Create a New User

FULL_NAME="..."
HOME_DIR="..."
USERNAME="..."

useradd -c "${FULL_NAME}" -Md "${HOME_DIR}" -s /bin/false "${USERNAME}"

With a specific UID / GID

FULL_NAME="..."
HOME_DIR="..."
USERNAME="..."
NEW_UID="..."
NEW_GID="..."

groupadd -g ${NEW_GID} "${USERNAME}"
useradd -u ${NEW_UID} -g ${NEW_GID} -Md "${HOME_DIR}" -s /bin/false "${USERNAME}"