i'm running a redhat 7.3 box and i was wondering if there is a way i can limit the users who are allowed ftp and ssh access to the system by creating a "grant access" list of users. i don't want to create a "deny access" list since it would be prohibitively long. the lists for ftp and ssh access would not necessarily be the same, so i want to maintain two seperate lists. from my research i think the answer i am looking for involves using PAM, but i'm not sure and i have no previous experience using PAM. can anyone offer any help? also i am not married to using PAM if there is a better solution. thanks.

Have a look at the docs for PAM module "pam_listfile".