I couldn't find a concise post on how to load the Arduino bootloader onto an ATmega328p using the AVR Dragon under Linux. It took a bunch of failed attemps and lock-outs via fuses but here it is for Google to index and hopefully save someone a bunch of time:
sudo avrdude -v -e -c dragon_pp -P usb -p m328p -U flash:w:ATmegaBOOT_168_atmega328.hex -U lock:w:0xcf:m \
-U efuse:w:0xfd:m -U hfuse:w:0xda:m -U lfuse:w:0xff:m
I had to wire up the AVR Dragon for parallel mode as I was locked out of ISP programming after following incorrect instructions in a forum post. I suspect the above would work using ISP but haven't verified that (can't bring myself to detach all those wires!).