Add a user

sudo adduser <name>

password will be asked for.

Allow a user to use sudo

sudo visudo

find the line:

root    ALL=(ALL:ALL) ALL.  

add the new user thus:

bob   ALL = NOPASSWD: ALL

Add a user to groups

sudo usermod newuser_name -a -G pi,adm,dialout,cdrom,sudo,audio,video,plugdev,games,users,input,netdev,spi,i2c,gpio

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Resources
LINUX USERS
Adding new user with SUDO permission