Gnome broke my CD-ROM and audio...

Elric of Grans · 03-10-2006, 11:58 PM

G'Day,

I run Debian Sarge, and tried to install a new dockapp today. It required something from Gnome, so I did a simple apt-get install gnome... and somehow, that has broken my CD-ROM and audio.

With the CD-ROM first, this one has me really stumped: the draw now stays out! I can make it go back in by pressing the button, and if mounts a CD then it stays shut, but if I leave it empty and press the button to close it, the light with flash a little (checking if there is a CD in there), then it opens up again! I cannot come up with any good ideas for this one.

As for the audio, it is clearly permissions. If I try to run alsamixer, I get the old `Premission Denied' error, but what I am unable to access I cannot work out. My user account is a part of the audio group, and to make sure I made /dev/dsp, mixer, etc a+rw, but still get Permission Denied. If I sudo alsamixer, obviously no problems, and I get audio as expected, but I cannot work out what it is I am not able to access. Does Gnome perhaps set up some sort of a stupid new device node or something?

*sigh* I really wish I had not bothered with that dockapp now: I wasted 270MB and my afternoon and I do not even use Gnome. Any advice would be greatly appeciated, as I am getting pretty frustrated here.

stress_junkie · 03-11-2006, 06:21 PM

This is what I do with obscure permission problems. Open a terminal window and run the program with the strace utility.

$ strace alsamixergui

That will show a permission violation somewhere near the end of the output. Strace doesn't always explain the problem well. You may have to do some thinking and some ls-l <filename> to figure out what strace is showing you. Even so, it is handy for diagnosing problems like this.

Here is an example of a normal user trying to ls the /root directory.

Code:

$ strace ls /root
execve("/bin/ls", ["ls", "/root"], [/* 69 vars */]) = 0
uname({sys="Linux", node="mycomputer", ...}) = 0
brk(0)                                  = 0x805b000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/usr/X11R6/lib/tls/i686/librt.so.1", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/usr/X11R6/lib/tls/i686", 0xbfffe840) = -1 ENOENT (No such file or directory)
open("/usr/X11R6/lib/tls/librt.so.1", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/usr/X11R6/lib/tls", 0xbfffe840) = -1 ENOENT (No such file or directory)open("/usr/X11R6/lib/i686/librt.so.1", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/usr/X11R6/lib/i686", 0xbfffe840) = -1 ENOENT (No such file or directory)
open("/usr/X11R6/lib/librt.so.1", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/usr/X11R6/lib", {st_mode=S_IFDIR|0755, st_size=6144, ...}) = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=118281, ...}) = 0
old_mmap(NULL, 118281, PROT_READ, MAP_PRIVATE, 3, 0) = 0x40018000
...
... < cut out lots of stuff>
...
_llseek(3, 671, [671], SEEK_SET)        = 0
munmap(0x4028d000, 671)                 = 0
close(3)                                = 0
open("/root", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = -1 EACCES (Permission denied)
write(2, "ls: ", 4ls: )                     = 4
write(2, "/root", 5/root)                    = 5
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, ": Permission denied", 19: Permission denied)     = 19
write(2, "\n", 1
)                       = 1
exit_group(1)                           = ?

You can see at the beginning that a lot of files are called but they don't exist (ENOENT). That isn't what causes the ls command to fail. Near the end we start getting some permission denied messages. The only one of consequence is this one.

Code:

open("/root", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = -1 EACCES (Permission denied)

You can see that this line shows that I tried to open the /root directory and that permission was denied. So that gives you an idea of what an strace output will show you and what to ignore. All of those ENOENT - No such file or directory errors can be ignored. That's not always true about missing files; they just aren't causing a problem in this particular case.

I'll look around my Gnome configuration to see if I can figure out the cdrom behavior.

Elric of Grans · 03-12-2006, 03:54 PM

That seems like a really useful program: I can definitely make use of that in future! Thanks for that

My audio is now working (along with a few other odd permission things that I seem to have lost).