Who ever creates the files/directories on a data group owner should automatically be in the...

1. chmod g+s /data

2. Verify using: ls -ld /data

Permission should be like this: drwxrws--- 2 root sysadmin 4096 Mar 16 18:08 /data

If SGID bit is set on directory then who every users creates the files on directory group owner automatically the owner of parent directory. To set the SGID bit: chmod g+s directory To Remove the SGID bit: chmod g-s directory