Changing fs type should show the format option as checked since it will be formatted

Confirming this error in Ubuntu 10.10 as well, as it happened to me last night during reinstallation/moving from 10.04 to 10.10. This is a critical error to me and caused the loss of 150 gigs in my user home directories. Luckily there are (somewhat dated) backups.

This JUST happened to me w/ the 11.10 daily build (kubuntu 8.5.11) the drive simply contains a / , swap , and /home partitons in that order. disk is a MBR scheme. the swap and /home are logical partitons with the / being a primary partition. i chose to format the / partition,(was running 10.10 already). and when it finally booted i found my /home partition had also been formated . both / and /home were already ext4 partitions.

This happened to me too yesterday. I don't recall any warning messages just a greyed out format box. I did see it but I thought I will be asked before proceeding. Older versions of ubuntu installers always used to ask for confirmation. Where did that go?

I lost about 200GB irreplaceable data and NO BACKUP. I'm devastated...

BTW, you can recover some files from a formatted partition. See e.g. PhotoRec. There are also more powerful proprietary tools that can recover pretty much everything including directory structure. That said WHY?

I just did this on 12.04. I chose ext4 in the Edit partition dialog box. I noted that the format box was unchecked. I ticked OK. The format box was in the "Install" dialog was STILL unchecked. I hit "Install Now". The precise moment I pressed "Install Now" it added a tick in the "Format?". I quickly tried to stop the install, but by the time I had it had already been formatted.

As I understand Ubiquity has a two second delay before it adds the tick to the "Format?" column; this allows the user to check twice (i.e in both dialogs) that the format box hasn't been checked, and still have their partition formatted under them.