You can use gpasswd command as follows, # gpasswd -M user1,user2,user3,.....,user24 group_name Orelse the below script may help you.....

# !/bin/sh for USER in user1 user2 user3 user4 .... user24; do usermod -G group_name $USER done

Jus run this script, it will add the respective users to that group...!!!!