users-and-groups-in-linux

https://www.tecmint.com/compress-files-and-finding-files-in-linux/

https://www.tecmint.com/manage-users-and-groups-in-linux/ 

https://www.linode.com/docs/tools-reference/linux-users-and-groups/#understanding-sudo

http://www.yolinux.com/TUTORIALS/LinuxTutorialManagingGroups.html

https://www.linux.com/learn/intro-to-linux/2017/12/how-manage-users-groups-linux

https://www.digitalocean.com/community/tutorials/an-introduction-to-linux-permissions

https://wiki.archlinux.org/index.php/users_and_groups