Symptom: After fresh installation of Ubuntu 12.04/14.04 Desktop, microphone on rear pink jack not working.
No sound input for Skype or Sound Recorder.
Solution 1A: I have Googled for an hour, some recommended installing PulseAudio Volume Control to select correct input device.
sudo apt-get install pavucontrol
There are 3 interface shown in Input Devices:
Rear microphone (Unplugged)
Line in (Unplugged)
The problem is that the jack detection is wrong. The rear microphone is actually plugged and the front one is not.
When I select Rear microphone (Unplugged) as input, Skype and everything works, but do not survive reboot.
Because Ubuntu selected the “plugged in” device as default again on boot.
Solution 1B: Just Google some more for how to disable or fix jack detection.
Finally found a Community source recommends a tool hda-jack-retask,
which can override jack detection status. (Actually disable jack detection)
sudo apt-get install alsa-tools-gui
Launch HDAJackRetask from Dash, check Advanced Override.
And changed the Jack Detection or Pink Mic, Rear side to Not present.
Apply and see if PulseAudio Volume Control now show Rear microphone as plugged.
If yes, click Install Boot Override to make it permanent.
Now the audio should work and survive reboots!
My Environment: Asus P5K-E (SoundMAX ADI 1988B)+ Ubuntu 14.04 Desktop 64bit
But it should work virtually every setup with the same problem.