/etc/group, How this update starts functioning without restarting the system in Unix?
Is there any command we need to run?
If you are modifying real-person group affiliations, they need to just log out and log back in.
If you are changing group permissions for a system-like account (e.g. mysql, httpd) you'd have to restart the relevant daemons, but it is sometimes hard to know all the processes that need the new GIDs which are only applied when the process is started. Rebooting will ensure that all the proper processes are started with the new GIDs.