12 Troubleshooting 12.6.6 VBoxSVC IPC issues On Linux, VirtualBox makes use of a custom version of Mozilla XPCOM (cross platform com- ponent object model) for inter- and intra-process communication (IPC). The process VBoxSVC serves as a communication hub between different VirtualBox processes 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. VBoxSVC owns the VirtualBox configuration database which normally resides in ˜ /.VirtualBox. While it is running, the configuration files are locked. Communication between the various VirtualBox components and VBoxSVC is performed through a local domain socket residing in /tmp/.vbox-username-ipc. In case there are communica- tion problems (i.e. a VirtualBox application cannot communicate with VBoxSVC), terminate the daemons and remove the local domain socket directory. 12.6.7 USB not working If USB is not working on your Linux host, make sure that the current user is a member 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. As usbfs is a virtual filesystem, a chmod on /proc/bus/usb has no effect. The permissions for 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 Replace 85 with the group ID that matches your system (search /etc/group for “usb” or similar). Alternatively, if you don’t mind the security hole, give all users access to USB by changing “664” to “666”. The various distributions are very creative from which script the usbfs filesystem is mounted. Sometimes the command is hidden in unexpected places. For SuSE 10.0 the mount command is part of the udev configuration file /etc/udev/rules.d/50-udev.rules. As this distribution has no user group called usb, you may e.g. use the vboxusers group which was created by the VirtualBox installer. Since group numbers are allocated dynamically, the following example uses 85 as a placeholder. Modify the line containing (a linebreak has been inserted to improve readability) DEVPATH="/module/usbcore", ACTION=="add", RUN+="/bin/mount -t usbfs usbfs /proc/bus/usb" and add the necessary options (make sure that everything is in a single line): DEVPATH="/module/usbcore", ACTION=="add", RUN+="/bin/mount -t usbfs usbfs /proc/bus/usb -o devgid=85,devmode=664" Debian Etch has the mount command in /etc/init.d/mountkernfs.sh. Since that distribu- tion has no group usb, it is also the easiest solution to allow all members of the group vboxusers to access the USB subsystem. Modify the line domount usbfs usbdevfs /proc/bus/usb -onoexec,nosuid,nodev so that it contains domount usbfs usbdevfs /proc/bus/usb -onoexec,nosuid,nodev,devgid=85,devmode=664 As usual, replace the 85 with the actual group number which should get access to USB devices. Other distributions do similar operations in scripts stored in the /etc/init.d directory. 176