Method of changing group password policy(group ↔ gshadow)
□ If the group password policy is changed to gshadow, each group's password of group file is changed to x
□ grpconv : It is linux command to change password policy(group → gshadow)(The /etc/gshadow file is created)
□ grpunconv : It is linux command to change password policy(gshadow → group)(The /etc/gshadow file is deleted)
It also posted at : http://cysecguide.blogspot.com/2016/09/method-of-changing-group-password.html