Como tenho o Plex Media Server rodando com meu usuário no meu NAS, mesmo tendo meu usuário no grupo transmission, ele não estava conseguindo pegar os novos arquivos baixados pelo transmission.

Desta forma, resolvi mudar o usuário com o qual o daemon do transmission é executado, abaixo segure o procedimento:

# cp /usr/lib/systemd/system/transmission.service /etc/systemd/system/
# vim /etc/systemd/system/transmission.service

Mude:
User=transmission
Para:
User=leandrocarvalho


# cp /usr/lib/tmpfiles.d/transmission.conf /etc/tmpfiles.d/
# vim /etc/tmpfiles.d/transmission.conf

Mude:
d /run/transmission - transmission transmission -
Para:
d /run/transmission 0755 leandrocarvalho transmission - -


# systemd-tmpfiles –clean –create /etc/tmpfiles.d/transmission.conf
# cp -pau /var/lib/transmission/.config/transmission-daemon /home/leandrocarvalho/.config/
# chown leandrocarvalho:transmission -R /home/leandrocarvalho/.config/transmission-daemon/

$ vim .config/transmission-daemon/settings.json

Mude:
"incomplete-dir": "/var/lib/transmission/Downloads",
Para:
"incomplete-dir": "/home/leandrocarvalho/Downloads",


# systemctl daemon-reload
# systemctl disable transmission
# systemctl enable transmission

# ps aux | grep transmission | grep -v grep | tr -s ” ” | cut -d ” ” -f 2 | xargs kill -9
# rm /run/transmission/transmission.pid
# systemctl start transmission