Kevin's musings

Poked around with
Linux Hotplug
both last night and some today. It doesn’t seem to be very easy to
debug and you would think that it could be setup by default to
handle many of the common things you would want to do with
it. For example, I wanted to have it so I could attach my new
camera via USB cable, press the USB button on the cradle and
have it copy all the pictures off it, optionally delete them,
and disconnect. By default hotplug will see the camera, load the
scsi disk driver and say that it’s /dev/sda1, and thats it.

In order to get it all working as I wanted, I had to setup 2
scripts. First of all I made a /etc/hotplug/usb/usb-storage
script. This script (which didn’t exist before I made it) is
called by the /etc/hotplug/usb.agent when a “usb storage” device
connects. The /etc/hotplug/usb/usb-storage script gets passed a
number of things in env variables. If the $ACTION variable is
“add” then the device is connecting. I have the script look for
that and then mount the camera on /mnt/camera and run the second
script. Also, and this took me a while to figure out, I had to
run a link from the file refered to in $REMOVER back to the
/etc/hotplug/usb/usb-storage script. $REMOVER is run when the
device disconnects. The usb-storage script then catches a
$ACTION of “remove” and umounts the /mnt/camera.

The second script is just a simple script that copies the files off
the camera device and runs a program called
jhead
which can manipulate the EXIF headers that most digital cameras put in
images. In this case I have jhead rewrite the filename of the
image to YYYYMMDDHHMMSS.jpg. Then the script deletes all the
files from the camera (since they have now been copied over to
the laptop drive).

Using this setup I have been able to have a pretty quick turnaround on
pictures, which is nice. Here’s some sample ones from yesterday
and today:
Yet more dog pictures.