Just wanted to make a note that I'm running Linux Mint 18.1 (Mate desktop) in VirtualBox with xTIMEcomposer 14.3.0 and I was able to get the xTAG drivers working by simply running the provided driver install script. My Google searches only turned up results like the "Enable USB drivers on Linux" article, which is old. The solution listed there by XMOS does probably work for xTAG 2 devices, however, all of the new xTAG devices from XMOS are not shown in that tutorial, but are included in the new distrobution of xTIMEcomposer. For that reason, and the fact that it's probably just a better idea to use the tools that come with your software distrobution, I performed the following steps to enable support for my xTAG 3 device under Linux Mint in a virtual machine.
First, with the USB device connected to the physical computer and checking the box in VirtualBox's USB settings to use this xTAG device inside the VM, I ran:
$ sudo ~/XMOS/xTIMEcomposer/Community_14.3.0/scripts/check_xmos_devices.sh
... to make sure the script could "see" the attached USB xTAG 3. Then I ran...
$ sudo ~/XMOS/xTIMEcomposer/Community_14.3.0/scripts/setup_xmos_devices.sh
... to enable USB support with this device. Then I checked the output of xrun with the following commands:
$ cd ~/XMOS/xTIMEcomposer/Community_14.3.0; source ./SetEnv; cd -; $ xrun -l
And all is well. Hope maybe this helps somebody who finds this.