CD-ROM Troubleshooting

CD-ROM Troubleshooting

You need a CD-ROM drive that works under Linux to install Red Hat Linux from this book's companion CD-ROM. The initial Linux kernel comes with CD-ROM driver modules for all supported CD-ROM drives; therefore, you should not have any problem as long as Linux supports your CD-ROM. Remember that the CD-ROM drive's interface is what counts, not the brand name. For example, any CD-ROM drive with the IDE interface works under Linux, because Linux supports the IDE interface.

If Linux does not seem to recognize the CD-ROM drive after you reboot the system, try the following steps to fix the problem:

1. If Linux has not loaded the CD-ROM driver module, you can manually load the driver by logging in as root and typing the command modprobe cdrom. Then check if the CD-ROM drive works by typing eject /dev/cdrom-the CD-ROM drive door should open if it's working. You can then try to mount a CD-ROM.

2. If you have rebuilt the kernel with support for your CD-ROM drive, verify that you are indeed running the new kernel. To see the version number, type the uname -srv (or uname -a) command. This output from the uname command shows the kernel's version number, as well as the date on which the kernel was built. If that date does not match the date on which you rebuilt the kernel, you may not be running the new kernel. Go through the steps outlined in Chapter 21, and make sure you have really installed the new kernel. One common problem is forgetting to reboot, so try that as well.

3. Look at the contents of the /proc/devices file to verify that the CD-ROM device is present. Use the following procedure to view the contents of a /proc/devices file:

   cat /proc/devices | more
   Character devices:
     1 mem
     2 pty
     3 ttyp
     4 ttyS
     5 cua
     6 lp
     7 vcs
    10 misc
    13 input
   29 fb
    36 netlink
   ... lines deleted ...
   Block devices:
     1 ramdisk
     2 fd
     3 ide0
     9 md
    12 unnamed
    14 unnamed
    22 ide1
    38 unnamed
    39 unnamed

   This listing corresponds to the devices on one of my Red Hat Linux PCs. It shows two lists of devices-character devices, such as serial ports that transfer data one or more characters at a time, and block devices, such as hard disks that transfer data in fixed-size blocks. You should look for the CD-ROM device in the list of block devices. I know my CD-ROM drive is connected to the secondary IDE interface. The two IDE interfaces correspond to the devices ide0 and ide1 in /proc/devices. Because ide1 appears in the listing, I know that the CD-ROM driver is in the kernel.

   If you have a CD-ROM connected to a Sound Blaster Pro or compatible interface, look for a device number of 25 and the device name sbpcd.

   If you don't see a device that corresponds to your CD-ROM drive, you have not configured the kernel properly to include the CD-ROM driver. Reconfigure and rebuild the kernel, making sure that you include support for your CD-ROM drive.

   For some SCSI CD-ROM drives, you have to specify the SCSI adapter as a boot option before the Linux kernel can access the CD-ROM drive.

4. Verify that the CD-ROM driver detected the CD-ROM drive when the system started. Type the dmesg | more command to look at the boot messages and to see whether a line reports that the CD-ROM drive has been found. On my system, which has an ATAPI CD-ROM drive, the message looks like this:

   hdc: SAMSUNG CD-ROM SN-124, ATAPI CD/DVD-ROM drive

   If you find no boot message about the CD-ROM drive, make sure that the CD-ROM is physically installed. For an external CD-ROM drive, make sure that the drive is powered on and the cables are connected. Check any drive ID or jumpers, and make sure that they are set correctly. You may want to first make sure that the CD-ROM drive works under DOS; if you see the CD-ROM work under DOS, you can be sure that the drive is physically sound. Next, verify that you have rebuilt the kernel with support for the correct CD-ROM-drive interface.

5. Verify that you can read from the CD-ROM drive. Try the following command, and see whether the drive's activity light comes on (it should) and whether any error messages are present (they shouldn't be):

   dd bs=1024 count=5000 < /dev/cdrom > /dev/null
   5000+0 records in
   5000+0 records out
   

   The /dev/null device is what you might call the bit bucket. Output directed to /dev/null simply vanishes.

   If the dd command does not work, the device file for the CD-ROM device may not be set properly. Type the ls -l /dev/cdrom command to view detailed information about your CD-ROM device. The Red Hat Linux installation program sets up /dev/cdrom as a symbolic link to the actual CD-ROM device. For an ATAPI CD-ROM drive on the secondary IDE interface, for example, I look at the /dev/cdrom symbolic link to make sure that it points to the real CD-ROM device (/dev/hdc in this case), as follows:

   ls -l /dev/cdrom
   lrwxrwxrwx   1 root   root    3 Feb 17 13:49 /dev/cdrom -> hdc

6. Verify that you can mount the CD-ROM. Place a good CD-ROM (such as the CD-ROM from this book) in the CD-ROM drive, and try to mount it by using the following command:

   mount -t iso9660 -r /dev/cdrom /mnt/cdrom

   The -t iso9660 option specifies that the CD-ROM has an ISO-9660 file system, and the -r option says you want to mount the file system as read-only.

   If you can read from the CD-ROM drive with the dd command but cannot mount the CD-ROM, you may have configured the kernel without support for the ISO-9660 file system. To verify the currently supported file systems, use the following command:

   cat /proc/filesystems

   If you do not see iso9660 listed in the output, you have to rebuild the kernel and add support for the ISO-9660 file system.

7. If nothing works, you may want to read the latest CDROM-HOWTO document. To read the HOWTO documents, point your Web browser to http://www.ibiblio.org/pub/Linux/docs/HOWTO/CDROM-HOWTO (your Red Hat Linux system must be connected to the Internet for this to work).

   Cross Ref

   If you still cannot get the CD-ROM drive to work under Linux, you may want to post a news item to one of the comp.os.linux newsgroups. Chapter 16 describes how to post to newsgroups.

The following sections suggest solutions for a few more common problems.

Enhanced IDE/MFM/RLL disk/cdrom/tape/floppy support (CONFIG_BLK_DEV_IDE) [Y/m/n/?] y
   Include IDE/ATAPI CDROM support (CONFIG_BLK_DEV_IDECD) [Y/m/n/?] y

*
* SCSI support
*
SCSI support (CONFIG_SCSI) [Y/m/n/?] y
*
* SCSI support type (disk, tape, CD-ROM)
*
SCSI CD-ROM support (CONFIG_BLK_DEV_SR) [Y/m/n/?] y

Adaptec AHA1542 support (CONFIG_SCSI_AHA1542) [M/n/y/?] y

*
* Old CD-ROM drivers (not SCSI, not IDE)
*
Support non-SCSI/IDE/ATAPI CDROM drives (CONFIG_CD_NO_IDESCSI) [Y/n/?] y

ISO 9660 CDROM filesystem support (CONFIG_ISO9660_FS) [Y/m/n/?] y

sbpcd=0x230,SoundBlaster

append = "sbpcd=0x230,SoundBlaster"