Creates folder/file with second user permission on linux Centos

Question

Linux permission question:
I have one folder "test" with a permission group "test", the primary group for "test" user is "users" and the second group is "test" How to make the second group "test" to receive permission when a user "test" is create a folder or file in the /test directory?

The group "users" don't need to have access to the "test" user folder.

After the user "test" creates a new folder/file inside the "test" directory it need to be will show as following:

$ll /test drwxr-xr-x 2 test test qa/

not: $ll /test drwxr-xr-x 2 test users qa/

Answer 1

Use sticky bit setguid (an s attribute) attribute on folder. It ensures all new files or folders created in it will inherit it's rights group id. For exmaple:

 mkdir test
 sudo chown jask:root test
 sudo chmod g+s test
 touch test/test_file
 ll test/

 -rw-rw-r-- 1 jask root 0 15. pro 11.46 test_file

Similarly you can use setuid chmod u+s for inheriting owner (uid).

When used not on folders but executables it has different meaning. For more reference use https://en.wikipedia.org/wiki/Setuid

Answer 2

Solved, with "chmod g+s test" and add the user to test group. So anyone who is in the test group inheriting the GID from the top folder.