Runner&Geek

Check out you have ffmpeg installed:

yum install ffmpeg

Type this simple command:

ffmpeg -i inputVideo.flv -ar 44100 -ab 160k -ac 2  outputAudio.mp3

Change inputVideo.flv with the path/name of your video file source.

Change outputAudio.mp3 with path/name of you final audio file.

Enjoy easness of linux