Comment 59 for bug 131983

Actually, idle priority is not allowed for non-root processes. So your sudo... line works, but tracker (running as non-root) cannot ionice itself to idle. There's some good explaination on the web why idle is only allowed for root (IIRC an idle I/O-process could starve a depending realtime process to death or something like that).

For now, I for my part have uninstalled tracker, as it reindexed my whole $HOME (with both some big and many small files) again and again. But i'll stay tuned and retry it when the next minor release hits the repositories.

Ciao

Martin