Let's see if somebody can answer this simple question. I have the latest stable openwrt running on an NSLU2.  I would like to mount a file system from a USB attached storage instead of /jffs. I cannot umount /jffs, however.

umount /jffs
umount: cannot umount /jffs: Device or resource busy

Even when I move /jffs with something like:
mount -o move /jffs /tmp/BLA

and mount a filesystem on /jffs, say with:

mount /dev/sda1 /jffs

when I install applications with opkg, data *still gets written to /tmp/BLA* where I moved /jffs!!!!!!!!!!!!!!!

Please help me with this, because this really renders the NSLU2 useless to me with openwrt, seeing as it does not permit installing any software on external storage!