My sound stopped working today, how can I fix it?

HUZZAH

Right. arecord was the dodgy looking element here that I eventually found through fusering the sound files (see my question for my process). But I couldn't find what was causing arecord to start as root on boot. Here's how I did that:

1. Run pstree | less
2. In that, type /arecord and press return to find the arecord process.
3. Press up once and you'll see its parent. In my case this was randomsound.

I installed randomsound a few days ago to generate extra entropy (for regenerating /dev/random) using my sound card. I had completely forgotten it was installed and I guess this was the first time I restarted since installing it.

In short sudo apt-get remove randomsound fixed it. PulseAudio can now grab my sound card and I can listen to some trashy europop while I work.

It happens to me a lot while experimenting that pulseaudio goes bananas for obscure reasons. I keep a second user on my host that I use to cross-check if the problem is system related or user related: in the first case both users will show problems, in the latter only one or the other. If the problem is user dependent, then it will be something wrong in the home folder. With pulse audio is then ~/.pulse or ~/.config/pulse. renaming those, as for example _broken, allows pulseaudio to regenerate them correctly if you logout and back in. It work most of the time with me.