joyin@joyin:~$ systemctl status mongod
× mongod.service - MongoDB Database Server
Loaded: loaded (/lib/systemd/system/mongod.service; disabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Mon 2022-08-29 14:55:44 IST; 6s ago
Docs: https://docs.mongodb.org/manual
Process: 41404 ExecStart=/usr/bin/mongod --config /etc/mongod.conf (code=exited, status=217/USER)
Main PID: 41404 (code=exited, status=217/USER)
CPU: 4ms
Aug 29 14:55:44 joyin systemd[1]: Started MongoDB Database Server.
Aug 29 14:55:44 joyin systemd[41404]: mongod.service: Failed to determine user credentials: No such process
Aug 29 14:55:44 joyin systemd[41404]: mongod.service: Failed at step USER spawning /usr/bin/mongod: No such process
Aug 29 14:55:44 joyin systemd[1]: mongod.service: Main process exited, code=exited, status=217/USER
Aug 29 14:55:44 joyin systemd[1]: mongod.service: Failed with result 'exit-code'.
Does mongod user exist?
Check this thread