Can't format unallocated portion of HD?

[kilaueabart]

It looks like I have made myself a bit of trouble. I recently bought a new 500 Gb hard drive (SSD) and partitioned and formatted half of it to use for Ubuntu 12.04, saving half unallocated for later in case I would be able to add another Linux (e.g. Ubuntu MATE).

Now GParted seems to be telling me that I can't use the unallocated half of sdb unless I "use Partition menu options, such as unmount or swapoff, to deactivate all partitions on this device before creating a new partition table." And I can't do that with an active partition.

Does this mean I have to kill my installation of 12.04 before I can do anything else with the disk? I'm guessing the only way to do this is to go back to the Ubuntu LT install disk and use its GParted to reformat and partition the whole HD, but that idea hurts. I've got a lot of hours invested in /dev/sdb1.

[broadblues]

The problem is most likely that you can't repartition the disk while it is mounted and you can't unmount it whilst booted from it.

I suspect you can boot from the instal disk and add a partition in rescue mode, no need to trash the existing partition.

[kilaueabart]

Yes, thanks. I realized that as I awoke this morning, and have now set up the second half of the drive from the 12.04 install dvd. I tried to respond to this from there, but I can't remember my Hyperion forums password! So back to the installed version.

I was hoping beyond hope that maybe the downloaded-to-flash-drive MATE 15.10 installer failed to find any disks (at step 20, time zone) was because it was looking for a valid empty partition, although all my other installations have been quite willing to overwrite any partition whatsoever. Sure enough, installation step Detect Disks still fails. I sort of wonder whether it might just not recognize SSDs, but still it should at least find my OS4 disk.