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chsims1

Member

From: Holderness, UK

Registered: 2008-11-25

Posts: 83

[Solved] Problem with program access to USB device as normal user.

Hi,

I have a python program which accesses a USB device.  This works fine when run as 'su' but not as a normal user.  I can access USB sticks etc. ok as a normal user.

As a noob, this sounds to me like something connected with Udev rules, but I really have no idea exactly what I need to do to provide the access to the python program as a normal user.  Help please

Last edited by chsims1 (2009-01-22 11:31:08)

biagio

Member

From: Florence - Italy

Registered: 2008-02-29

Posts: 49

Re: [Solved] Problem with program access to USB device as normal user.

try to put your username instead of 0 in the line <policy user="0"> in the file /etc/dbus-1/system.d/hal.conf
and restart hal with:
sudo /etc/rc.d/hal restart

Last edited by biagio (2009-01-22 11:09:24)

chsims1

Member

From: Holderness, UK

Registered: 2008-11-25

Posts: 83

Re: [Solved] Problem with program access to USB device as normal user.

Ok Solved after some reading .....

1. Find where the device is mounted by running dmesg | tail before and after connecting it.
2. Find the vendor and product numbers by using udevadm on the above mount point.
3. Create a new udev rule in /etc/udev/rules.d named 85.usb.rules (use whatever you want as long as it ends in .rules):

SYSFS{idVendor}=="1941", SYSFS{idProduct}=="8021", MODE="0660",GROUP="usb"

4. Create a new group 'usb'
5. Add your normal user to that group.

I realise that the number at the beginning of the udev rule name determines the priority of the rule, but would someone like to suggest a "good" value?  It works fine as I have used it here, but I don't want to cause problems further down the line.

Wittfella

Member

From: Australia

Registered: 2008-05-27

Posts: 462

Re: [Solved] Problem with program access to USB device as normal user.

Glad that you found a solution, but I was going to ask if you had added your username to the 'storage' and/or 'disk' groups?

chsims1

Member

From: Holderness, UK

Registered: 2008-11-25

Posts: 83

Re: [Solved] Problem with program access to USB device as normal user.

Yes, I am a member of the storage group ... presumably otherwise I wouldn't have been able to write/read USB sticks.  I think the problem was that libusb can only be used by root.  Adding the rule allows group (usb) access too.