I found a solution to this problem, recreating file "casper/initrd.gz" after updating script "/init".
This update consists to insert the following lines before line containing "maybe_break mount" :
modprobe -r libusual
sleep 3
modprobe usb-storage
sleep 5
The second line is mandatory to let "libusual' remove smoothly before loading "usb-storage".
Moreover, I successfully performed a non-regression test with a "slow" machine which was not concerned by this problem.
I found a solution to this problem, recreating file "casper/initrd.gz" after updating script "/init".
This update consists to insert the following lines before line containing "maybe_break mount" :
modprobe -r libusual
sleep 3
modprobe usb-storage
sleep 5
The second line is mandatory to let "libusual' remove smoothly before loading "usb-storage".
Moreover, I successfully performed a non-regression test with a "slow" machine which was not concerned by this problem.