I am on centos7 . It is on multi user target. When i am trying to to run system-config-users ( It is installed) i am getting " system-config-users requires a currently running X server"
How to solve these problem.
Thanks in advance.

system-config-users is a graphical program so it can only run in X. You have two options:

1) If you have X on your machine, switch to the graphical target and then run the program.

2) Use command line tools like usermod and groupmod.

Thanks for the reply. Would you please elaborate the first point? I do have graphical target installed in my system. Does that means i also have X server running in my system?
I can switch into graphical mode and use the utility that i know. Actually my query was "is there a way i could use only the system-user-config utility while i am in multi-user target without booting into graphical mode?"

I am aware of the command line utilities for managing users.
Thnaks.

I haven't used systemd for a while, but as far as I can remember, the multi-user target is command-line only and the graphical target starts a display manager which switches on X. You can check this by using the command ps ax|grep X after booting to each target. This will tell you if X is running or not.

You can't use any graphical program outside the X environment. But it is possible that there is a similar utility to system-user-config that uses ncurses.

No. It is impossible to run an X11 *client* (which system-user-config is) withOUT any X11 *server*.
https://en.wikipedia.org/wiki/X_Window_System

I would strongly encourage you to familiarize yourself with both methods of doing these tasks: "graphical GUIs," and "the command line."

Most of the time, you'll be working with "headless" virtual servers which do not have "X" installed because there is no perceived need for it. You will manage those servers with command-line commands.

Now, that having been said, it is also possible (just, "uncommon") to use "X" to control a headless server or a virtual machine ... even one that doesn't have a graphics-card. Unlike Microsoft Windows with its kludgy, bitmap-scraping-based solution for remote graphics, "X" is a client/server windowing system. You can connect to an "X" server located anywhere. (On your own computer, there's actually both an "X Server" and an "X Client" program running at the same time.) Some companies use this, but most do not.

While it is very convenient to initially use graphic tools to accomplish these things, during your self-education it is quite important that you understand that "there's more than one way to do it," and that you are equally comfortable using both.