What does this mean for full disk encryption security if the encrypted partition never gets mounted? On the one hand, because the encrypted partition doesn’t get mounted, I wonder if that means my FDE is compromised and the PC’s drives are easier to access than they’re supposed to be (i.e. in effect, I don’t have true FDE). But on the other hand, my passphrase entry is still required before Ubuntu completes booting up. So, that makes me wonder if I’m still getting the full benefit of FDE in terms of the PC being extremely difficult to access without the passphrase.
Here's the strange story of what's happening:
I successfully set up FDE on Ubuntu 14 on a PC quite some time ago and it worked correctly. Then when I tried to upgrade to a newer Ubuntu distribution, things went wrong and I couldn’t get the PC to boot up at all. The Ubuntu grub appeared, but the PC did nothing after selecting Ubuntu. Also, I couldn’t do a successful reinstall.
I gave up on using the PC for some time, then I recently tried again to figure out how to boot it up. This time at the Ubuntu grub I played around with Advanced Options and was able to initiate a boot up.
Now comes the strange issue with the full disk encryption I initially set up. When I power on the PC, I don’t get the correct passphrase entry dialog box that I used to get when FDE was working normally. Instead, I get some miscellaneous scrolling white text on a black screen for several seconds, and then I get a prompt to “Enter Passphrase” at the end of a block of scrolled text.
Some of the text above the prompt to enter a passphrase:
running init-premount mounting file root system unlocking the disk (with name sda1_crypt) then comes the "Enter passphrase" prompt
When I enter my passphrase (still the correct one from when I initially set up FDE), then the scrolling text resumes. In a few moments it boots up to the Ubuntu desktop. On the desktop I’m correctly presented with a logon option for the same account I set up initially, and an option to select a guest account.
After Ubuntu is booted, when I run Gparted, I can see the encrypted partition is not mounted. The only mounted partitions are 2 boot drives.
Here's what GParted looks like: