I managed to follow the instructions in the documentation and install the provided dev root file system. That process creates the following partition scheme
1. p1 : /boot (16MB)
2. p2 : /rootfs (3GB)
3. p4 : extend (others)
4. p5 : swap (128MB)
5. p6 : /share (others)
They say the process is not reccomended, I didn't have much of a choice. For some reason Netcat didn't work for me to access the uboot settings. And at the moment I don't have a serial kit for it. I think if one would by this the Serial Kit would be a must.
1. After connecting up the hard drive
2. I copied over the files hddrootfs.tar.gz , ChangeMeDevHDD, ChangeMyUbootEnv, uImage.buffalo Kernel from the CD-ROM provided to smb://kuroip//mtd_device
3. Pressed the initsw button on the back till it beeped
some flashing, afterwards the above partition scheme was created and hddrootfs.tar.gz was untarred into /dev/sda2. I think you could replace hddrootfs.tar.gz with the tarball for arm9-genlink or arm9-Freelink and have a working system when you were done.
After a system reboot the flash was not accessible and the root file system was /dev/sda2
you have to change the location of the swap in /etc/fstab.
I don't know if 3GB is enough for a root file system, especially with gentoo. I ended up buying a USB/SATA bridge to connect to a workstation and use gparted to custom partition the drive