Hello everybody.

This thread is not about how to make HP ScanJet 2400c working. It works fine after some searching on the net.

The only problem is as follows.after each system reboot I have to manually correct chmod for the /dev/bus/usb/xxx/xxx (corresponding to the scanner) to let the scanner work:
The solution of changing the permissions I've read in the tutorial found by Google.
I only dislike that I have to do this each time the PC was rebooted. And what's important - the device ID changes after reboot, so the solution of adding 'sudo chmod ...' somewhere to /etc/rc.d/rc.local will not work.
The PC is not mine, it's in another city, and each time the manager writes/calls me to help him (to do this), as he doesn't have admin (root) permissions.

Is there any solution to fix it for ever?

I think I must look to the groups. But I'm not sure.

Initial device permissions are generally handled by udev. You'll have to find the one that affects your scanner and modify it, or create a new one to override it.

http://www.reactivated.net/writing_udev_rules.html

It seems odd that the existing rules wouldn't at least have a "scanner" group or similar already set up for it though. The udev rules provided by the debian libsane package do. I suggest you check to see that everything is up-to-date installation-wise first.