Debian Squeeze/Wheezy on Ultra 2?

Hello,

I have a problem to load the installer once reaching "boot:". When I enter "install video=off console=ttyS0,9600n8" I have the error "Undefined video mode number: 314". I tried to remove the video=off, but same error occured.

When happening, it proposes me to display available mode. I tried the first one "0" and then the following error happened:

[    1.045676] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
[    1.049523] Pid: 1, comm: swapper Not tainted 3.9-1-486 #1 Debian 3.9.8-1
[    1.049523] Call Trace:
[    1.049523]  [<c12b1573>] ? panic+0x6c/0x152
[    1.049523]  [<c1429d17>] ? mount_block_root+0x1e8/0x20a
[    1.049523]  [<c1002930>] ? do_alignment_check+0x15/0x73
[    1.049523]  [<c1429d77>] ? mount_root+0x3e/0x52
[    1.049523]  [<c1429e99>] ? prepare_namespace+0x10e/0x13e
[    1.049523]  [<c1429a88>] ? kernel_init_freeable+0x160/0x168
[    1.049523]  [<c12ae520>] ? kernel_init+0x5/0xb0
[    1.049523]  [<c12b8abb>] ? ret_from_kernel_thread+0x1b/0x30
[    1.049523]  [<c12ae51b>] ? rest_init+0x4f/0x4f

I also tried: linux text console=ttyS0,9600,n8 but same error occured.

I have a ReadyNas ultra2, I prepared my debian installer USB key under MacOs by doing the following:
sudo gunzip -c boot.img.gz > /dev/disk2

Then I copied the iso file debian-7.1.0-i386-netinst.iso to the usb key.

Thanks for your help.