-k3s1 (rancher/k3s#3343)
- v1.20.7-k3s1 (rancher/k3s#3342)
- v1.21.1-k3s1 (rancher/k3s#3341))
- Issue Reference: rancher/k3s#607
DockerHub Pull Rate Limit¶
Problem¶
You’re deploying something to the cluster using an image from DockerHub and the image fails to be pulled, with a 429
response code and a message saying You have reached your pull rate limit. You may increase the limit by authenticating and upgrading
.
Cause¶
This is caused by DockerHub’s pull rate limit (see https://docs.docker.com/docker-hub/download-rate-limit/), which limits pulls from unauthenticated/anonymous users to 100 pulls per hour and for authenticated users (not paying customers) to 200 pulls per hour (as of the time of writing).
Solution¶
a) use images from a private registry, e.g. configured as a pull-through cache for DockerHub
b) use a different public registry without such limitations, if the same image is stored there
c) authenticate containerd inside k3s/k3d to use your DockerHub user
(c) Authenticate Containerd against DockerHub¶
-
Create a registry configuration file for containerd:
# saved as e.g. $HOME/registries.yaml configs: "docker.io": auth: username: "$USERNAME" password: "$PASSWORD"
-
Create a k3d cluster using that config:
k3d cluster create --registry-config $HOME/registries.yaml
-
Profit. That’s it. In the test for this, we pulled the same image 120 times in a row (confirmed, that pull numbers went up), without being rate limited (as a non-paying, normal user)