Intro

Aufs is a layered filesystem. You could use it to make 4 disks look like 1 among other things. I used it to make the SD card on a SBC read only which protects it from corruption. Once implemented, I haven't had a corrupted card since.

Obviously nothing will persist to disk, but it wouldnt be hard to create another partition to persist too. I believe this would still protect the essential parts of the filesystem.

Aufs

Aufs can be acquired from git://git.code.sf.net/p/aufs/aufs3-linux

Clone that into the root of your Kernel source and follow the Aufs instructions. I have used the linux-3.x-rcN branch on 3.19 rc2 with no problems.

The magic

The following init script is to be executed by the kernel. This will write everything written to the rootfs to RAM. It's possible somebody could come up with a way of safely persisting this to the card, or maybe to a network fs. Either way, it makes the whole system stable.

Now you must pass the kernel a bootarg something like this:

setenv bootargs console=ttyS0,115200 console=tty0 consoleblank=0 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait ro noatime init=/sbin/router-init.sh

Improvements

I think maybe using a tmpfs with a set limit would allow for things like df to work correctly. If you have any others, please let me know!