Synology NAS (DS412+) exploits

So, I've had my DS412+ for a while now, and have slowly been tweaking and playing with it.
I've turned it into an SSH gateway server, using several firewall rules, an extremely restrictive SSH config and a chroot jail to lock down any exposure to anything.

I used to use a TinyCoreLinux directory to chroot into and use cryptsetup (I can't be bothered to recompile all dependencies for the native NAS environment) so that I can mount an eSATA drive and rsync the data onto a backup drive... But I've found I also want to use NBD-server and attach a usb DVD-drive to the NAS so I can mount data disks and just generally use my NAS as a central block device location (why waste laptop power / usb ports / cables?) .

So, I said fairwell to TCL (the chroot environment I hacked together just wasn't stable enough) and said hello to Arch!
I was able to mostly follow the base steps from this page (https://wiki.archlinux.org/index.php/Installation_Guide#Install_the_base_system) - the exception being instead of a 'pacstrap /mnt base' I used 'pacman -r / -Sy base' since I was already in the chrooted environment I wanted to be in - and I have a setup where I get access to a great deal of Arch packages (going forward too as it's rolling release), minimal size, and fair support (I've always found their wiki's to be amazingly helpful).

Over the next few entries I'll post the raw commands in order to set up a basic Arch chroot install, how to build synology kernel modules, how to use the NBD (or how badly it works). I'll have to probably redo the kernel modules after a DSM update so I'll re-blog at that point too.