SCSI CDRW Woes

bdemore · n00b Joined: 22 Oct 2002 Posts: 67

I think I've exhausted all the threads regarding this and am not sure where to turn. I'm trying to get a Yamaha SCSI CDRW to be recognized by Gnome Toaster which I emerged last night. My fstab looks like this:

/dev/cdroms/cdrom0 /mnt/cdrw auto noauto,ro,user 0 0

I can mount and read from it with no problem. When I issue the command cdrecord -scanbus I get the following:

Cdrecord 1.11a39 (i686-pc-linux-gnu) Copyright (C) 1995-2002 Jörg Schilling
cdrecord: Device or resource busy. Cannot open '/dev/sg0'. Cannot open SCSI driver.
cdrecord: For possible targets try 'cdrecord -scanbus'. Make sure you are root.
cdrecord: For possible transport specifiers try 'cdrecord dev=help'.

The command dmesg gives me:

Vendor: YAMAHA Model: CRW8424S Rev: 1.0j
Type: CD-ROM ANSI SCSI revision: 02
Attached scsi CD-ROM sr0 at scsi0, channel 0, id 5, lun 0
(scsi0:A:5): 20.000MB/s transfers (20.000MHz, offset 15)
sr0: scsi3-mmc drive: 24x/16x writer cd/rw xa/form2 cdda tray
Uniform CD-ROM driver Revision: 3.12

I have sg compiled into the kernel. I've read quite a bit about permissions but I don't think that's my problem. Any help would be appreciated.

BradN · Posted: Sat Nov 16, 2002 5:48 am Post subject:

have you tried it logged in as root?

bdemore · n00b Joined: 22 Oct 2002 Posts: 67

Yeah, same results

BradN · Posted: Sat Nov 16, 2002 7:54 am Post subject:

Hmm, I can't think of anything else offhand... I've only set up IDE CD burners through SCSI emulation. I don't know if there's anything else that must be done for real SCSI burners.

ronmon · Posted: Sat Nov 16, 2002 1:19 pm Post subject:

Maybe this will help. It's the relevant parts of my /etc/devfsd.conf:

This gives non-root users write permission

MBCook · Posted: Sat Nov 16, 2002 10:41 pm Post subject:

Do you have the CD mounted when you try to write to it? Also, are you sure it's sg0? Does sg0 even exist?
_________________
-- Michael

Read an intelligent book like "The New Thought Police" or "The War Against Boys", and learn the TRUTH.

bdemore · n00b Joined: 22 Oct 2002 Posts: 67

I don't even know what sg0 is. I thought maybe it refered to the SCSI generic module which i've got loaded.

MBCook · Posted: Sat Nov 16, 2002 11:58 pm Post subject:

Yes it does. Do you have one in /dev?

What the sgXs do is allow bypass any driver thats there (like the scsi-cdrom driver) and give a program total controll over the drive. This is needed for CD-R(W), tape drives?, scanners?, etc.
_________________
-- Michael

Read an intelligent book like "The New Thought Police" or "The War Against Boys", and learn the TRUTH.

bdemore · n00b Joined: 22 Oct 2002 Posts: 67

It's there but it's a 0 byte file. Maybe I need to change the permissions? Should my fstab reflect a /dev/sg0? I tried that but couldn't mount anything.

MBCook · Posted: Sun Nov 17, 2002 12:46 am Post subject:

It's fine that it's 0 bytes, there is nothing there. Is the drive mounted when you run cdrecord (or whatever)? Are you trying this with a CD in the drive? Sorry, but this is about as helpful as I can be. I've never used a CD writer under linux.
_________________
-- Michael

Read an intelligent book like "The New Thought Police" or "The War Against Boys", and learn the TRUTH.

bdemore · n00b Joined: 22 Oct 2002 Posts: 67

I have no problem mounting the drive as a cdrom but can't as a cdrw (I guess).

nalin · Posted: Sun Nov 17, 2002 1:59 am Post subject:

ronmon · Posted: Sun Nov 17, 2002 2:08 am Post subject:

For writing, the drive is identified by its SCSI address in the order of Channel, ID, Lun (0,6,0) in my case. You can see yours by doing 'cat /proc/scsi/scsi'.

That translates to /dev/scsi/host0/bus0/target6/lun0/generic in devfs parlance. If you take a close look at /dev/sg0 (sg2 in my case) you should find that it is a link to your device. I used a very explicit setup in my devfsd.conf example above that points directly to the device, assigned it permissions, and then linked it to a descriptive name (/dev/cdr) so I don't have to remember which sg* is which. I do the same for /dev/scanner and just the link for /dev/dvd.

I'm convinced that the solution to your problem lies in devfsd.conf. It took a while to get the hang of it, but once I did things just started working.

P.S. No, you don't mount it to write to it. In fact you can't because there is no file system yet.

bdemore · n00b Joined: 22 Oct 2002 Posts: 67

That's a lot of excellent descriptive help, thanks. Ronmon, could you post your fstab and devfs.config so that I can understand how they relate? Thanks again.

bdemore · n00b Joined: 22 Oct 2002 Posts: 67

OK, thanks to ronmon I think I've made a breakthrough. sg0 points to my SCSI tape drive and sg1 points to my cdrw. Now I just have to figure out how to tell the cd software to link my cdrw to sg1 instead of sg0. I know it is done in devfsd.conf but i still don't know which line to change with the modification.

ronmon · Posted: Sun Nov 17, 2002 12:13 pm Post subject:

Well, instead of cluttering up the thread with the entire files, how about the chunks that matter.

/etc/fstab (actually this does not matter because writing is done to the raw device)