sshd_config
Match User user1
ChrootDirectory /dir1
ForceCommand internal-sftp
AllowTcpForwarding no
X11Forwarding no
Create a user in the passwd file with the home dir of the above and /bin/false for shell.
chmod -R 755 /dir1
cd dir1; chmod -R 775 *
chown -R root:dba /dir1