My project have 2 Yamls to create which create 2 PODS each.
Can we create a single POD with these yamls, without merging the yamls, with 2 containers ?
Thanks
Yes, you run multiple containers inside the single pod. In single YAML manifest, you can add your both containers spec and run it.
however, you cannot without merging YAML you can not run multiple containers inside one pod.
for single file example :
apiVersion: v1
kind: Pod
metadata:
name: mc1
spec:
volumes:
- name: html
emptyDir: {}
containers:
- name: 1st
image: nginx
volumeMounts:
- name: html
mountPath: /usr/share/nginx/html
- name: 2nd
image: debian
volumeMounts:
- name: html
mountPath: /html
command: ["/bin/sh", "-c"]
args:
- while true; do
date >> /html/index.html;
sleep 1;
done
more details you can also refer official document : https://kubernetes.io/docs/tasks/access-application-cluster/communicate-containers-same-pod-shared-volume/
If you don't want to merge the containers definition in the same file and in the same containers block, then no you can't.
Related
I need to copy a file inside my pod during the time of creation. I don't want to use ConfigMap and Secrets. I am trying to create a volumeMounts and copy the source file using the kubectl cp command—my manifest looks like this.
apiVersion: v1
kind: Pod
metadata:
name: copy
labels:
app: hello
spec:
containers:
- name: init-myservice
image: bitnami/kubectl
command: ['kubectl','cp','./test.json','init-myservice:./data']
volumeMounts:
- name: my-storage
mountPath: data
- name: init-myservices
image: nginx
volumeMounts:
- name: my-storage
mountPath: data
volumes:
- name: my-storage
emptyDir: {}
But I am getting a CrashLoopBackOff error. Any help or suggestion is highly appreciated.
it's not possible.
let me explain : you need to think of it like two different machine. here your local machine is the one where the file exist and you want to copy it in another machine with cp. but it's not possible. and this is what you are trying to do here. you are trying to copy file from your machine to pod's machine.
here you can do one thing just create your own docker image for init-container. and copy the file you want to store before building the docker image. then you can copy that file in shared volume where you want to store the file.
I do agree with an answer provided by H.R. Emon, it explains why you can't just run kubectl cp inside of the container. I do also think there are some resources that could be added to show you how you can tackle this particular setup.
For this particular use case it is recommended to use an initContainer.
initContainers - specialized containers that run before app containers in a Pod. Init containers can contain utilities or setup scripts not present in an app image.
Kubernetes.io: Docs: Concepts: Workloads: Pods: Init-containers
You could use the example from the official Kubernetes documentation (assuming that downloading your test.json is feasible):
apiVersion: v1
kind: Pod
metadata:
name: init-demo
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
volumeMounts:
- name: workdir
mountPath: /usr/share/nginx/html
# These containers are run during pod initialization
initContainers:
- name: install
image: busybox
command:
- wget
- "-O"
- "/work-dir/index.html"
- http://info.cern.ch
volumeMounts:
- name: workdir
mountPath: "/work-dir"
dnsPolicy: Default
volumes:
- name: workdir
emptyDir: {}
-- Kubernetes.io: Docs: Tasks: Configure Pod Initalization: Create a pod that has an initContainer
You can also modify above example to your specific needs.
Also, referring to your particular example, there are some things that you will need to be aware of:
To use kubectl inside of a Pod you will need to have required permissions to access the Kubernetes API. You can do it by using serviceAccount with some permissions. More can be found in this links:
Kubernetes.io: Docs: Reference: Access authn authz: Authentication: Service account tokens
Kubernetes.io: Docs: Reference: Access authn authz: RBAC
Your bitnami/kubectl container will run into CrashLoopBackOff errors because of the fact that you're passing a single command that will run to completion. After that Pod would report status Completed and it would be restarted due to this fact resulting in before mentioned CrashLoopBackOff. To avoid that you would need to use initContainer.
You can read more about what is happening in your setup by following this answer (connected with previous point):
Stackoverflow.com: Questions: What happens one of the container process crashes in multiple container POD?
Additional resources:
Kubernetes.io: Pod lifecycle
A side note!
I also do consider including the reason why Secrets and ConfigMaps cannot be used to be important in this particular setup.
I have a deployment that runs two containers. One of the containers attempts to build (during deployment) a javascript bundle that the other container, nginx, tries to serve.
I want to use a shared volume to place the javascript bundle after it's built.
So far, I have the following deployment file (with irrelevant pieces removed):
apiVersion: apps/v1
kind: Deployment
metadata:
...
spec:
...
template:
...
spec:
hostNetwork: true
containers:
- name: personal-site
image: wheresmycookie/personal-site:3.1
volumeMounts:
- name: build-volume
mountPath: /var/app/dist
- name: nginx-server
image: nginx:1.19.0
volumeMounts:
- name: build-volume
mountPath: /var/app/dist
volumes:
- name: build-volume
emptyDir: {}
To the best of my ability, I have followed these guides:
https://kubernetes.io/docs/concepts/storage/volumes/#emptydir
https://kubernetes.io/docs/tasks/access-application-cluster/communicate-containers-same-pod-shared-volume/
One other things to point out is that I'm trying to run this locally atm using minikube.
EDIT: The Dockerfile I used to build this image is:
FROM node:alpine
WORKDIR /var/app
COPY . .
RUN npm install
RUN npm install -g #vue/cli#latest
CMD ["npm", "run", "build"]
I realize that I do not need to build this when I actually run the image, but my next goal is to insert pod instance information as environment variables, so with javascript unfortunately I can only build once that information is available to me.
Problem
The logs from the personal-site container reveal:
- Building for production...
ERROR Error: EBUSY: resource busy or locked, rmdir '/var/app/dist'
Error: EBUSY: resource busy or locked, rmdir '/var/app/dist'
I'm not sure why the build is trying to remove /dist, but also have a feeling that this is irrelevant. I could be wrong?
I thought that maybe this could be related to the lifecycle of containers/volumes, but the docs suggest that "An emptyDir volume is first created when a Pod is assigned to a Node, and exists as long as that Pod is running on that node".
Question
What are some reasons that a volume might not be available to me after the containers are already running? Given that you probably have much more experience than I do with Kubernetes, what would you look into next?
The best way is to customize your image's entrypoint as following:
Once you finish building the /var/app/dist folder, copy(or move) this folder to another empty path (.e.g: /opt/dist)
cp -r /var/app/dist/* /opt/dist
PAY ATTENTION: this Step must be done in the script of ENTRYPOINT not in the RUN layer.
Now use /opt/dist instead..:
apiVersion: apps/v1
kind: Deployment
metadata:
...
spec:
...
template:
...
spec:
hostNetwork: true
containers:
- name: personal-site
image: wheresmycookie/personal-site:3.1
volumeMounts:
- name: build-volume
mountPath: /opt/dist # <--- make it consistent with image's entrypoint algorithm
- name: nginx-server
image: nginx:1.19.0
volumeMounts:
- name: build-volume
mountPath: /var/app/dist
volumes:
- name: build-volume
emptyDir: {}
Good luck!
If it's not clear how to customize the entrypoint, share with us your entrypoint of the image and we will implement it.
I used config map with files but i am experimenting with portable services like supervisor d and other internal tools.
we have golang binary that can be run in any image. what i am trying is to run these binary using configmap.
Example :-
We have a internal tool written in Go(size is less than 7MB) can be store in config map and we want to mount that config map inside kuberneates pod and want to run it inside pod
Question :- does anyone use it ? Is it a good approach ? What is the best practice ?
I don't believe you can put 7MB of content in a ConfigMap. See here for example. What you're trying to do sounds like a very unusual practice. The standard practice to run binaries in Pods in Kubernetes is to build a container image that includes the binary and configure the image or the Pod to run that binary.
I too faced similar issue while storing elastic.jks keystore binary file in k8s pod.
AFAIK there are two options:
Make use of configmap to store binary data. Check this out.
OR
Store your binary file remotely somewhere like in s3 bucket and pull that binary before running actual pod using initContainers concept.
apiVersion: v1
kind: Pod
metadata:
name: alpine
namespace: default
spec:
containers:
- name: myapp-container
image: alpine:3.1
command: ['sh', '-c', 'if [ -f /jks/elastic.jks ]; then sleep 99999; fi']
volumeMounts:
- name: jksdata
mountPath: /jks
initContainers:
- name: init-container
image: atlassian/pipelines-awscli
command: ["/bin/sh","-c"]
args: ['aws s3 sync s3://my-artifacts/$CLUSTER /jks/']
imagePullPolicy: IfNotPresent
volumeMounts:
- name: jksdata
mountPath: /jks
env:
- name: CLUSTER
value: dev-elastic
volumes:
- name: jksdata
emptyDir: {}
restartPolicy: Always
As #amit-kumar-gupta mentioned the configmap size constraint.
I recommend the second way.
Hope this helps.
I'm attempting to inject a ReplicationController's randomly generated pod ID extension (i.e. multiverse-{replicaID}) into a container's environment variables. I could manually get the hostname and extract it from there, but I'd prefer if I didn't have to add the special case into the script running inside the container, due to compatibility reasons.
If a pod is named multiverse-nffj1, INSTANCE_ID should equal nffj1. I've scoured the docs and found nothing.
apiVersion: v1
kind: ReplicationController
metadata:
name: multiverse
spec:
replicas: 3
template:
spec:
containers:
- env:
- name: INSTANCE_ID
value: $(replicaID)
I've tried adding a command into the controller's template configuration to create the environment variable from the hostname, but couldn't figure out how to make that environment variable available to the running script.
Is there a variable I'm missing, or does this feature not exist? If it doesn't, does anyone have any ideas on how to make this to work without editing the script inside of the container?
There is an answer provided by Anton Kostenko about inserting DB credentials into container environment variables, but it could be applied to your case also. It is all about the content of the InitContainer spec.
You can use InitContainer to get the hash from the container’s hostname and put it to the file on the shared volume that you mount to the container.
In this example InitContainer put the Pod name into the INSTANCE_ID environment variable, but you can modify it according to your needs:
Create the init.yaml file with the content:
apiVersion: v1
kind: Pod
metadata:
name: init-test
spec:
containers:
- name: init-test
image: ubuntu
args: [bash, -c, 'source /data/config && echo $INSTANCE_ID && while true ; do sleep 1000; done ']
volumeMounts:
- name: config-data
mountPath: /data
initContainers:
- name: init-init
image: busybox
command: ["sh","-c","echo -n INSTANCE_ID=$(hostname) > /data/config"]
volumeMounts:
- name: config-data
mountPath: /data
volumes:
- name: config-data
emptyDir: {}
Create the pod using following command:
kubectl create -f init.yaml
Check if Pod initialization is done and is Running:
kubectl get pod init-test
Check the logs to see the results of this example configuration:
$ kubectl logs init-test
init-test
I have created a pod with two containers. I know that different containers in a pod share same network namespace (i.e.,same IP and port space) and can also share a storage volume between them via configmaps. My question is do the pods also share same filesystem. For instance, in my case I have one container 'C1' that generates a dynamic file every 10 min in /var/targets.yml and I want the the other container 'C2' to read this file and perform its own independent action.
Is there a way to do this, may be some workaround via configmaps? or do I have to access these file via networking since each container have their own IP(But this may not be a good idea when it comes to POD restarts). Any suggestions or references please?
You can use an emptyDir for this:
apiVersion: v1
kind: Pod
metadata:
name: test-pd
spec:
containers:
- image: gcr.io/google_containers/test-webserver
name: generating-container
volumeMounts:
- mountPath: /cache
name: cache-volume
- image: gcr.io/google_containers/test-webserver
name: consuming-container
volumeMounts:
- mountPath: /cache
name: cache-volume
volumes:
- name: cache-volume
emptyDir: {}
But be aware, that the data isn't persistent during container recreations.