I want to create a new user to run a service on the system but don't want to have
/home and other configuration files for it. Like there is a user for postgres but it doesn't have any
By default the command useradd doesn't create home directories, but for a daemon I recommend you to use the system option and change the shell to a non-existent one so no one can login with said account (in ssh for example):
sudo useradd -r -s /bin/false USERNAME
You can see all the options with
man useradd and
man groupadd if you want to create a group for the user too.
adduser --system --no-create-home USERNAME or simply have a look at the
man adduser which claims to be a "friendlier front end to the low level tools like useradd...".
I needed something similar - a new user without login privileges and tied to a system service. However, the answer by Clausi creates a user with the primary group as 'nogroup', which wasn't really desirable.
adduser --system --no-create-home --group USERNAME creates a system group with the same name as the user and associates it with the user as the primary group. This can then be verified by using the
groups USERNAME or the
id USERNAME command.