When setting up Kubernetes cluster with kubeadmin, an init command option is used to set up the Kubernetes control plane. Kubernetes has a number of Container images that will be used while bootstrapping a cluster.
In an environment where internet access is not reliable or when you have a restricted internet access like when using Proxy servers, or if your Kubernetes nodes doesn’t have internet access at all, it makes sense to pre-pull the container images to be used.
First you’ll need to print a list of images kubeadm will use ( on a machine with kubeadm installed).
$ sudo kubeadm config images listk8s.gcr.io/kube-apiserver:v1.17.0k8s.gcr.io/kube-controller-manager:v1.17.0k8s.gcr.io/kube-scheduler:v1.17.0k8s.gcr.io/kube-proxy:v1.17.0k8s.gcr.io/pause:3.1k8s.gcr.io/etcd:3.4.3-0k8s.gcr.io/coredns:1.6.5
The default registry used is k8s.gcr.io, you have an option to use a different registry. E.g using docker:
$ sudo kubeadm config images list --image-repository docker.iodocker.io/kube-apiserver:v1.17.0docker.io/kube-controller-manager:v1.17.0docker.io/kube-scheduler:v1.17.0docker.io/kube-proxy:v1.17.0docker.io/pause:3.1docker.io/etcd:3.4.3-0docker.io/coredns:1.6.5
This will use the latest stable version of Kubernetes. You can also specify the version of Kubernetes to use, e.g stable, latest
$ sudo kubeadm config images list --kubernetes-version latest
Pull container images with kubeadm command
If your Kubernetes machines have access to internet for pulling Container images, you can use the kubeadm command to pre-pull the required images:
------- Pull from default registry: k8s.gcr.io -------$ sudo kubeadm config images pull------- Pull from a different registry, e.g docker.io or internal -------$ sudo kubeadm config images pull --image-repository docker.io
For docker you may need to login to pull the images:
$ sudo docker loginLogin with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.Username: jmutaiPassword:WARNING! Your password will be stored unencrypted in /root/.docker/config.json.Configure a credential helper to remove this warning. Seehttps://docs.docker.com/engine/reference/commandline/login/#credentials-storeLogin Succeeded
Note that if you change a container repository, you’ll need to do the same when running init.
$ sudo kubeadm init --image-repository <registry> <options>
Pull container images with docker / podman command
For Kubernetes nodes without internet access, you’ll need to download images from you Local machine and upload the to your Kubernetes nodes.
List images to be used on machine with kubeadm
sudo kubeadm config images list
Download images locally
for image in k8s.gcr.io/kube-apiserver:v1.17.0 \k8s.gcr.io/kube-controller-manager:v1.17.0 \k8s.gcr.io/kube-scheduler:v1.17.0 \k8s.gcr.io/kube-proxy:v1.17.0 \k8s.gcr.io/pause:3.1 \k8s.gcr.io/etcd:3.4.3-0 \k8s.gcr.io/coredns:1.6.5; dosudo docker pull $image;done
If using podman:
for image in k8s.gcr.io/kube-apiserver:v1.17.0 \k8s.gcr.io/kube-controller-manager:v1.17.0 \k8s.gcr.io/kube-scheduler:v1.17.0 \k8s.gcr.io/kube-proxy:v1.17.0 \k8s.gcr.io/pause:3.1 \k8s.gcr.io/etcd:3.4.3-0 \k8s.gcr.io/coredns:1.6.5; dosudo docker pull $image;done
Save images as .tar files
# Examplemkdir ~/k8s-imagesdocker save k8s.gcr.io/kube-apiserver:v1.17.0 > ~/k8s-images/kube-apiserver.tar# Do the same for all other images
Upload saved images to Kubernetes nodes
rsync -av ~/k8s-images/* k8s-node:~/k8s-images/
Import .tar image files into Docker.
cd k8s-images/ls * | while read image; do sudo docker load < $image; done
Here is a sample load output.
# ls * | while read image; do docker load < $image; done225df95e717c: Loading layer [==================================================>] 336.4kB/336.4kB7c9b0f448297: Loading layer [==================================================>] 41.37MB/41.37MBLoaded image: k8s.gcr.io/coredns:1.6.5fe9a8b4f1dcc: Loading layer [==================================================>] 43.87MB/43.87MBce04b89b7def: Loading layer [==================================================>] 224.9MB/224.9MB1b2bc745b46f: Loading layer [==================================================>] 21.22MB/21.22MBLoaded image: k8s.gcr.io/etcd:3.4.3-0fc4976bd934b: Loading layer [==================================================>] 53.88MB/53.88MBf103db1d7ea4: Loading layer [==================================================>] 118.6MB/118.6MBLoaded image: k8s.gcr.io/kube-apiserver:v1.17.001b437934b9d: Loading layer [==================================================>] 108.5MB/108.5MBLoaded image: k8s.gcr.io/kube-controller-manager:v1.17.0ac06623e44c6: Loading layer [==================================================>] 42.1MB/42.1MBLoaded image: k8s.gcr.io/kube-scheduler:v1.17.0682fbb19de80: Loading layer [==================================================>] 21.06MB/21.06MB2dc2f2423ad1: Loading layer [==================================================>] 5.168MB/5.168MBad9fb2411669: Loading layer [==================================================>] 4.608kB/4.608kB597151d24476: Loading layer [==================================================>] 8.192kB/8.192kB0d8d54147a3a: Loading layer [==================================================>] 8.704kB/8.704kB6bc5ae70fa9e: Loading layer [==================================================>] 37.81MB/37.81MBLoaded image: k8s.gcr.io/kube-proxy:v1.17.0e17133b79956: Loading layer [==================================================>] 744.4kB/744.4kBLoaded image: k8s.gcr.io/pause:3.1
Confirm the images are imported:
# docker imagesREPOSITORY TAG IMAGE ID CREATED SIZEk8s.gcr.io/kube-proxy v1.17.0 7d54289267dc 4 weeks ago 116MBk8s.gcr.io/kube-apiserver v1.17.0 0cae8d5cc64c 4 weeks ago 171MBk8s.gcr.io/kube-controller-manager v1.17.0 5eb3b7486872 4 weeks ago 161MBk8s.gcr.io/kube-scheduler v1.17.0 78c190f736b1 4 weeks ago 94.4MBk8s.gcr.io/coredns 1.6.5 70f311871ae1 2 months ago 41.6MBk8s.gcr.io/etcd 3.4.3-0 303ce5db0e90 2 months ago 288MBk8s.gcr.io/pause 3.1 da86e6ba6ca1 2 years ago 742kB
You can then proceed with your Kubernetes installation with locally added images. Depending on the CNI you use, you may need to pull its image as well in advance if doing offline installations.
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