How to do this on Debian ?

rahulks

create an account for the user where the user can have access to only his folder at /home.

hostnoob

This should work. Add this to /etc/ssh/sshd_config and restart sshd

Match User username
    ChrootDirectory /home/username/

This will disable SSH access for them too

Match User username
    ChrootDirectory /home/username/
    ForceCommand internal-sftp

MuZo

More in-depth blocking

 Match User username
   ChrootDirectory %h
   ForceCommand internal-sftp
   AllowTcpForwarding no
   PermitTunnel no
   X11Forwarding no

Also to prevent a normal login on the machine

usermod -s /usr/bin/false username