Is it possible to take an image or a snapshot of container running inside pod using kubectl?
Via docker, it is possible to use the docker commit command that creates an image of a container from which we can spawn more containers. I wanted to understand if there was something similar that we could do with kubectl.
No, partially because that's not in the kubernetes mental model of anything one would wish to do to a cluster, and partially because docker is not the only container runtime kubernetes uses. Every runtime one could use underneath kubernetes would need to support that operation, and I doubt they do.
You are welcome to do your own docker commit either by getting a shell on the Node, or by running a privileged Pod then connecting to the docker.sock via a volumeMount and running it that way
Related
I have created a new docker image that I want to use to replace the current docker image. The application is on the kubernetes engine on google cloud platform.
I believe I am supposed to use the gcloud container clusters update command. Although, I struggle to see how it works and how I'm supposed to replace the old docker image with the new one.
You may want to use kubectl in order to interact with your GKE cluster. Method of image update depends on how the Pod / Container was created.
For some example commands, see https://kubernetes.io/docs/reference/kubectl/cheatsheet/#updating-resources
For example, kubectl set image deployment/frontend www=image:v2 will do a rolling update "www" containers of "frontend" deployment, updating the image.
Getting up and running on GKE: https://cloud.google.com/kubernetes-engine/docs/quickstart
You can use Container Registry[1] as a single place to manage Docker images.
Google Container Registry provides secure, private Docker repository storage on Google Cloud Platform. You can use gcloud to push[2] images to your registry, then you can pull images using an HTTP endpoint from any machine.
You can also use Docker Hub repositories[3] allow you share container images with your team, customers, or the Docker community at large.
[1]https://cloud.google.com/container-registry/
[2]https://cloud.google.com/container-registry/docs/pushing-and-pulling
[3]https://docs.docker.com/docker-hub/repos/
I am attempting to run two separate pods using the same container image on a cluster by applying a config file. Despite there being no shared or persistent volume when both pods are active the same directory on both pods is updated with created files from the other pod and write access changes suddenly. The container being used is the jupyter-docker-stacks jupyter/minimal-notebook image being pulled directly from dockerhub. These pods running this container is created by applying a manifest. The two pods have different labels and names. A service with a unique name is created for each pod for access.
Do resources for containers persist over time on a cluster like in docker containers? I cannot find something equivalent to a --rm flag to be used alongside kubectl apply.
Thanks
If you want to delete the pod after the job is completed, you might want to apply job instead of pod. The idea of job in k8s is to launch a pod and do the job, and then the pod get stopped. For more info: https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/
$ kubectl apply -f <fileName> will create or make some changes in the pod. If you want to delete pod using apply you must use $ kubectl delete -f <fileName>
About sharing, if you have 2 separate manifest you can specify volumeMounts for each container. For more information please read the documentation depends on your needs.
Also as #Kaizhe Huang advised you can use Job if you want to execute something one time or try initContainers if you want to install something in POD before main container will be run. More about initContainers here.
You could check the dockerfile of your image. See if there are 'VOLUME' claimed. If have, maybe they share the same volume on host. Not sure, but you could check.
I would like to suspend the main process in a docker container running in a kubernetes pod. I have attempted to do this by running
kubectl exec <pod-name> -c <container-name> kill -STOP 1
but the signal will not stop the container. Investigating other approaches, it looks like docker stop --signal=SIGSTOP or docker pause might work. However, as far as I know, kubectl exec always runs in the context of a container, and these commands would need to be run in the pod outside the context of the container. Does kubectl's interface allow for anything like this? Might I achieve this behavior through a call to the underlying kubernetes API?
You could set the replicaset to 0 which would set the number of working deployments to 0. This isn't quite a Pause but it does Stop the deployment until you set the number of deployments to >0.
kubectl scale --replicas=0 deployment/<pod name> --namespace=<namespace>
So kubernetes does not support suspending pods because it's a VM kinda behavior, and since starting a new one is cheaper it just schedules a new pod in case of failure. In effect your pods should be stateless. And any application that needs to store state, should have a persistent volume mounted inside the pod.
The simple mechanics(and general behavior) of Kubernetes is if the process inside the contaiener fails kuberentes will restart it by creating a new pod.
If you also comment what you are trying to achieve as an end goal I think I can help you better.
The pods i am working with are being managed by kubernetes. When I use the docker restart command to restart a pod, sometimes the pod gets a new id and sometimes the old one. When the pod gets a new id, its state first goes friom running ->error->crashloopbackoff. Can anyone please tell me why is this happening. Also how frequently does kubernetes does the health check
Kubernetes currently does not use the docker restart command for many reasons (e.g., preserving the logs of older containers). Kubelet, the daemon on the node, creates a new container if the existing container terminated. In any case, users should not perform container lifecycle operations (e.g., stop, restart) on kubernetes-managed containers directly using docker, as it could cause unexpected behaviors.
EDIT: If you want kubernetes to restart your container automatically, set RestartPolicy in your pod spec to "Always" or "OnFailure". For more details, see http://kubernetes.io/docs/user-guide/pod-states/
I have an instance group of Container VMs running my app on a docker container.
I am trying to find a good strategy to manage the application logs for docker + MEAN + Google Cloud Compute Machines.
I can see the logs on individual containers running docker logs [container_id].
However, if I stop and start the VM I lose those logs. I also have VMs dynamically added by Auto scaler and would like to have a convenient way to access the logs.
Stack is MEAN and Logging tool is bunyan.
Is is possible to centralize or combine the logs from all VMS in one persistent location?
any suggestions?
UPDATES:
I installed fluentd agent and now I can see logs when I manually run thins on the shell: logger "some message for testing"
However, the logs from my container vm from my docker container never shows up on logs.
I still don't know how to get those docker logs to turn up on google cloud logs. It is supposed to be automatically collected.
cheers
Leo
Here is a yaml, Dockerfile and conf for a fluentd pod inside kubernetes.
Adjust the yaml to mount a disk:
https://github.com/GoogleCloudPlatform/kubernetes/tree/master/contrib/logging/fluentd-sidecar-gcp
Then adjust the config to log to the disk.
Build the container with the new configuration.
Deploy the new container.