Here is some more information: As mentioned I am using Extlinux4.0.5
Here is one of the boot menu entries in extlinux.conf:
I have a boot partition named boot on which the kernel and initrd reside, I just copied the files from the Ubuntu (ext3) partition.
MENU INDENT 1
MENU LABEL ^Ubuntu Oneiric Ocelot 11.10
APPEND root=label=Ubuntu ro quiet splash
Both partitions reside on the same physical harddrive while Ubuntu is a logical partition inside an extended partition (the boot is a primary partition with the boot flag set).
The error message is:
on a different linux version with kernel 126.96.36.199 (based on Ubuntu) I get a bit further, after it seems to be running for a while it comes with the following error message:
Kernel panic - not syncing: VFS: Unable to mount root fs on unkown block(0,0)
Pid: 1, comm: swapper Not tainted 3.0.0-14-generic #23-Ubuntu
[<c151a3f2>] ? printk+0x2d/0x2f
[<c1136b2c>] ? sys_mknod+0x2c/0x30
[<c1127ce5>] ? sys_access+0x25/0x30
[<c17bf769>] ? start_kernel+0x358/0x358
followed by a call trace very similar to the previous one.
VFS: Cannot open root device "label=BT5" or unknown-block(0,0)
Please append a correct "root=" boot option; here are the available partitions:
Kernel panic - not syncing: VFS: Unable to mount root fs on unkown-block(0,0)
usb 4-2.2: new full speed USB device number 3 using ohci_hcd
Pid: 1, comm: swapper Not tainted 188.8.131.52 #1
I also tried to use root with the UUID but that didn't change anything.
About the usb line... I do have a USB device connected but I am not booting off of it.