hosts file - ScottKirvan/WSL GitHub Wiki
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I thought I had this figured out, but I'll have to do more work on it.
It looks like windows is using IPv6 or something to resolve hosts, and this isn't translating to WSL and host names aren't resolving.
I do know that you can't just add your hostname/ip to /etc/hosts, because that file is overwritten (when?) with the contents from %WINDIR%\System32\drivers\etc\hosts (aka. c:\Windows\System32\drivers\etc\hosts).