So I'm working on a server from home.

I do a cat /sys/class/net/eth0/operstate and it says unknown despite the interface being obviously up, since I'm SSH'ing into the box.

I try to explicitely set the interface up to force the status to say up with ip link set eth0 up. No joy, still unknown.

Hmm... maybe I should bring it down and back up.

So I do ip link set eth0 down and... I drive 15 miles to work to do the corresponding ip link set eth0 up

50 years using Unix and I'm still doing this... 😥