Can I "restore" an iso image to my hdd to be bootable?
Why not use a bootable USB stick. On the arch-linux wiki there is a tutorial about how to create a bootable USB stick (live USB stick) for OS X:

Taken from the Arch Linux Wiki: https://wiki.archlinux.org/index.php/USB_Installation_Media

On Mac OS X

To be able to use dd on your usb device on a Mac you have to do some special maneuvers. First of all insert your usb device, OS X will automount it, and run

diskutil list


in Terminal.app. Figure out what your usb device is called - mine was called /dev/disk1. (Just use the mount command or sudo dmesg | tail.) Now you run

 diskutil unmountDisk /dev/disk1


to unmount the partitions on the device (i.e., /dev/disk1s1) while keeping the device proper (i.e., /dev/disk1). Now we can continue in accordance with the Linux instructions above (but use bs=8192 if you are using the OS X dd, the number comes from 1024*8).


  dd if=image.iso of=/dev/disk1 bs=8192
  20480+0 records in
  20480+0 records out
  167772160 bytes transferred in 220.016918 secs (762542 bytes/sec)


it is probably a good idea to eject your drive before physical removal at this point.

 diskutil eject /dev/disk1


Creating the bootable USB drive:
Overwrite the USB drive
Warning: This will irrevocably destroy all data on /dev/sdx.
Note: This method does not work with UEFI boot.
Note: Check with lsblk that the USB device is not mounted, and use /dev/sdx instead of /dev/sdx1. These are very common mistakes!

dd bs=4M if=/path/to/archlinux.iso of=/dev/sdx


Note: Some older firmware does not understand the isohybrid hack where start of fake partition offset is 0. See https://bugs.archlinux.org/task/32189 for a fix involving isohybrid.pl.

How to restore the USB drive
Because the ISO image is a hybrid which can either be burned to a disc or directly written to a USB drive, it doesn't include a standard partition table.
After you install Arch Linux and you're done with the USB drive, you should zero out its first 512 bytes (meaning the boot code from the MBR and the non-standard partition table) if you want to restore it to full capacity:

dd count=1 bs=512 if=/dev/zero of=/dev/sdx


Then create a new partition table (e.g. "msdos") and filesystem (e.g. EXT4, FAT32) using gparted, or from a terminal:
For EXT2/3/4 (adjust accordingly), it would be:

cfdisk /dev/sdx
mkfs.ext4 /dev/sdx1
e2label /dev/sdx1 USB_STICK


For FAT32, install the dosfstools package and run:

cfdisk /dev/sdx
mkfs.vfat -F32 /dev/sdx1
dosfslabel /dev/sdx1 USB_STICK


On the wiki there is some more information, for example if you would like to create a boot USB stick from a Windows environment.