just answer myself. get some fix from <a href="http://audacityteam.org/forum/thread/132">http://audacityteam.org/forum/thread/132</a> lsof lives here: <a href="ftp://vic.cc.purdue.edu/pub/tools/unix/lsof/README"> ftp://vic.cc.purdue.edu/pub/tools/unix/lsof/README</a> Any decent distribution should package it so you can install via your package manager. aoss is part of the ALSA OSS compatability layer from the ALSA project. Again, should be a distro package for this. You can't use audacity if there is a sound daemon running because audacity doesn't support the broken playback-only protocols used by sound daemons. You can try the emulation scripts like $ artsdsp audacity or $ esddsp audacity but the results are likely to be poor because of the extrac conversion and latency. <div>On 6/19/06, Yuandan Zhang <<a href="mailto:yuandan.zhang@gmail.com">yuandan.zhang@gmail.com</a>> wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div> Hi, I had difficulty to use audcity. when I started audacity, I got error like this There was an error initializing the audio i/o layer, you will not be able to play or record audio Error: Host error From there, I searched google and last post on this list. there were some suggestions: I followed them and did following things prior to start audacity rm ~/.audacity use alsamixer to unmute mic use volumn-control to unmute microphone input su -c "chmod 666 /dev/dsp* " It worked shortly, but after restart this system, I can't get this work any more. It can open a mp3 file, but can't play it. when click on play botton, it says Error while opening sound device. please check the output device settings and the project sample rate. I opened up the preperfence of audacity -> Audio i/o, there is nothing to select from playback device and recording device. please offer some suggestions? Yuandan my system is 2.6.16-1.2133_FC5 #1 Tue Jun 6 00:52:14 EDT 2006 i686 i686 i386 GNU/Linux I maintain it updated </div></blockquote></div>