To reproduce the problem:
1, see the general user identity information
[test1@localhost ~]$ id
uid=1005(test1) gid=1009(test1) groups=1009(test1) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
2, root root ordinary users add Group
[root@localhost ~]# gpasswd -a test1 root
Adding user test1 to group root
3, see the general user identity information
[test1@localhost ~]$ id
uid=1005(test1) gid=1009(test1) groups=1009(test1) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
Here you can see the user belongs to the group has not changed, naturally, it will not have the corresponding authority
Problem Solution:
The first way: newgrp root command execution
[test1@localhost ~]$ newgrp root
[test1@localhost ~]$ id
uid=1005(test1) gid=0(root) groups=0(root),1009(test1) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
You can see the user belongs to the group changed much, where it has been set permissions