Configuring Ansible
How the cluster is upgraded
It can be instructive to analyzewhathappens in the cluster during the update. Then run the update command from the SA and, in another terminal connected to a cluster node, watch live what happens inside it. Run the command
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$ watch -x kubectl get pod,node -o wide -A
# The following screen will appear, which updates periodically
Every 2.0s: kubectl get pod,node -o wide -A node1: Tue Mar 9 17:18:01 2021
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
default pod/netchecker-agent-hostnet-l6s5x 1/1 Running 0 25h 192.168.100.18 node1
default pod/netchecker-agent-hostnet-rf5jl 1/1 Running 0 25h 192.168.100.23 node2
default pod/netchecker-agent-hostnet-sc5h7 1/1 Running 0 25h 192.168.100.25 node3
default pod/netchecker-agent-kqsz7 1/1 Running 0 25h 10.233.90.3 node1
default pod/netchecker-agent-lp5pf 1/1 Running 0 25h 10.233.92.2 node3
default pod/netchecker-agent-z7vb5 1/1 Running 0 25h 10.233.96.2 node2
default pod/netchecker-server-f98789d55-xr6n9 1/1 Running 2 24h 10.233.96.8 node2
kube-system pod/calico-kube-controllers-596bd759d5-x2zqc 1/1 Running 0 24h 192.168.100.23 node2
kube-system pod/calico-node-772q2 1/1 Running 0 25h 192.168.100.23 node2
kube-system pod/calico-node-lnh5z 1/1 Running 0 25h 192.168.100.25 node3
kube-system pod/calico-node-zcqjh 1/1 Running 0 25h 192.168.100.18 node1
kube-system pod/coredns-657959df74-7289c 1/1 Running 0 24h 10.233.96.7 node2
kube-system pod/coredns-657959df74-rtl2d 1/1 Running 0 24h 10.233.90.4 node1
kube-system pod/dns-autoscaler-b5c786945-brq6n 1/1 Running 0 24h 10.233.90.5 node1
kube-system pod/kube-apiserver-node1 1/1 Running 0 25h 192.168.100.18 node1
kube-system pod/kube-controller-manager-node1 1/1 Running 0 25h 192.168.100.18 node1
kube-system pod/kube-proxy-67lvh 1/1 Running 0 24h 192.168.100.18 node1
kube-system pod/kube-proxy-whqwb 1/1 Running 0 24h 192.168.100.25 node3
kube-system pod/kube-proxy-zs6kf 1/1 Running 0 24h 192.168.100.23 node2
kube-system pod/kube-scheduler-node1 1/1 Running 0 25h 192.168.100.18 node1
kube-system pod/metrics-server-5cd75b7749-d2594 2/2 Running 0 24h 10.233.90.6 node1
kube-system pod/nginx-proxy-node2 1/1 Running 0 25h 192.168.100.23 node2
kube-system pod/nginx-proxy-node3 1/1 Running 0 25h 192.168.100.25 node3
kube-system pod/nodelocaldns-hj5t8 1/1 Running 0 25h 192.168.100.18 node1
kube-system pod/nodelocaldns-j7zvh 1/1 Running 0 25h 192.168.100.23 node2
kube-system pod/nodelocaldns-jqbx7 1/1 Running 0 25h 192.168.100.25 node3
NAMESPACE NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE
node/node1 Ready control-plane,master 25h v1.20.4 192.168.100.18 <none> CentOS Linux 8
node/node2 Ready <none> 25h v1.20.4 192.168.100.23 <none> CentOS Linux 8
node/node3 Ready <none> 25h v1.20.4 192.168.100.25 <none> CentOS Linux 8 |
The nodes are not updated at the same time, but in turn. The node being updated changes its STATUS to Ready, SchedulingDisabled. As long as it remains in this state, you will notice that all the Pods implemented on it are eliminated and moved to the other available nodes. Once the update is finished, it will return to Ready and move on to the next node.