shadow-utils package.
Add or remove users to groups.
If you are the user, you have to logout/login again for changes to take effect.
Change primary group of user u to g:
g=1000
sudo usermod -g "$g" "$u"
Sets exactly the supplementary groups of user u. Remove from non listed ones:
sudo usermod -G "$g" "$u"
Append (-a) groups g to supplementary groups of user u:
sudo usermod -aG "$g" "$u"
Change home directory of user u to d. The old contents are not moved:
sudo usermod -d "$d" "$u"
Also move home directory contents to the new home:
sudo usermod -md "$d" "$u"