Macro 32 Ramblings

From: https://github.com/kubernetes/kubeadm/issues/338

1. Replace IP in kuberenets configs.

oldip=192.168.1.9
newip=10.20.2.210 

cd /etc/kubernetes 

# see before 
find . -type f | xargs grep $oldip

# modify files in place 
find . -type f | xargs sed -i "s/$oldip/$newip/" 

# see after 
find . -type f | xargs grep $newip

2. backup /etc/kubernetes/pki

mkdir ~/k8s-old-pki
cp -Rvf /etc/kubernetes/pki/* ~/k8s-old-pki

3. Identify certs in /etc/kubernetes/pki that have the old IP address as an alt name (this could be cleaned up)

cd /etc/kubernetes/pki
for f in $(find -name "*.crt"); do 
  openssl x509 -in $f -text -noout > $f.txt;
done
grep -Rl $oldip .
for f in $(find -name "*.crt"); do rm $f.txt; done

4. identify configmap in the kube-system namespace that referenced the old IP, edit them:

# find all the config map names
configmaps=$(kubectl -n kube-system get cm -o name | \
  awk '{print $1}' | \
  cut -d '/' -f 2)

# fetch all for filename reference
dir=$(mktemp -d)
for cf in $configmaps; do
  kubectl -n kube-system get cm $cf -o yaml > $dir/$cf.yaml
done

# have grep help you find the files to edit, and where
grep -Hn $dir/* -e $oldip

# edit those files, in my case, grep only returned these two:
kubectl -n kube-system edit cm kubeadm-config
kubectl -n kube-system edit cm kube-proxy

5. change the IP address (via cli or gui for your distro)

6. Run the following command to renew all the Kubernetes certificates:

kubeadm alpha certs renew all

7. restart kubelete and docker

sudo systemctl restart kubelet
sudo systemctl restart docker

8. copy over the new config

sudo systemctl restart kubelet
sudo cp /etc/kubernetes/admin.conf $HOME/.kube/config

9. I rebooted for good measure.