I have a simple problem:

I can mount my usb-harddrive without problems.

I can copy files to it from KDE.

When i manually mount the drive and use the cp command to copy files to it (eg: /mnt/uba1 )
The copy stops after copying some files and then marks NO SPACE LEFT ON DRIVE.
It looks like the copy goes to ramdrive and gives error when it runs out of memory.
Is there some kind of option i have to add to the cp command so that i can automate copies via shellscript?
If i mount the drive from withing KDE the copy runs for a lot longer then when manually mounted, but in the end i get IO errors, which i don't get from within KDE.
Does anyone know what exact mountcommand is issued by KDE so that i can include it in my script?

Basically what i want to do is take a big directory and copy it via shellscript to a USB2 device.