Question about CD-ROM device

dwhitney67 · 09-28-2007, 11:51 AM

In the past when I dealt with Linux Kernel 2.4.27, my CD-ROM drive was handled via /dev/scd0 and /dev/cdrom (was somehow created) to point to that character device. During boot-up from a CD-R, the root (within the grub configuration) was set to /dev/scd0. Everything worked fine.

Now that I am using Linux Kernel 2.6.20.1, my CD-ROM drive is recognized by Grub as /dev/hdb. Yet once I boot up, /dev/cdrom is pointing to /dev/scd0.

I suspect that /dev/scd0 is the correct device, however I am not sure if I have configured the kernel properly? The hardware I am using is the same. I have an IDE HDD and a CD-ROM drive connected to the same IDE cable. I am not a hardware guru, so all I can say is that the CD-ROM drive is a Plextor CD-R/W drive.

Btw, when I finish with the operations I perform after booting from the CD-ROM, I get a Kernel Panic... perhaps eluding that I am using the wrong device??

Here is the listing of my Grub menu.lst file that actually allows me to boot:

PHP Code:



# 
# Grub boot file 
# For iso9660 cdrom 
# 
# THIS IS NOT THE FILE YOU ARE LOOKING TO EDIT.  See /boot/boot/grub/menu.lst 
# (Unless, of course, you are tweaking the CD ROM boot sequence -- not likely.) 
# 
 
default 0 
timeout 10 
 
#splashimage=/boot/splash.xpm.gz 
 
title install 
root (cd) 
kernel /boot/vmlinuz-2.6.20.1 root=/dev/hdb init=/to_install/do_install_wrapper

Please, I need help with this issue. If there is any information that I have left out that could help troubleshoot this problem, please let me know.

Thank you.

GrapefruiTgirl · 09-28-2007, 01:29 PM

I'm not sure I totally understand what the CD-ROM booting situation is all about, but I will offer two ideas anyhow;

1 - As the CD-ROM device is identified by GRUB (and I presume by the system itself) as /dev/hdb I recommend deleting the symlink /dev/cdrom and recreating it to point to /dev/hdb. Just navigate to the /dev folder, and as root, delete the /dev/cdrom device node, and use

Code:

ln -s /dev/hdb /dev/cdrom

and

2 - perhaps for whatever reason, either your computer, or that particular CD drive, you may try adding hdb=ide-scsi on the kernel boot line. I suggest this, because under your old configuration, the CD drive was linked to a scsi device node, and it worked, so it may work again by doing this.

Let us know if this gets you anywhere

jailbait · 09-28-2007, 01:42 PM

In the 2.4 kernel IDE CDs were handled by emulating them as SCSI CDs. In the 2.6 kernel IDE CDs are handled as native IDE mode. The old SCSI emulation should be dropped.

In moving from the 2.4 kernel to the 2.6 kernel you should get rid of anything specifying IDE-SCSI emulation. You can straighten out /dev/cdrom with these commands:
rm /dev/cdrom
ln -s /dev/hdb /dev/cdrom

"Here is the listing of my Grub menu.lst file that actually allows me to boot:"

This implies that you have tried several menu.lst files. This one seems OK. If you have any menu.lst files where you
have passed hdb=ide-scsi as a kernel parameter then remove hdb=ide-scsi. The hdb=ide-scsi was used in the 2.4 kernel to specify IDE-SCSI emulation.

------------------
Steve Stites

GrapefruiTgirl · 09-28-2007, 02:03 PM

Quote:

Originally Posted by jailbait

In the 2.4 kernel IDE CDs were handled by emulating them as SCSI CDs. In the 2.6 kernel IDE CDs are handled as native IDE mode. The old SCSI emulation should be dropped.
Steve Stites

Humm, so maybe CONTRARY to my suggestion, it may actually be the source of the issue, rather than a solution? If there were the IDE-SCSI flag in use, it may actually cause the problem?

If so-- fancy that! I learn something EVERY DAY around here! Thanks.

dwhitney67 · 09-28-2007, 02:27 PM

Jailbait and GrapefruiTGirl -

In the past when I dealt with 2.4.27, there was nothing special about the menu.lst file that specified to treat the CD-ROM device (/dev/scd0) as an ide-scsi. The same with the new menu.lst.

I have found that the "eject" command accepts the device name as a parameter. I suppose I could be specific when using this command to eject /dev/hdb, instead of relying on it to use whatever /dev/cdrom points to.

When I am booting from the CD-ROM and running Busybox, I am operating in read-only mode (except for /tmp and /var/log which are setup as read/write ram-disks). Thus changing the /dev/cdrom link (if any) would not be possible.

Anyhow, I have another pressing matter (for which I have sought help)... my keyboard isn't working after boot-up. Thus it is impossible right now to analyze the system after it has booted into a shell.

Anyhow, thanks for your help. I was hoping that there was a kernel configuration option that I should enable or disable, but perhaps the issue with the CD-ROM drive is not "really" an issue, and all that is needed is to adjust the link of /dev/cdrom.