11 Troubleshooting
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.
11.5.6 VBoxSVC IPC issues
On Linux, VirtualBox makes use of a custom version of Mozilla XPCOM (cross plat-
form component object model) for inter- and intra-process communication (IPC). The
process VBoxSVC serves as a communication hub between different VirtualBox pro-
cesses and maintains the global configuration, i.e. the XML database. When starting
a VirtualBox component, the processes VBoxSVC and VirtualBoxXPCOMIPCD are
started automatically.They are only accessible from the user account they are running
under. VBoxSVCowns the VirtualBox configuration database which normally resides
in ˜
/.VirtualBox. While it is running, the configuration files are locked. Com-
munication between the various VirtualBox components and VBoxSVC is performed
through a local domain socket residing in /tmp/.vbox-<username>-ipc. In case
there are communication problems (i.e. a VirtualBox application cannot communicate
withVBoxSVC), terminate the daemons and remove the local domain socket directory.
11.5.7 USB not working
If USB is not working on your Linux host, make sure that the current user is a mem-
ber of the vboxusers group. On older hosts, you need to make sure that the user
has permission to access the USB filesystem (usbfs), which VirtualBox relies on to
retrieve valid information about your host’s USB devices. The rest of this section only
applies to those older systems.
Note: The current rdesktop-vrdp implementation does not support accessing
USB devices through the sysfs!
As usbfs is a virtual filesystem, a chmod on /proc/bus/usb has no effect. The
permissionsfor usbfs can therefore only be changed by editing the /etc/fstab file.
For example, most Linux distributions have a user group called usb or similar,of
which the current user must be a member. To give all users of that group access to
usbfs, make sure the following line is present:
# 85 is the USB group
none /proc/bus/usb usbfs devgid=85,devmode=664 0 0
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