Tente isto:
mkdir /your_path/progress
mkdir /your_path/completed
sudo usermod -a -G debian-transmission your_user
chgrp debian-transmission /your_path/progress
chgrp debian-transmission /your_path/completed
chmod 770 /your_path/progress
chmod 770 /your_path/completed
sudo service transmission-daemon stop
sudo adduser your_user debian-transmission
sudo nano /etc/init.d/transmission-daemon
sudo chown your_user -R /var/lib/transmission-daemon/info/
sudo chown your_user -R /your_path/progress
sudo chown your_user -R /your_path/completed
sudo chown your_user -R /etc/transmission-daemon/settings.json
E altere o arquivo: sudo nano /etc/transmission-daemon/settings.json
"rpc-whitelist": "127.0.0.1" > "rpc-whitelist": "*.*.*.*",
"rpc-password": "password" > "rpc-password": "your_password",
"download-dir": "/var/lib/transmission-daemon/downloads" > "download-dir": "/your_path/completed"
"incomplete-dir": "/var/lib/transmission-daemon/downloads" > "incomplete-dir": "/your_path/progress"
Basta reiniciar o daemon:
service transmission-daemon start