Just installed Ubuntu 9.10 from within windows XP and on the restart it starts to load but I get "No Root File system defined".
I tried to use Gpart but it wants to format my drive..any advise?

When you created the partitions, did you mark a file with / as active?
The forward slash denotes the root file system.
If you didn't mark a partition as active, you'll need to use a rescue disk to correct the problem.

@Mr-Bisquit

My understanding is Ubuntu was installed with wubi. Wubi creates file(s) on the MS Windows files system that holds Ubuntu's filesystem and swap space. So there would not be any additional partitions for Ubuntu.


@lunardragon

You might want to ask the moderators to move this thread to the Ubuntu forum. I think you are more likely to find somebody there who knows what's going on here. You can request it be move by clicking on the "Report" button in the lower right hand corner of each post (near "Edit" and/or "Quote").

And move it we did.......

I have no experience with installing from within Windows, but I would simply start over and do it the more conventional way:
Resize exisiting partitions to make space.
Boot up from the Ubuntu Cd and install.

Linux (GRUB to be precise) does not care if a partition is marked as active.

No, but the system does care. You can't boot a partition that won't load a kernel and the basic userland environment.
Wubi only creates an image to boot from, not file-systems or swap space. You're going to need an actually physical disk to manipulate the partitions properly and apply ntfs progs and what not to ensure the disk works as it should.Use wubi if you have at least space or the partitioning layout to create one extra primary and one extra extended logical partition. You can't share two different filing systems on the exact same space unless one is created in a virtual or contained environment.

If by "active" you mean the "bootable" flag is set, pixellany is correct. One of my computers doesn't have any partitions set as bootable. I just checked this one. It can boot to four different OSes, only one of which has the bootable flag set. Certainly GRUB does not require it. I don't *think* LILO does either. (Edit: I just verified that LILO -- at least as of v21.4.4 -- does not require the bootable flag to be set.) TMK, that flag is only used by Microsoft bootloaders and (possibly) back in the day by OS/2.

No. From the wubi FAQ:

Not being required to repartition the drive is one of the main attractions of wubi. That, and the fact that it installs like a MS Windows' application.

From an interview with Agostino Russo, one of the developers of wubi (I think -- I just skimmed the interview):