[CentOS] USB flash drive and VMs (Was Curmudgeoning)

David G. Miller dave at davenjudy.org
Fri Sep 5 14:59:29 UTC 2008


"Marcelo Roccasalva" <marcelo-centos at irrigacion.gov.ar> wrote:

> > Flash support under qemu seems to be about the same as CD-ROM support.  That
> > is, you can access a device present at start up but it's not swappable.
>   
>
> You can swap cdrom from qemu monitor. I haven't tried, but I think the
> same thing can be applied to usb..
It looks like the qemu monitor should let you either eject the device or 
delete/add the USB drive using usb_del and usb_add.  I wasn't able to 
get it to work.  W2K gives me a control to unmount the thumb drive in 
the system tray which makes the drive "disappear" from W2K.  
Unfortunately, attaching a new drive or just reattaching the old drive 
isn't recognized by W2K.  qemu monitor tells me it unable to add the new 
device or delete the old device.

If hot swapping a USB drive can be made to work with qemu, swapping a 
USB drive will still be ugly.  The USB device number assigned by the 
kernel changes each time I swap thumb drives.  This isn't too bad but 
access to /proc/bus/usb/<usb_bus_number>/<usb_dev_number> is root:root 
with permissions rw-r--r--.  This means that each time I swap the drive 
I have to chmod the "new" USB device entry.  I don't see this changing 
even if I can get qemu to let me add the new device.

I'll have to try using qemu monitor to swap a CD-ROM at some point in 
the future.  Usually I only use W2K and IE under qemu to access those 
few sites that still only work with IE (e.g., my state's income tax site).

Cheers,
Dave

-- 
Politics, n. Strife of interests masquerading as a contest of principles.
-- Ambrose Bierce



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