usermod

Modifies a user account. See also: users, useradd, userdel. More information: https://manned.org/usermod.

Change a username:

sudo usermod --login {{new_username}} {{username}}

Change a user id:

sudo usermod --uid {{id}} {{username}}

Change a user shell:

sudo usermod --shell {{path/to/shell}} {{username}}

Add a user to supplementary groups (mind the lack of whitespace):

sudo usermod --append --groups {{group1,group2,...}} {{username}}

Change a user home directory:

sudo usermod --move-home --home {{path/to/new_home}} {{username}}