In this post, I’ll show you how to set up secure ftp (SFTP) access to your Ubuntu server. (Instructions for Debian are very similar: leave out the sudo part and follow these steps as root:) More here
For this to work, you’ll need Ubuntu 8.10 “Intrepid”, Debian 5.0 “Lenny” or newer. In this example, mark is the user that can gain superuser rights through sudo. “peter” and a few other users are the ones I want to give sftp access to their personal folder, but not shell access or anything else.