root@marmot:~# lvcreate -L 256M -n home-$NEW_USER lvm-marmot
root@marmot:~# mkfs.ext4 -L home-$NEW_USER /dev/lvm-marmot/home-$NEW_USER
root@marmot:~# mkdir /home/$NEW_USER
root@marmot:~# [edit /etc/fstab to mount new user space]
root@marmot:~# mount /home/$NEW_USER
root@marmot:~# useradd -k -G users,wormnet-shell -s /bin/bash $NEW_USER
root@marmot:~# passwd $NEW_USER
root@marmot:~# mkdir /home/$NEW_USER/.ssh
root@marmot:~# echo "ssh-rsa AAAB3...KD0pw== fred@foobar" > /home/$NEW_USER/.ssh/authorized_keys
root@marmot:~# chown -R $NEW_USER:$NEW_USER /home/$NEW_USER/.ssh/

If you make the users account use the shell /usr/bin/rssh and edit /etc/rssh.conf then you can create accounts that can only upload/download files rather than have a full shell - although you will still need to add them to the 'wormnet-shell' group.