Chapter 5. Booting the Installation System 5.3.5. Blacklisting kernel modules 5.4. Troubleshooting the Installation Process 5.4.1. CD-ROM Reliability 5.4.1.1. Common issues Sometimes it may be necessary to blacklist a module to prevent it from being loaded automatically by the kernel and udev. One reason could be that a particular module causes problems with your hardware. The kernel also sometimes lists two different drivers for the same device. This can cause the device to not work correctly if the drivers conflict or if the wrong driver is loaded first. You can blacklist a module using the following syntax: module_name .blacklist=yes . This will cause the module to be blacklisted in /etc/modprobe.d/blacklist.local both during the in- stallation and for the installed system. Note that a module may still be loaded by the installation system itself. You can prevent that from happening by running the installation in expert mode and unselecting the module from the list of modules displayed during the hardware detection phases. Sometimes, especially with older CD-ROM drives, the installer may fail to boot from a CD-ROM. The installer may also — even after booting successfully from CD-ROM — fail to recognize the CD-ROM or return errors while reading from it during the installation. There are many different possible causes for these problems. We can only list some common issues and provide general suggestions on how to deal with them. The rest is up to you. There are two very simple things that you should try first. If this does not work, then try the suggestions in the subsections below. Most, but not all, suggestions discussed there are valid for both CD-ROM and DVD, but we’ll use the term CD-ROM for simplicity. If you cannot get the installation working from CD-ROM, try one of the other installation methods that are available. • Some older CD-ROM drives do not support reading from discs that were burned at high speeds using a modern CD writer. • Some very old CD-ROM drives do not work correctly if “direct memory access” (DMA) is enabled for them. • If the CD-ROM does not boot, check that it was inserted correctly and that it is not dirty. • If the installer fails to recognize a CD-ROM, try just running the option Detect and mount CD- ROM a second time. Some DMA related issues with very old CD-ROM drives are known to be resolved in this way. 40