Transmission

I run transmission-daemon on the same box I watch 1080p movies on. When transmission is downloading (or seeding) a lot of stuff, I can't watch movies since they freeze constantly. Besides, its web ui becomes slow.

Is there a way to lower priority of transmission-daemon? I'd like it to work when system is idle, like if comeone has called ionice -c 3 (idle) -p <transmission-daemon-pid>

Since you seem to have a good approach to it already (using ionice) then I take it you want to have it applied automatically, which essentially means you have to edit the startup script. Exactly what needs to be changed depends on how the script is written, since they tend to differ between certain "groupings" of distros (primarily depending on the packaging system last time I looked).