I messed up my system earlier, I was greeted with a black screen, when booting in to Ubuntu. When I started up my laptop, I selected the recovery option from the grub menu, and chose fallback at root terminal. I saw that I was able to use the add user command, with it, I probably could use to create a privileged user on my machine.
Isn't that a security issue?
One could have stolen my laptop and at startup chose recovery and add another user, I'm fudged then. Including my data.
Come to think of it, even if you somehow remove that entry, one could boot from a live-CD, get a
chroot up and running and then add another user, with the right privileges that allows it to see all my data.
If I set the BIOS to boot at my HD only, no USB, CD/DVD, Network startup, and set a BIOS password, it still wouldn't matter, because you'd still have that grub recovery startup entry.
I am fairly certain that someone from China, Russia can't hack my Ubuntu Trusty Tahr, from the network, because it's secure like that. But, if one has physical access to my – your – machine, then, well, that's why I'm asking this question. How can I secure my machine so that hacking through physical access is not possible?