How is user auditing done on Linux?

Question

linux

Is there any list of regular users (system and those needed for services and programs)
for web servers and so on.
I need to somehow delete all users that are not needed but leave the system ones (on different systems they are called differently and with different uids)
How did you usually do it before with such tasks?

Answer 1

System users have uid less than a certain number. In Linux it is 500, in my opinion, in FreeBSD it is 1000. All users with uid below this number are system or daemons, above are normal users (although daemons can also create a user with uid above the limit).

Answer 2

First, by searching for files owned by the user:
find / -user some_user

Answer 3

cat /etc/passwd | sed 's/\:.*//'

Answer 4

I need to somehow delete all users that are not needed

If you have a "not needed" criterion, what prevents you from using it?