Create a new group
groupadd -g 54321 oracle
Create a new user
useradd -c "Operate Oracle DB" -m -d /home/oracle -g oracle -G sudoers,weblogic,orainstall -s /bin/bash -u 54321 oracle
useradd -u 54321 -g oracle oracle
Add user to a group
usermod -g sudoers oracle
usermod -a -G sudoers oracle
Delete user
userdel oracle
Delete group
groupdel oracle
Modify user
usermod
Modify group
groupmod