usb is not available as normal user

[stefab]

Only launching qemu with sudo or as root i could manage usb devices. As usability issue there could be a workaround changing permission of usb devices (proc) in fstab or use some other workaround so normal user can manage usb devices in qemu.
See also this: http://fabrice.bellard.free.fr/qemu/qemu-doc.html#SEC28

[Peter Whittaker (pwwnow)]

From reading http://fabrice.bellard.free.fr/qemu/qemu-doc.html#TOC35, it appears that root privileges are required to do this, so qemu appears to be working properly. Marking as rejected.

Changing this would require non-trivial system changes, which require an accompanying specification. Please look into writing or working with others on such a spec.

Thanks!

[TJ (tj)]

I'm working with Gutsy and kvm/qemu. I got around this by modifying the permission rule in

/etc/udev/rules.d/40-permissions.rules

I added GROUP="plugdev" so that the USB devices are members of that group:

# USB devices (usbfs replacement)
SUBSYSTEM=="usb_device", MODE="0664", GROUP="plugdev"

Regular user accounts are usually members of that group, which means that qemu/kvm can be run as a regular user and access the USB devices:

$ sudo /etc/init.d/udev reload
$ sudo find /dev/bus/usb -exec ls -l {} \; | grep plugdev
crw-rw-r-- 1 root plugdev 189, 141 2007-10-31 18:58 014
crw-rw-r-- 1 root plugdev 189, 142 2007-10-31 18:58 015
crw-rw-r-- 1 root plugdev 189, 143 2007-10-31 19:29 016
crw-rw-r-- 1 root plugdev 189, 144 2007-10-31 19:34 017
crw-rw-r-- 1 root plugdev 189, 145 2007-10-31 18:58 018
crw-rw-r-- 1 root plugdev 189, 146 2007-10-31 18:58 019
crw-rw-r-- 1 root plugdev 189, 146 2007-10-31 18:58 /dev/bus/usb/002/019
crw-rw-r-- 1 root plugdev 189, 145 2007-10-31 18:58 /dev/bus/usb/002/018
crw-rw-r-- 1 root plugdev 189, 144 2007-10-31 19:34 /dev/bus/usb/002/017
crw-rw-r-- 1 root plugdev 189, 143 2007-10-31 19:29 /dev/bus/usb/002/016
crw-rw-r-- 1 root plugdev 189, 142 2007-10-31 18:58 /dev/bus/usb/002/015
crw-rw-r-- 1 root plugdev 189, 141 2007-10-31 18:58 /dev/bus/usb/002/014

A group could be created specifically for qemu/kvm but using plugdev makes more sense since it is there to provide support for hot-plugged devices.

[TJ (tj)]

I'm investigating options to allow qemu/kvm safe access to the USB devices.

The options seem to be (in increasing order of complexity:

1. Modify the udev rule as described here but as a general change to udev is not really a general solution for a pre-packaged solution.
2. Add a wrapper script to the qemu & kvm packages that adds the udev modification just whilst qemu/kvm is running, and removes it after.
3. Add a USB daemon to the qemu/kvm package that runs as root and communicates over dbus with the qemu/kvm user process.

[Daniel Gimpelevich (daniel-gimpelevich)]

This bug is not exclusive to qemu/kvm; it affects any software that deals with USB devices in userspace. I consider any USB /dev node not group-owned by plugdev to be a release-critical bug. You should put the following command into some kind of cron job:

ls -gR /dev/usb* /dev/bus/usb|grep -v ^d|grep -qv plugdev && echo Bug 60273 is not fixed!

[Dustin Kirkland  (kirkland)]

I've marked this bug (Bug #60273) a duplicate of Bug #156085, which has far more detail, and TJ has provided links to PPA packages of his which are trying to fix this problem.

:-Dustin

[Stephen Parry (sgparry)]

Eh? This bug (https://bugs.launchpad.net/bugs/60273<a href="https://bugs.launchpad.net/bugs/60273">https://bugs.launchpad.net/bugs/60273</a>) is about permissions in /dev/bus/usb the other (<a href="https://bugs.launchpad.net/bugs/156085">bug #156085</a>was about /proc/bus/usb/devices becoming obsolete. The bugs are largely unrelated. Please re-open!