Change permissions on /dev file?

[Toralf Lund]

Toralf Lund wrote:

>
>>>>> How can I update permissions on a device file on an FC4 setup? I 
>>>>> mean, I know I can use chmod, of course, but the problem is that 
>>>>> for /dev special files, the changes are lost on reboot. [ ... ] 
>>>>
>>>>
>>>>
>>>>
>>>> grep -n "sg" /etc/udev/permissions.d/50-udev.permissions
>>>>  
>>>>
>>>> The permissions are set there.
>>>>  
>>>>
>>> Right. I haven't quite got used to this new(ish) udev stuff... Seems 
>>> to me now it must be the place for the setting I want, but the 
>>> location you mention can't be correct for my system, as /etc/udev 
>>> has no permissions.d.
>>>
>> Look to /etc/udev/rules.d
>> HTH
>
>
> I think I should be able to define an appropriate rule for my unit, 
> but I'm surprised to find that the udev doc does not mention a key 
> containing the device type or vendor/product id (as reported e.g. in 
> /proc/scsi/scsi.) Is there really now way to do direct match on those?


Actually, it may look like SYSFS{type} will give me what I want (for 
device type.) I now have added

KERNEL=="sg0", BUS=="scsi", SYSFS{type}=="6", SYMLINK="scanner", MODE="0666"

which quite definitely has an effect, but not the one I want. In fact 
after I did this, the device is still owned by root and accessible by 
nobody else (i.e. has mode 0600.) Then if a user logs in via a local 
GNOME session, owner is changed to that user, and the mode stays the 
same. This is the same kind of behaviour as for CD-ROM, but is not right 
in this case, as I want to share the scanner across the net (via saned 
or just startup of the scanner software via ssh.) In fact, I'm not happy 
with the general trend of assuming the desktop user "owns" everything, 
as to me, flexibility in sharing resources is a very large part of what 
Linux is or should be about.

Anyhow, how do I get udev to actually use the mode I've told it to use???

- Toralf