Hello,

There are already a few days since I'm trying to debug this situation. No much experience either.

The system install is a few months old, and it worked fine. I was playing with the system, so I don't know what really caused the problem, a kernel update, an NVidia driver installation...

Symptoms: no sound in the speakers

Gnome 3 Sound Settings
- Choose a device for sound output:
-- Dummy Output

Usually after a restart the list above is populated with the real sound devices and the sound works.
The next day the problem might come back again. If not, some other day.

[adi@localhost tmp]$ alsa-info
ALSA Information Script v 0.4.64
--------------------------------

This script visits the following commands/files to collect diagnostic
information about your ALSA installation and sound related hardware.

dmesg
lspci
lsmod
aplay
amixer
alsactl
/proc/asound/
/sys/class/sound/
~/.asoundrc (etc.)

See '/usr/sbin/alsa-info --help' for command line options.

/usr/sbin/alsactl: save_state:1595: No soundcards found...
cat: /tmp/alsa-info.aigKActD3d/alsactl.tmp: No such file or directory
Automatically upload ALSA information to www.alsa-project.org? [y/N] : y
Uploading information to www.alsa-project.org ... Done!

Your ALSA information is located at http://www.alsa-project.org/db/?f=bb...d853ee4c2f8765

Thank you.

Sometimes, if I boot the system, I get something like "Updating" and after a few seconds it restarts itself. After the restart I log in but I see some differences. If I want to mount an USB drive, it asks for root password. If I want to shut down, it asks for root password. The sound is not working.
If I restart and I can mount an usb drive or poweroff the computer without entering root credentials, also the sound is working.

Also, In the Gnome 3 upper right menu I have always the option "Install Updates & Restart". Even after I click this option and restart, it's always there.

It might help if you describe which distro you are using.
Coz, you know, they vary in how they do things.

Also, recently, distros have started using a thing called Pulseaudio, which I generally find to be a pain.

To see if Pulseaudio is running, type :-

pgrep pulse

If you get something like :-

1808 /usr/bin/pulseaudio --start --log-target=syslog
1819 /usr/libexec/pulse/gconf-helper

Then, Pulseaudio is running.

You might then try looking to see if you have something called Pulseaudio Volume Control installed. This is an app that manages Pulseaudio. That might help.

Also, sometimes if you have more than one audio device installed, the system may get confused. For example, if I have my webcam connected when I boot the system, my sound stops working. I'm too lazy to fix it properly, so I just disconnect the webcam and boot again. Then the system finds my sound card and sound starts working again.

So, you might try removing all the USB thingys connected and see if that makes a difference.

Not knowing your system, I'm just guessing, of course.

Ok, sorry. I didn't read the alsa-info stuff.

You're running CentOS 7 and Pulseaudio.

To check if you have Pulseaudio Volume Control installed, run

rpm -qa | grep pavucontrol

If it's not installed, you might try :-

yum install pavucontrol

I'm not running CentOS 7 myself, so I can't be sure.

There's a page about Pulseaudio Volume Control http://http://freedesktop.org/softwa.../#installation here. That might help.

I do know that if you have Pulseaudio installed, Pulseaudio Volume Control is pretty much necessary to manage it. Not an expert myself, but that worked for me.

I waited for two days to be sure, and until now it looks fine.

As I've said, I can get the list of sound cards using alsa-info as root, but not as a regular user.
I used #strace aplay -l and searched for errors. I found access not permitted for some files in /dev/snd/. Since those files have the group "audio" and mod 660, I've added the regular user to audio group.