Information
The usermod command can be used to specify which group the root account belongs to. This affects permissions of files that are created by the root account.
Using GID 0 for the root account helps prevent root -owned files from accidentally becoming accessible to non-privileged users.
Solution
Run the following command to set the root user's GID to 0 :
# usermod -g 0 root
Run the following command to set the root group's GID to 0 :
# groupmod -g 0 root
Remove any users other than the root user with GID 0 or assign them a new GID if appropriate.