> Starting bitcoind with `-onlynet=onion` immediately after adding bitcoind user to debian-tor group will yield the following notice on debug.log:
>
>"tor: Authentication cookie /run/tor/control.authcookie could not be opened (check permissions)"
>
>Elaborate on the need to re-login to ensure debian-tor group has been applied to bitcoind user after:
>
> sudo usermod -a -G debian-tor username
>
>Verification can be done via `groups` command in shell.
Backport of Core PR16857
Depends of D8002