How to debug authentication failures

I’m trying to run nixos in a customized container on a rooted android phone. The systemd starts up and I’m able to get the login prompt, but login will always fail with authentication failure. Are there anyway to debug what’s going on here? I tried following the man page and add debug and audit to the pam config for login but nothing happens, no additional logs can be found in journal. According to the source code it seems some debug log will be printed to /var/run/pam-debug.log but there is no such file created.