On Tue, Sep 27, 2005 at 11:04:18AM -0700, Bill Kendrick wrote: > I've got numerous USB-connected devices nowadays: > > * External hard drive enclosure > * Compact Flash memory card reader > * USB memory stick thumb pen flash drive key > * Sharp Zaurus cradle > * Digital Camera > * Stelladaptor (connect Atari joystick to PC) > > The top 3 are USB mass storage devices. Unfortunately, which "/dev/sdX" > device > they get appears to depend on how they're activated. If I plug in the USB > memory stick thing before turning on the HDD enclosure, it comes out as > /dev/sda. If I turn on the drive before plugging in the USB stick, it gets > /dev/sdb, instead. > > Briefly Googling around, I discovered something I hadn't heard of before, > called "udev". Apparently it allows devices to be assigned to specific > locations (somewhere in '/udev') based on the device's name. > (That way, icons on my desktop and/or mount points like /media/card0 and > /media/keychain0, would always point to the right place.) > > I installed it via 'aptitdue' but didn't have time to get it working, > and had to reboot at some point. I got a nice red warning message > during boot that 'udev' isn't supported with the older 2.6.x kernel I'm > using. > > Oh well. In the meantime, while I wait for Debian/etch to upgrade > (or if I decide to build my own kernel :^) ), is there a good HOWTO on > using udev that anyone can recommend? I remember someone here (Jeff?) > mentioning they use it. Is it working nicely for you? :)
I use it -- it works great. Debian's default is to mount it over /dev,
so that it does kind of what devfs used to do. In addition to the default rules
(which
create all of the usual device nodes) I have the following two
additional rules to name a couple of my devices:
KERNEL="sd?1",SYSFS{model}="ACEMAR ",SYSFS{vendor}="IDIGAT
L",SYMLINK="camera"
BUS="usb" SYSFS{product}="Palm Handheld*" KERNEL="ttyUSB*" SYMLINK="pilot"
MODE="666"
the second one I copied off the internet
the first one I wrote myself, taking advantage of udevinfo to tell me
some of the useful values.
To find information about the device that is currently connected to
/dev/hda1, do the following:
[EMAIL PROTECTED] ~]$ udevinfo -q path -n /dev/hda1
/block/hda/hda1
[EMAIL PROTECTED] ~]$ udevinfo -a -p /block/hda/hda1
Then you can take values from the output of udevinfo *from only one
level of the device chain* for the SYSFS{} attributes, and with
judicious use of KERNEL= you can choose which level of the device
chain to create the node or symlink for.
Note that jpilot doesn't take too kindly to the pilot symlink only
appearing when I hit the hotsync button, but it wouldn't take too
kindly to it even if the device node was always around. I resolved
this by switching to kpilot with korganizer and kaddressbook, which
are actually a whole lot nicer than jpilot.
--Ken Bloom
--
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