[linux-audio-user] audio cdrom permissions

derek holzer linux-audio-user@music.columbia.edu
Mon May 19 17:09:00 2003


hi gang,

still tracking this problem, so let me reply to the two kind people that 
have written so far. to clarify, i am trying to RIP audio, not BURN it. 
it seems both folks started thinking about write permissions and not 
necessarily read permissions.

devdsp@mail2.inform.dk wrote:

>>The easiest way is to chmod all of these entries to 777. You need to be able to
>>write to your CD-ROM drive as a regular user, after all :)
>>    
>>

i have done this, and it makes no difference. also, being a member of 
group "cdrom" and "disk" doesn't make much diff, so i can't imagine that 
being in "cdromwriter", as you suggest elsewhere, would change this..... 
funny thing is that it ACTS like i haven't changed these permissions! as 
you can see below, when i try chmod 777, it doesn't affect it, even 
though i am 'su'... what am i doing wrong here?

debian:/home/derek# chmod 777 /dev/sg0
debian:/home/derek# ls -al /dev/sg0
lr-xr-xr-x    1 root     root           36 May 19 22:15 /dev/sg0 -> 
scsi/host0/bus0/target0/lun0/generic


Paul Perkins wrote:

>Under 2.4.x kernel (or earlier), burning CDs (and possibly ripping audio
>CDs too) needs access to the "generic scsi" device for the drive (don't
>you love those violent terms for copying data?). Conventionally called
>/dev/sg0, device (21,0). The "0" may be another number if you have
>multiple real or emulated SCSI devices. I'm not sure, but I think this
>may change in the 2.6 kernel series.
>

i do have a /dev/sr0
lr-xr-xr-x    1 root     root           36 May 19 22:15 /dev/sg0 -> 
scsi/host0/bus0/target0/lun0/generic

and the new permissions for its target are as follows:

debian:/# ls -al /dev/scsi/host1/bus0/target0/lun0/
total 0
drwxrwxrwx    1 root     root            0 Jan  1  1970 .
drwxr-xr-x    1 root     root            0 Jan  1  1970 ..
brwxrwxrwx    1 root     cdrom     11,   0 Jan  1  1970 cd
crwxrwxrwx    1 root     root      21,   1 Jan  1  1970 generic

once i changed the permissions sucessfully to those above, cdparanoia 
gives me this when i try to Query an audio CD:

--------------begin
debian:/home/derek# cdparanoia -vQ
cdparanoia III release 9.8 (March 23, 2001)
(C) 2001 Monty <monty@xiph.org> and Xiphophorus

Report bugs to paranoia@xiph.org
http://www.xiph.org/paranoia/

Checking /dev/cdrom for cdrom...
    Testing /dev/cdrom for cooked ioctl() interface
        /dev/scsi/host1/bus0/target0/lun0/cd is not a cooked ioctl CDROM.
    Testing /dev/cdrom for SCSI interface
        generic device: /dev/scsi/host1/bus0/target0/lun0/generic
        ioctl device: /dev/scsi/host1/bus0/target0/lun0/cd

Found an accessible SCSI CDROM drive.
Looking at revision of the SG interface in use...
    SG interface version 3.1.24; OK.

CDROM model sensed sensed: TOSHIBA DVD-ROM SD-C2502 1711


Checking for SCSI emulation...
    Drive is ATAPI (using SCSI host adaptor emulation)

Checking for MMC style command set...
    Drive is MMC style
004: Unable to read table of contents header

Unable to open disc.  Is there an audio CD in the drive?
-----------------end

so i am still not sure what the problem is....

>If some of the applications you are using are installed with set-uid,
>(perhaps on a helper program rather than the main one), that would
>explain why similar actions may only work as user root in one
>application, but work as a normal user in another application.
>

none of the apps were knowingly installed set-uid... they all came from 
deb packages, though, so i know of no way to tell for certain. how to 
find out? how to change?

it's stuff like this that makes me think my laptop is haunted ;-)

thanks for your suggestions,
derek

>On Sun, 2003-05-18 at 13:03, derek holzer wrote:
>  
>
>>> i've been having a bit of trouble with playing and ripping CDs, maybe 
>>> someone here can help?
>>> 
>>> i'm running Debian on a laptop, and as root i don't have any serious 
>>> problems doing either, but as a user it becomes a bit wierd... let me 
>>> explain...
>>> 
>>> as user, i am in groups cdrom and disk. i have set permissions as follows:
>>> 
>>> in /dev:
>>> lr-xr-xr-x    1 root     root           13 May 18 17:31 cdrom -> 
>>> cdroms/cdrom0
>>> drwxr-xr-x    1 root     root            0 Jan  1  1970 cdroms
>>> 
>>> in /dev/cdroms
>>> lr-xr-xr-x    1 root     root           34 Jan  1  1970 cdrom0 -> 
>>> ../scsi/host1/bus0/target0/lun0/cd
>>> 
>>> in /dev/scsi/host1/bus0/target0/lun0/
>>> brw-rw-rw-    1 root     cdrom     11,   0 Jan  1  1970 cd
>>> 
>>> i have none of these other cdrom devices listed in /dev:
>>> /dev/hdc
>>> /dev/sr0
>>> /dec/scd0
>>> but my drive appears to be ATAPI with SCSI emulation. i have added the 
>>> following to my /etc/lilo.conf to reflect this:
>>> append="hdc=ide-scsi"
>>> although commenting this out doesn't seem to do much.
>>> 
>>> i can rip CDs as a user with Grip, but RipperX tells me i need 
>>> permission to access the CD drive [cannot open cdrom drive]. i can play 
>>> CD audio with Alsaplayer, but not with XMMS.  likewise, xfreecd doesn't 
>>> find the drive, but workman does. very inconsistant! running cdparanoia 
>>> -vQ as user gives the following:
>>> 
>>> Checking /dev/cdrom for cdrom...
>>>     Testing /dev/cdrom for cooked ioctl() interface
>>>         /dev/scsi/host1/bus0/target0/lun0/cd is not a cooked ioctl CDROM.
>>>     Testing /dev/cdrom for SCSI interface
>>>         No generic SCSI device found to match CDROM device 
>>> /dev/scsi/host1/bus0/target0/lun0/cd
>>> 
>>> it seems that there are still some permissions to change somewhere, but 
>>> i can't for the life of me figure out where!
>>> 
>>> what have i missed?
>>> 
>>> thanks,
>>> derek
>>    
>>