How to create a user jail
Each user can manage the files in his home directory and in a shared area. He can't access any other portion of the filesystem.
Set the shell of every user to scponly
Create the shared area and set the correct permissions
# mkdir /var/share
# chown root.users /var/share
# chmod 0770 /var/share
Create a mount point for the shared area in each home directory
# mkdir /home/$user/share
Mount the shared area
# mount --bind /var/share /home/$user/share
