If you've installed an FTP daemon on your Ubuntu server, you'll have probably set it up so that users are rooted to their own FTP directory on the server. But what if you'd like an FTP user to have access to other directories on the server? A symbolic link sounds like it would work, but I'm afraid it won't. You'll have to mount the folder you're interested in to the user's FTP folder.
Assume that we've got a user called "russell" and you've set up your FTP so that he has his own FTP folder at /var/ftp/russell/. Also assume that you want to give him access to the /var/www/ folder so that he can update the web sites on your server.
We're going to mount a folder into a subdirectory in his FTP directory, so create a suitable directory for that:
$ cd /var/ftp/russell$ mkdir www
Now we mount the /var/www directory into /var/ftp/russell/www/:
$ mount --bind /var/www /var/ftp/russell/www