I need to create a service for a web server called daphne I would like to know what are the correct linux permissions for this. or if exists a general rule for whatever systemd service?
Any local user can read the definition of any systemd system unit through the DBus interface (for example using
systemctl show), unless you have a custom DBus policy in place to prevent this.
Making the unit file not world-readable thus makes no sense and systemd will print a warning if applicable. Similarly, it will also warn if the unit file is marked executable.
Unless you want the unit file to be editable for a particular (non-root) user or group, stick to the same convention used for most other system files: 0644 root:root.