Users and groups - ArchWiki - Arch Linux
https://wiki.archlinux.org/title/UserChanging a username is safe and easy when done properly, just use the usermod command. If the user is associated to a group with the same name, you can rename this with the groupmod command. Alternatively, the /etc/passwd file can be edited directly, see #User database for an introduction to its format. Also keep in mind the following notes: