Thanks, Clemens. Right, initially /dev/snd/*, /dev/dsp*, and /dev/audio* permissions were 600 root:root, and this is presumably set by udev. In this state, mpd2 could not access the devices, but if when I added mpd2 user to the root group it could, providing a somewhat insecure kludgey solution to my problem. So I keep looking for another solution... Then I added the following lines to my /etc/security/console.perms.d/50-default.perms: <sound>=/dev/dsp* /dev/snd/* /dev/audio* <console> 0666 <sound> 0600 root.audio and now the permissions are 0666 root.audio by default. When I log in as user tim, it appears that the permissions get changed to 0666 tim.audio. This should still be fine, bc my mpd2 user is in the audio group, so *should* have read/write access. When I su mpd2, the permissions listed are the same, but mpd2 can't access the devices. I haven't tried actually logging in as mpd2 bc I didn't think it would be any different. I will try that later, but this may all be a moot point bc mpd2 is basically going to be a "server-only" user, with SHELL=/sbin/nologin, so for all this, I've modified the user to use bash just for testing purposes. Interestingly, as mpd2, I get permission denied error when try to access /dev/snd/pcmC0D0c, but as tim I get the expected error: [mpd2@servy tim]$ ls -la /dev/snd total 0 drwxr-xr-x 2 root root 460 2008-02-06 22:17 . drwxr-xr-x 15 root root 4520 2008-02-06 22:17 .. crw-rw-rw-+ 1 tim audio 116, 17 2008-02-06 22:17 controlC0 crw-rw-rw-+ 1 tim audio 116, 22 2008-02-06 22:17 controlC1 crw-rw-rw-+ 1 tim audio 116, 12 2008-02-06 22:17 controlC2 crw-rw-rw- 1 tim audio 116, 4 2008-02-06 22:17 controlC3 crw-rw-rw-+ 1 tim audio 116, 13 2008-02-06 22:17 midiC0D0 crw-rw-rw-+ 1 tim audio 116, 18 2008-02-06 22:17 midiC1D0 crw-rw-rw- 1 tim audio 116, 3 2008-02-06 22:17 midiC3D0 crw-rw-rw-+ 1 tim audio 116, 16 2008-02-06 22:17 pcmC0D0c crw-rw-rw-+ 1 tim audio 116, 15 2008-02-06 22:17 pcmC0D0p crw-rw-rw-+ 1 tim audio 116, 14 2008-02-06 22:17 pcmC0D1p crw-rw-rw-+ 1 tim audio 116, 21 2008-02-06 22:17 pcmC1D0c crw-rw-rw-+ 1 tim audio 116, 20 2008-02-06 22:17 pcmC1D0p crw-rw-rw-+ 1 tim audio 116, 19 2008-02-06 22:17 pcmC1D1p crw-rw-rw-+ 1 tim audio 116, 11 2008-02-06 22:17 pcmC2D0c crw-rw-rw-+ 1 tim audio 116, 10 2008-02-06 22:17 pcmC2D0p crw-rw-rw-+ 1 tim audio 116, 9 2008-02-06 22:17 pcmC2D1c crw-rw-rw-+ 1 tim audio 116, 8 2008-02-06 22:17 pcmC2D2c crw-rw-rw-+ 1 tim audio 116, 7 2008-02-06 22:17 pcmC2D3c crw-rw-rw-+ 1 tim audio 116, 6 2008-02-06 22:17 pcmC2D4p crw-rw-rw-+ 1 tim audio 116, 5 2008-02-06 22:17 seq crw-rw-rw-+ 1 tim audio 116, 2 2008-02-06 22:17 timer [mpd2@servy tim]$ cat /dev/snd/pcmC0D0c cat: /dev/snd/pcmC0D0c: Permission denied [mpd2@servy tim]$ exit exit [tim@servy ~]$ cat /dev/snd/pcmC0D0c cat: /dev/snd/pcmC0D0c: File descriptor in bad state An interesting observation is that when the sound devices were owned by root:root, when I add mpd2 user to root group, mpd2 can access the sound devices. But when I change the sound device to be owned by root:audio, adding the mpd2 user to audio group doesn't allow mpd2 to access the devices! This tells me that there's more to this than the device permissions. Any ideas? Tim -----Original Message----- From: linux-audio-user-bounces@xxxxxxxxxxxxxxxxxxxx on behalf of Clemens Ladisch Sent: Thu 2/7/2008 12:18 AM Cc: linux-audio-user@xxxxxxxxxxxxxxxxxxxx Subject: Re: ALSA device not found by some users... why? Tim Black wrote: > User mpd2 needs access to ALSA devices bc I'm running MPD (music > player daemon) as this user. When this daemon tries to access ALSA > device hw:0,0, it gets an "Error opening ALSA device: hw:0,0 No such > device" error. (But if I run the daemon as 'tim' or root there are no > such errors.) When the device nodes in /dev/snd/ are created dynamically (with udev), it's possible that their permissions are set by the udev rules and do not come from the directory. When you log in as mpd2, what are the permissions of the files in /dev/snd/? Do you get the expected result when doing "cat /dev/snd/pcmC0D0c"? (The expected result is "file descriptor in bad state".) Regards, Clemens _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
