Believe it or not, while your in Microsoft Windows you can actually start a virtual machine off of a bootable USB. I have tried in the past to figure out a way of doing this with the Virtual PC product, as well as off of Sun’s Virtual box, with no luck. When I am on the road with my work laptop, I only have MS Windows to hobble along with (this is a sorted diatribe for another day, but ultimately with update, after corporate update, anti-virus, drive encryption, firewall, etc., my old 486 is starting to look like IBM’s Roadrunner compared against this laptop. The only difference is my 486 had a toggle switch to go from 33 to 66 Mhz, lets see the Roadrunner do that. I am being very facetious). Nevertheless, when I was in Windows, I really couldn’t find a way to start Linux off of the USB, and I really didn’t want to have to create a separate Virtual Machine image for linux (partially because I have my bootable USB linux configured the way I like).
So recently I installed Linux Mint on my USB, and once again tried to glean any solution to solve this problem. In linux this is a non-issue, so I wanted to revisit this in MS Windows. After some digging I did find an interesting switch option in QEMU, that allows you to boot off of a Physical Drive.
Naturally in MS Windows devices mean something inherently different, but I was curious to see how Windows addressed my USB device. With A little research, I found that WMI, has a way to display the actual device names of the Hard drives. So using the Windows Management Instrumentation Command-line (WMIC), you can identify the device(s) in one line. Open the MS Windows command line (cmd.exe) and type:
wmic diskdrive list
You will see the actual device names, (not the dumbed down C:, D:). This is where you can actually find the device name of your USB thumb drive. In the output you should see two fields, DeviceID (or Name) and InterfaceType. If you can’t clearly identify them from the command line, just redirect the output to a text file (or from the commandline wmic diskdrive list > output.txt).
Make sure that the InterfaceType says USB, and just validate the device.
This is the part where I come in with the big fat scary:
WARNING: BE VERY VERY VERY CAREFUL WHEN YOU ATTEMPT TO ACCESS THE DEVICE DIRECTLY. I CAN NOT BE RESPONSIBLE FOR DAMAGES (IN GENERAL, BUT THIS CASE PARTICULARLY), YOU NEED TO UNDERSTAND WHAT YOU ARE DOING, BECAUSE YOU ABSOLUTELY DO NOT WANT TO HAVE QEMU BOOT FROM YOUR CURRENTLY ACTIVE HARD DRIVE.
SEE QEMU WARNING.
Now that we have that out of the way, and you have the device name in hand you can start QEMU from the command line like this:
qemu -L . -m 256 -std-vga -soundhw all -full-screen -kernel-kqemu
-usb -hda \\.\PHYSICALDRIVE1_example
Add any of your favorite command line parameters to QEMU as appropriate to your machine, just make sure you change the \\.\PHYSICALDRIVE1_example to your device name, and it should boot. One point to note, this will be slow, but it keeps you from having to store a separate image on your hard drive.
Last remaining issue, I am still unable to get the bootable USB to access the whole drive space (or even extend out the persistence to the Maximum size 2048, (limited by the FAT partition)).
I haven’t dissected the SquashFS to see if there is a way to get the /CDROM mounting to map as read/write. If anyone has figured this out, please let me know.
Supporting arguments:
Thanks again for reading,
- - tekgnu - -
tekgnu OpenSource Bootable USB, Linux, Linux Mint, Qemu, Thumbdrive, USB
