From Linux Change Default User Home Directory While Adding A New User:
Simply open this file using a text editor, type:
vi /etc/default/useradd
The default home directory defined by HOME variable, find line that read as follows:
HOME=/home
Replace with:
HOME=/iscsi/user
Save and close the file. Now you can add user using regular useradd command:
# useradd vivek # passwd vivek
Verify user information:
# finger vivek