/usr/share/arduino/hardware/mighty-1284p/bootloaders/ is in arduino-mighty-1284p 0~svn20130430-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/Makefile
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/boot.h
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/optiboot.c
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/optiboot_atmega1284p.hex
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/optiboot_atmega1284p.lst
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/pin_defs.h
/usr/share/arduino/hardware/mighty-1284p/bootloaders/optiboot/stk500.h
/usr/share/arduino/hardware/mighty-1284p/bootloaders/standard/
/usr/share/arduino/hardware/mighty-1284p/bootloaders/standard/ATmegaBOOT.c
/usr/share/arduino/hardware/mighty-1284p/bootloaders/standard/ATmegaBOOT_1284P.hex
/usr/share/arduino/hardware/mighty-1284p/bootloaders/standard/ATmegaBOOT_1284P_8MHz.hex
/usr/share/arduino/hardware/mighty-1284p/bootloaders/standard/Makefile