BT download use Raspberry Pi

install Transmission

$ sudo apt-get install transmission-daemon

config
$ cd /etc/transmission-daemon
$ sudo cp settings.json settings.json.sbak
$ sudo vi settings.json
"download-dir": "/home/oopsmonk/BT-Download"
"rpc-whitelist": "*.*.*.*"
"rpc-username": "oopsmonk"
"rpc-password": "web-login-pwd"

change permission on download folder.
$ chmod 777 /home/oopsmonk/BT-Download

The torrent file location
/var/lib/transmission-daemon/info/torrents/

test:
http://RaspberryPi-ip:9091

WebGUI use HTTP port

$ sudo install nginx
$ sudo vi /etc/nginx/sites-available/default
server{
        #listen   80; ## listen for ipv4; this line is default and implied
        #listen   [::]:80 default_server ipv6only=on; ## listen for ipv6
...
        location /transmission {
                proxy_pass http://127.0.0.1:9091/transmission;
        }
...
}
$ sudo service nginx restart

Test:
http://ip/transmission/web/

Reference:
Setting Up Transmission’s Web Interface
Linux防健忘日誌No.69-Ubuntu 12.04 安裝及設定transmission-daemon