Editing File-system permissions (section)

==User private group==
Some systems diverge from the traditional POSIX model of users and groups by creating a new group&nbsp;– a "user private group"&nbsp;– for each user. Assuming that each user is the only member of its user private group, this scheme allows an umask of 002 to be used without allowing other users to write to newly created files in normal directories because such files are assigned to the creating user's private group. However, when sharing files is desirable, the administrator can create a group containing the desired users, create a group-writable directory assigned to the new group, and, most importantly, make the directory setgid. Making it setgid will cause files created in it to be assigned to the same group as the directory and the 002 umask (enabled by using user private groups) will ensure that other members of the group will be able to write to those files.<ref>{{cite web |last1=Epstein |first1=Brian |title=The How and Why of User Private Groups in Unix |url=https://security.ias.edu/how-and-why-user-private-groups-unix |website=security.ias.edu |publisher=Institute for Advanced Study Network Security |access-date=5 August 2014 |archive-date=8 August 2014 |archive-url=https://web.archive.org/web/20140808054151/https://security.ias.edu/how-and-why-user-private-groups-unix |url-status=dead }}</ref><ref>{{cite web |title=Red Hat Enterprise Linux 7 System Administrator's Guide, 4.3.4 Creating Group Directories |url=https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/ch-managing_users_and_groups#s2-users-tools-groups-directories |website=Red Hat Customer Portal |publisher=Red Hat}}</ref>