12 Troubleshooting 12.6.3 Linux host CD/DVD drive not found (older distributions) On older Linux distributions, if your CD/DVD device has a different name, VirtualBox may be unable to find it. On older Linux hosts, VirtualBox performs the following steps to locate your CD/DVD drives: 1. VirtualBox examines if the environment variable VBOX_CDROM is defined (see below). If so, VirtualBox omits all the following checks. 2. VirtualBox tests if /dev/cdrom works. 3. In addition, VirtualBox checks if any CD/DVD drives are currently mounted by checking /etc/mtab. 4. In addition, VirtualBox checks if any of the entries in /etc/fstab point to CD/DVD devices. In other words, you can try to set VBOX_CDROM to contain a list of your CD/DVD devices, separated by colons, for example as follows: export VBOX_CDROM=’/dev/cdrom0:/dev/cdrom1’ On modern Linux distributions, VirtualBox uses the hardware abstraction layer (hal) to locate CD and DVD hardware. 12.6.4 Linux host floppy not found The previous instructions (for CD and DVD drives) apply accordingly to floppy disks, except that on older distributions VirtualBox tests for /dev/fd* devices by default, and this can be overridden with the VBOX_FLOPPY environment variable. 12.6.5 Strange guest IDE error messages when writing to CD/DVD If the experimental CD/DVD writer support is enabled with an incorrect VirtualBox, host or guest configuration, it is possible that any attempt to access the CD/DVD writer fails and simply results in guest kernel error messages (for Linux guests) or application error messages (for Windows guests). VirtualBox performs the usual consistency checks when a VM is powered up (in partic- ular it aborts with an error message if the device for the CD/DVD writer is not writable by the user starting the VM), but it cannot detect all misconfigurations. The necessary host and guest OS configuration is not specific for VirtualBox, but a few frequent problems are listed here which occurred in connection with VirtualBox. Special care must be taken to use the correct device. The configured host CD/DVD device file name (in most cases /dev/cdrom) must point to the device that allows writing to the CD/DVD unit. For CD/DVD writer units connected to a SCSI controller or to a IDE controller that inter- faces to the Linux SCSI subsystem (common for some SATA controllers), this must refer to the SCSI device node (e.g. /dev/scd0). Even for IDE CD/DVD writer units this must refer to the appropriate SCSI CD-ROM device node (e.g. /dev/scd0) if the ide-scsi kernel module is loaded. This module is required for CD/DVD writer support with all Linux 2.4 kernels and some early 2.6 kernels. Many Linux distributions load this module whenever a CD/DVD writer is detected in the system, even if the kernel would support CD/DVD writers without the module. VirtualBox supports the use of IDE device files (e.g. /dev/hdc), provided the kernel supports this and the ide-scsi module is not loaded. Similar rules (except that within the guest the CD/DVD writer is always an IDE device) apply to the guest configuration. Since this setup is very common, it is likely that the default configuration of the guest works as expected. 175