How to pull image from dockerhub in kubernetes? - docker

Question

I am planning to deploy an application in my kubernetes-clustering infra.
I pushed image to dockerhub repo. How can I pull image from dockerhub?

Answer 1

One line command to create a Docker registry secret
kubectl create secret docker-registry regcred --docker-username=<your-name> --docker-password=<your-pword> --docker-email=<your-email> -n <your-namespace>
Then you can use it in your deployment file under spec
spec:
containers:
- name: private-reg-container-name
image: <your-private-image>
imagePullSecrets:
- name: regcred
More details:
https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/#create-a-secret-in-the-cluster-that-holds-your-authorization-token

Answer 2

Kubernetes run docker pull pseudo/your-image:latest under the hood. image field in Kubernetes resources is simply the docker image to run.
spec:
containers:
- name: app
image: pseudo/your-image:latest
[...]
As the docker image name contains no specific docker registry url, the default is docker.io. Your image is in fact docker.io/pseudo/your-image:latest
If your image is hosted in a private docker hub repo, you need to specify an image pull secret in the spec field.
spec:
containers:
- name: app
image: pseudo/your-image:latest
imagePullSecrets:
- name: dockerhub-credential
Here is the documentation to create the secret containing your docker hub login: https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/

Answer 3

using docker pull or kubectl set image
example yaml deployment
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
labels:
app: nginx
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.14.2
ports:
- containerPort: 80
start container and show status deployment with kubectl get deployments
result
NAME READY UP-TO-DATE AVAILABLE AGE
nginx-deployment 3/3 3 3 18s
and now update image in kubernetes using set image
kubectl set image deployment/nginx-deployment nginx=nginx:1.16.1
and show status update image with rollout
kubectl rollout status deployment/nginx-deployment
Note: ngnix is name of container ->name
containers:
- name: nginx
image: nginx:1.14.2
nginx:1.16.1 is image version in docker hub, is recommendable change version for update
if you decided remove update and rollback to the previous revision, use rollout undo
kubectl rollout undo deployment/nginx-deployment
for more information, use the documentation

Answer 4

Create a docker registry secret:
#!/bin/bash
for ns in $(kubectl get namespaces |grep -v NAME|awk '{print $1}')
do
kubectl create secret docker-registry docker.registry \
--docker-username=<MyAccountName> \
--docker-password='MyDockerHubPassword' -n $ns
done
Patch all the dynamic service accounts in all the namesapces with the secret you created in step 1
for ns in $(kubectl get namespaces|grep -v NAME|awk '{print $1}')
do
for sa in $(kubectl -n $ns get sa|grep -v SECRETS|awk '{print $1}')
do
kubectl patch serviceaccount $sa -p '{"imagePullSecrets": [{"name": "docker.registry"}]}' -n $ns
if [ $? -eq 0 ]; then
echo $ns $sa patched
else
echo Error patching $ns $sa
fi
done
done
You can patch only specific namespaces, if you wish.
Let me know how it goes.