Users and Groups Management in Linux

Add a user to a group

# "sudo" group in this example and user "dev"
Syntax:
usermod -aG <group> <user>

Example:
sudo usermod -aG sudo dev

Add a user to multiple groups

Syntax:
usermod -aG <groups_seperated_with_commas> <user>

Example:
sudo usermod -aG sudo,network,wheel,power,kvm dev

Remove a user from a group

# "sudo" group in this example and user "dev"
Syntax:
gpasswd -d <user> <group>

Example:
sudo gpasswd -d dev sudo