UFW config changes for NBD connections

readme

Set the default INPUT policy to ACCEPT: Edit /etc/default/ufw and set:
DEFAULT_INPUT_POLICY="ACCEPT"

Append a drop-all rule to the INPUT chain: Edit /etc/ufw/after.rules, add this line just before the final COMMIT line:
-A ufw-reject-input -j DROP

Disable UFW logging (this seems to cause issuses with Scaleway's default kernel):
ufw logging off

Enable UFW (don't forget to allow SSH traffic):
ufw allow ssh;
ufw enable

That's it, UFW is up and running, and NBD shouldn't cause issues.