configure sftp on ubuntu

Assume SSH is already set up, sftp is easy to configure. It uses the same port as SSH.

Modify /etc/ssh/sshd_config, uncomment this line:

Subsystem      sftp    /usr/lib/openssh/sftp-server

add the following under this line:

Match User <username>
        ChrootDirectory <dir>
        X11Forwarding no
        AllowTcpForwarding no
        ForceCommand internal-sftp

where <username> is the fullname (not username) of the user. <dir> is the most upper directory this user can access. Then restart service, on ubuntu:

> sudo systemctl restart ssh

When login on ftp clients, the login username is the username (not fullname) of the configured user.