The rest of the filesystem is accessible for reading only. Still, quoting
systemd.exec(5):
Note that restricting access with these options does not extend to submounts
of a directory that are created later on.
Our current systemd unit uses "Type = simple", so systemd does not expect tor to
fork. If the user has "RunAsDaemon 1" in their torrc, then things won't work as
expected. This is e.g. the case on Debian (and derivatives), since there we pass
"--defaults-torrc /usr/share/tor/tor-service-defaults-torrc" (that contains
"RunAsDaemon 1") by default.
The only solution I could find is to explicitly pass "--RunAsDaemon 0" when
starting tor from the systemd unit file, which this commit does.
