Problem scenario
You run kubectl describe pods. You see a message in the output that says
networkPlugin cni failed to set up pod network: open /run/flannel/subnet.env: no such file or directory.
How do you fix this?
Possible Solution #1
Log into every worker node. Make sure it has /run/flannel/subnet.env with the following four lines:
FLANNEL_NETWORK=10.244.0.0/16
FLANNEL_SUBNET=10.244.0.1/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=true(This solution was adapted from https://www.programmersought.com/article/7824768991/)
Possible Solution #2
Run this: kubectl get pods. It could be that the error message shows up, but there is no problem. If the problem has since subsided, it may be ignorable.
Possible Solution #3
"More often than not, there is another issue that could be causing this error that needs to be investigated first."
(This one was taken from this Microsoft website.)