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• Check that your BIOS actually supports booting from CD-ROM (only an issue for very old systems) and that CD booting is enabled in the BIOS.
• If you downloaded an iso image, check that the md5sum of that image matches the one listed for the image in the MD5SUMS file that should be present in the same location as where you downloaded the image from.
$ md5sum debian-testing-i386-netinst.iso
a20391b12f7ff22ef705cee4059c6b92 debian-testing-i386-netinst.iso
Next, check that the md5sum of the burned CD-ROM matches as well. The following command should work. It uses the size of the image to read the correct number of bytes from the CD-ROM.
$ dd if=/dev/cdrom | \
> head -c ‘stat --format=%s debian-testing-i386-netinst.iso‘ | \
> md5sum a20391b12f7ff22ef705cee4059c6b92 - 262668+0 records in
262668+0 records out
134486016 bytes (134 MB) copied, 97.474 seconds, 1.4 MB/s
If, after the installer has been booted successfully, the CD-ROM is not detected, sometimes simply trying again may solve the problem. If you have more than one CD-ROM drive, try changing the CD-ROM to the other drive. If that does not work or if the CD-ROM is recognized but there are errors when reading from it, try the suggestions listed below. Some basic knowledge of Linux is required for this. To execute any of the commands, you should first switch to the second virtual console (VT2) and activate the shell there.
• Switch to VT4 or view the contents of /var/log/syslog (use nano as editor) to check for any specific error messages. After that, also check the output of dmesg.
• Check in the output of dmesg if your CD-ROM drive was recognized. You should see something like (the lines do not necessarily have to be consecutive):
Probing IDE interface ide1...
hdc: TOSHIBA DVD-ROM SD-R6112, ATAPI CD/DVD-ROM drive
ide1 at 0x170-0x177,0x376 on irq 15
hdc: ATAPI 24X DVD-ROM DVD-R CD-R/RW drive, 2048kB Cache, UDMA(33)
Uniform CD-ROM driver Revision: 3.20
If you don’t see something like that, chances are the controller your CD-ROM is connected to was not recognized or may be not supported at all. If you know what driver is needed for the controller, you can try loading it manually using modprobe.
• Check that there is a device node for your CD-ROM drive under /dev/. In the example above, this would be /dev/hdc. There should also be a /dev/cdrom.
• Use the mount command to check if the CD-ROM is already mounted; if not, try mounting it manually:
$ mount /dev/hdc /cdrom
Check if there are any error messages after that command.
• Check if DMA is currently enabled:
$ cd /proc/ide/hdc
$ grep using_dma settings
using_dma 1 0 1 rw
A “1” in the first column after using_dma means it is enabled. If it is, try disabling it:
$ echo -n "using_dma:0" >settings
Make sure that you are in the directory for the device that corresponds to your CD-ROM drive.
• If there are any problems during the installation, try checking the integrity of the CD-ROM using the option near the bottom of the installer’s main menu. This option can also be used as a general test if the CD-ROM can be read reliably.