[FreeNX-kNX] usb pen devices.

[Dimitar Paskov]

> Hi Dimitar and all,
> 
> Some time ago you mentioned you had resolved usb local devices on nx
> clients using LTSP technology.
> 
>> Devices like floppy, cd/dvdrom and usb sticks are working very well with thin clients due to the good work of the people at the LTSP project.
> 
> I was wondering how you did that. With ltspfs?
> 
> I'm really thinking about usb pen devices.
> What's the best way to mount these devices that are plugged in by the user?
> 
> Thanks.
> Chris.

Hi

(for short version go to the end)
Yes, you are right, I have local devices working in thin client 
environment. I use ltspfs with the help of udev and some shell 
scripting. I have made this under Ubuntu 6.06 with some additional 
scripts from LTSP distribution. The main programs are:

- ltspfsd - this is the daemon which is running on the thin client and 
is "watching" for local device status (there is a deb package for it)
- lbuscd - a perl daemon which communicates with the server on which is 
the running nx session (this is from the LTSP distro)
- some udev scripts
--------------
- lbussd - a perl daemon which runs on the server and communicates with 
lbuscd on the thin client (this is from the LTSP distro)
- lbus_event_handler.sh - a script that gets executed on the server upon 
event (like usb pen device insert/remove on the thin client) (this is 
from the LTSP distro)
- ltspfs - fuse based remote filesystem for ltsp thin cients (also has 
deb package)

How all this work. When there is an event (like adding a usb device) the 
udev daemon (with the help of the kernel) executes a script like this:
################
# USB Pens
KERNEL=="sd[a-z][1-4]",
RUN+="/etc/udev/scripts/ltsp-device.sh ${DEVNAME} ${ACTION}
#############
DEVNAME may be /dev/sda1 for example, ACTION is "add" or "remove"

This script sends information about the device to lbuscd daemon which 
forwards it to lbussd daemon running on the server. Then lbussd executes 
lbus_event_handler.sh which mounts the device with ltspfs command which 
communicates with ltspfsd daemon on the thin client. 
lbus_event_handler.sh also does some neat stuff like placing an icon on 
the users desktop pointing to the directory the device is mounted in. 
After the user has removed the device, this script removes the icon from 
his desktop and unmounts the device. (actually it is unmounted before 
that by the ltspfsd daemon). The best thing about ltspfs is that it 
unmounts devices automatically after short timeout and you can mount 
with sync option and be sure that all information will be copied before 
the device is unmounted. No more locked cdroms and broken usb 
filesystems. Floppies are mounted all the time (for obvious reasons), 
cd/dvds are mounted only when there is a medium in the device and usb 
stuff only when inserted. Note that there are 2 mounts that are 
happening. The fake one with ltspfs (based on fuse filesystem) that 
"mounts" the thin client from the server and the real mount of the 
device that happens on the thin client through ltspfsd. All this acts 
like the old supermount fs (in kernel 2.6.9 - 2.6.13) - the device gets 
mounted only when it is accessed.

May be I wrote too much :) anyway in short:
install ltspfsd on the thin client and copy lbuscd + udev scripts 
(/etc/udev/rules.d/15-ltsp-block.rules; 
/etc/udev/scripts/ltsp-device.sh) from the LTSP site. Install ltspfs on 
the server and copy lbussd and lbus_event_handler.sh from the LTSP site. 
Follow the scripts to see if all works like it should. Ask if you have 
any questions. Hope this helps :)