Further reading

• How to create users and groups from the Linux command line: https://www.techrepublic.com/article/how-to-create-users-and-groups-in-linux-from-the-command-line/
• Add a user to a group: https://www.howtogeek.com/50787/add-a-user-to-a-group-or-second-group-on-linux/
• SGID on directories: https://www.toptip.ca/2010/03/linux-setgid-on-directory.html
• What a sticky bit is and how to set it in Linux: https://www.linuxnix.com/sticky-bit-set-linux/