I have installed a Kubernetes cluster using kind k8s as it was easier to setup and run in my local VM. I also installed Docker separately. I then created a docker image for Spring boot application I built for printing messages to the stdout. It was then added to kind k8s local registry. Using this newly created local image, I created a deployment in the kubernetes cluster using kubectl apply -f config.yaml CLI command. Using similar method I've also deployed fluentd hoping to collect logs from /var/log/containers that would be mounted to fluentD container.
I noticed /var/log/containers/ symlink link doesn't exist. However there is /var/lib/docker/containers/ and it has folders for some containers that were created in the past. None of the new container IDs doesn't seem to exist in /var/lib/docker/containers/ either.
I can see logs in the console when I run kubectl logs pod-name even though I'm unable to find the logs in the local storage.
Following the answer in another thread given by stackoverflow member, I was able to get some information but not all.
I have confirmed Docker is configured with json logging driver by running the following command.
docker info | grep -i logging
When I run the following command (found in the thread given above) I can get the image ID.
kubectl get pod pod-name -ojsonpath='{.status.containerStatuses[0].containerID}'
However I cannot use it to inspect the docker image using docker inspect as Docker is not aware of such image which I assume it due to the fact it is managed by kind control plane.
Appreciate if the experts in the forum can assist to identify where the logs are written and recreate the /var/log/containers symbolink link to access the container logs.
It's absolutely normal that your local installed Docker doesn't have containers running in pod created by kind Kubernetes. Let me explain why.
First, we need to figure out, why kind Kubernetes actually needs Docker. It needs it not for running containers inside pods. It needs Docker to create container which will be Kubernetes node - and on this container you will have pods which will have containers that are you looking for.
kind is a tool for running local Kubernetes clusters using Docker container “nodes”.
So basically the layers are : your VM -> container hosted on yours VM's docker which is acting as Kubernetes node -> on this container there are pods -> in those pods are containers.
In kind quickstart section you can find more detailed information about image used by kind:
This will bootstrap a Kubernetes cluster using a pre-built node image. Prebuilt images are hosted at
kindest/node, but to find images suitable for a given release currently you should check the release notes for your given kind version (check withkind version) where you'll find a complete listing of images created for a kind release.
Back to your question, let's find missing containers!
On my local VM, I setup kind Kubernetes and I have installed kubectl tool Then, I created an example nginx-deployment. By running kubectl get pods I can confirm pods are working.
Let's find container which is acting as node by running docker ps -a:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1d2892110866 kindest/node:v1.21.1 "/usr/local/bin/entr…" 50 minutes ago Up 49 minutes 127.0.0.1:43207->6443/tcp kind-control-planeOkay, now we can exec into it and find containers. Note that kindest/node image is not using docker as the container runtime but crictl.
Let's exec into node: docker exec -it 1d2892110866 sh:
# ls
bin boot dev etc home kind lib lib32 lib64 libx32 media mnt opt proc root run sbin srv sys tmp usr var
# Now we are in node - time to check if containers are here:
# crictl ps -a
CONTAINER IMAGE CREATED STATE NAME ATTEMPT POD ID
135c7ad17d096 295c7be079025 47 minutes ago Running nginx 0 4e5092cab08f6
ac3b725061e12 295c7be079025 47 minutes ago Running nginx 0 6ecda41b665da
a416c226aea6b 295c7be079025 47 minutes ago Running nginx 0 17aa5c42f3512
455c69da57446 296a6d5035e2d 57 minutes ago Running coredns 0 4ff408658e04a
d511d62e5294d e422121c9c5f9 57 minutes ago Running local-path-provisioner 0 86b8fcba9a3bf
116b22b4f1dcc 296a6d5035e2d 57 minutes ago Running coredns 0 9da6d9932c9e4
2ebb6d302014c 6de166512aa22 57 minutes ago Running kindnet-cni 0 6ef310d8e199a
2a5e0a2fbf2cc 0e124fb3c695b 57 minutes ago Running kube-proxy 0 54342daebcad8
1b141f55ce4b2 0369cf4303ffd 57 minutes ago Running etcd 0 32a405fa89f61
28c779bb79092 96a295389d472 57 minutes ago Running kube-controller-manager 0 2b1b556aeac42
852feaa08fcc3 94ffe308aeff9 57 minutes ago Running kube-apiserver 0 487e06bb5863a
36771dbacc50f 1248d2d503d37 58 minutes ago Running kube-scheduler 0 85ec6e38087b7Here they are. You can also notice that there are other container which are acting as Kubernetes Components.
For further debugging containers I would suggest reading documentation about debugging Kubernetes nodes with crictl.
Please also note that on your local VM there is file ~/.kube/config which has information needed for kubectl to communicate between your VM and the Kubernetes cluster (in case of kind Kubernetes - docker container running locally).
Hope It will help you. Feel free to ask any question.
EDIT - ADDED INFO HOW TO SETUP MOUNT POINTS
Answering question from comment about mounting directory from node to local VM. We need to setup "Extra Mounts". Let's create a definition needed for kind Kubernetes:
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
# add a mount from /path/to/my/files on the host to /files on the node
extraMounts:
- hostPath: /tmp/logs/
containerPath: /var/log/pods
# optional: if set, the mount is read-only.
# default false
readOnly: false
# optional: if set, the mount needs SELinux relabeling.
# default false
selinuxRelabel: false
# optional: set propagation mode (None, HostToContainer or Bidirectional)
# see https://kubernetes.io/docs/concepts/storage/volumes/#mount-propagation
# default None
propagation: Bidirectional
Note that I'm using /var/log/pods instead of /var/log/containers/ - it is because on the cluster created by kind Kubernetes containers directory has only symlinks to logs in pod directory.
Save this yaml, for example as cluster-with-extra-mount.yaml , then create a cluster using this (create a directory /tmp/logs before applying this command!):
kind create cluster --config=/tmp/cluster-with-extra-mount.yamlThen all containers logs will be in /tmp/logs on your VM.