I was running Ubuntu Server on a mdadm RAID1 volume, and I ran into some problems so I decided to just do a clean install.
I booted with Gparted, stopped the mdadm array, and ran
--zero-superblock
on each partition, then deleted the partitions using Gparted.I then booted from an Ubuntu Server USB, configured the raid from scratch using the manual partitioning option, and installed Ubuntu 18.04.
First thing after installing the OS, I installed xfce4 and firefox along with a few other standard utilities and rebooted ran startx and fired up Firefox.
When logged I logged in, the tabs that I had open before reinstallation immediately opened up, I was still logged into SO. In fact, my entire home folder was still there.
I thought I had nuked everything and started fresh. I am totally mystified as to how this happened. Upon further inspection, I saw that all my files in my home folder were still there as well.
Is there some step that I missed? I thought the point of --zero-superblock and deleting the partitions was to get rid of any data on the drive. What did I miss? What does it take to do a guaranteed truly clean install? I am certain I have followed the same exact procedure before and my home directory did not persist.
Edit: So I zeroed out the component drives of the array, but now in the manual setup in the installer, I cannot set my new partition to "bootable" (nothing changes when I select it). Oddly, when creating the partitions it no longer asks me if I want to do a primary or a logical partition as it has in past times USING this same installer usb.