Unix configuration is the process of tailoring a freshly installed version of Unix to your particular environment. Each Unix system may do that differently.
ifconfig -a
Unix / Linux are both file based operating systems. The majority of configuration can be amended by system configuration files, although as the systems have developed more and more of this is automated and hidden from the user. User configuration files will normally reside under the /etc directory.
Ifconfig
Unix systems are highly modular. Most programs can be swapped out with a replacement just by replacing the binary. Configuration files are usually in plaintext format, although their formats can vary.
Configuration files are typically stored in the /etc directory. They can, of course, be anywhere the implementer wishes them to be as long as the process knows where to find them.
You don't mention what you are looking for in terms of a "running configuration file". In Unix/Linux there are many of these. Most of them can be found in the /etc directory or its subdirectories but not all of them are located in /etc.
in GUI network manager in CLI ifconfig
It is isn't a configuration difference to go between single user and multi-user modes in Unix. You use a different 'run' level for that. The 'init' levels can determine whether you are operating in a single user mode or a multiple user mode. Single user mode is usually reserved for system administration.
Ifconfig stands for interface configuration. It is a system administration utility in Unix-like operating systems to configure, control and query TCP/IP network interface parameters from a command line interface or in system configuration scripts.
No files are actually "invisible." However, certain files may not be displayed by default as a convenience to the user. These are setting / configuration files for programs in the user's directory.
Most of the Unix command names are short, single words in lowercase. The commands are basically programs written in C. Traditionally, Unix system programs are stored in directories called /bin and /usr with additional programs usually used only by system administrators in /etc and /usr Many versions of Unix also have programs stored in /usr
UUCP is the abbriviation of Unix to Unix copy. It is worldwide email system called UUCP or Unix to Unix copy.This email system was developed for the operating system called Unix.