torcfg

$ sudo -u debian-tor /usr/bin/tor --verify-config --defaults-torrc /usr/share/tor/tor-service-defaults-torrc -f /etc/tor/torrc --RunAsDaemon 0
Dec 13 22:07:13.834 [notice] Tor 0.3.5.10 running on Linux with Libevent 2.1.8-stable, OpenSSL 1.1.1d, Zlib 1.2.11, Liblzma 5.2.4, and Libzstd 1.3.8.
Dec 13 22:07:13.834 [notice] Tor can't help you if you use it wrong! Learn how to be safe at https://www.torproject.org/download/download#warning
Dec 13 22:07:13.834 [notice] Read configuration file "/usr/share/tor/tor-service-defaults-torrc".
Dec 13 22:07:13.834 [notice] Read configuration file "/etc/tor/torrc".
Dec 13 22:07:13.838 [warn] Error setting groups to gid 124: "Operation not permitted".
Dec 13 22:07:13.838 [warn] Tor is already running as debian-tor.  You do not need the "User" option if you are already running as the user you want to be.  (If you did not set the User option in your torrc, check whether it was specified on the command line by a startup script.)
Dec 13 22:07:13.838 [warn] Failed to parse/validate config: Problem with User value. See logs for details.
Dec 13 22:07:13.838 [err] Reading config failed--see warnings above.