I am afraid this could be a kind of bug:
Code:
cp /opt/content/books/id_rsa.pub /home/root/.ssh/authorized_keys
Meaning, that if the filesystem does not remove the previous file, we are wasting 4Kbytes of storage space each time we activate the dropbear. If it is so, one should remove that line after gaining access, or at least to use a conditional
if [ ! -e ... ];then instead. I'd suggest the former.