Dual boot 2 Linux OSes with full disk encryption and dedicated shared storage

MrLinuxUser12 · 10-23-2018, 09:54 AM

Hello!

I am going to reinstall Linux on my notebook, and I've decided I want to go for a dual boot -- Debian and Parrot Security (another Debian derivative). Both of these have installers that allow for full disk encryption.

I've already set up a system with "manual" disk encryption before, utilizing the graphical installers, so I've got at least some knowledge in the field. I've never worked with the underlying commands concerning GRUB or CryptSetup, though.

My goal is to create a system with full disk encryption in legacy BIOS (to harness the advantage of TRUE full disk encryption), allowing dual boot of the two systems and (ideally) a shared storage space. Most likely a shared home partition.

The whole disk should be decryptable with just one password. And preferrably, I shouldn't have to enter the same password again just to unlock the shared storage space.

Now as I'm a relative beginner in this field, I wanted to ask the experts (you) on what's the best way to set this up (saving myself some hours of time over doing something that turns out to be wrong in hindsight).
Is there a clean and easy way to do this? If I need to get my hands dirty with commands, at what point are they absolutely required and what do I do?

RickDeckard · 10-23-2018, 01:30 PM

I'll suggest to you installing a shared boot partition for both Debian and Parrot Security to a USB drive which would remove the need for jumping through GRUB cryptodisk hoops while allowing your main hard drive to remain fully encrypted. Bonus of course being that whoever does not have your USB cannot access your device. You shouldn't need to do much of anything to get that set up, just select the USB as your boot partition and off you go.

And as for the shared storage, I would set it up from the command line prior to installing either system. Before the system install procedures, go to the terminal in both LiveCD's (I assume that is going to be your installation method) and unlock the finished product. Then start install and once you get to custom partitioning your home LV should be visible.

Oh, and when you're given this installation option to mount a filesystem elect to keep the shared filesystems as they are each time without formatting.

cantab · 11-03-2018, 05:33 PM

For the shared partition, you can add a keyfile to LUKS for the device, save a copy of the keyfile in each distro's root partition, and configure crypttab accordingly.

Here's an example crypttab from my Debian system where I was doing a similar thing. On that setup I was using LUKS on LVM, rather than the installer default of LVM on LUKS.

Code:

spelvia--ssd-root_crypt UUID=94f1724f-71bb-4a05-9805-5c7f81936bd3 none luks
spelvia--ssd-swap_crypt /dev/mapper/spelvia--ssd-swap /dev/urandom swap
spelvia--hdd-home_crypt /dev/mapper/spelvia--hdd-home /etc/luks/spelvia--hdd-home

zeebra · 11-05-2018, 05:03 AM

Sharing /home between 2 distroes is not a problem, as long as you take some precautions. You can use different usernames or place the user home directory on a different place.

For sharing you can make a sharepoint on the /home directory or you can give users rights to each others files or folders.