ok,

here's what i did. Took an external hdd plugged it in, ran fdisk on it, thought i'd set the disk it to be the whole disk with a linux label. Then thought and written the partition table.
I then ran mk2fs. I've moved a load of data onto it and today I happened to run fdisk -l which showed:

Disk /dev/sda: 2000.4 GB, 2000406183936 bytes
255 heads, 63 sectors/track, 243202 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sda doesn't contain a valid partition table

It appears that i didn't set the partition up correctly. Either i didn't write the partition table to disk or didn't setup the partition properly for some other reason.

mke2fs did create a filesystem on the disk and the data is showing and available. Do i need to worry? can i remedy without losing the data. Is it possible to set up a file system without a partitioned disk?

Thanks

I don't think it's possible to write on a disk that has no partitions. However, I'm sure you can write to the MBR without making any partitions, but that's for something else.

Either way it seems that you haven't created a partition since fdisk returned invalid partition table. So you need to create a partition. Use fdisk to create a partition. Either you make the whole hard disk, like all 2,000 gigs one partition are a small fraction of that. If you want something that's a bit easier to make a partition, use partition editor or qtparted. I like partition editor better. You can use these programs by booting a LiveCD like Knoppix. You can download the cd image from their website and burn the image to a cd-r, then boot it from there.

You can create a filesystem with no partition table. Most flash drives come formatted this way, with a FAT filesystem occupying the whole space. Your filesystem should be fine, and your data should not be at risk.

ok, great, thanks guys, so it's fine as it is.