Dual Boot dm-crypt'ed USB Drive?

LoneStar · 2014-12-02 00:48:19

I'm attempted to dual boot two Arch installs, each with dm-crypt/luks. I've been able to do this with a single Arch on a USB drive...but with both I'm hitting some snags (perhaps just in theory).

What I'm imagining:

          +----------------------------------+
/dev/sdb  | MBR                              |
          +----------------------------------+
/dev/sdb1 | /boot for Arch 1st (Unencrypted) |
          +----------------------------------+
/dev/sdb5 | Luks for Arch 1                  |
          | +------------------------------+ |
          | | / for Arch 1                 | |
          | |                              | |
          | |                              | |
          | +------------------------------+ |
          +----------------------------------+
/dev/sdb2 | /boot for Arch 2 (Unencrypted)   |
          +----------------------------------+
/dev/sdb6 | Luks for Arch 2                  | 
          | +------------------------------+ |
          | | / for Arch 2                 | |
          | |                              | |
          | |                              | |
          | +------------------------------+ |
          +----------------------------------+

Also, note they wouldn't be using the partition number, but /dev/mapper...etc but the physical partitioning would look like this.

Does this look doable, or has anyone set up something similar before? (i.e. before I spend hours installing and encrypting )

The part I'm not sure about is which Arch install "owns" the grub install? Or does it even matter/can they share the MBR? I.e. Only one of them installs grub to the MBR...the other simple exists with a /boot at some partition that the other Arch install hopefully finds?

Thanks for any help!

fsckd · 2014-12-02 04:08:35

I don't see why it shouldn't be doable. Only one Arch will "control" Grub. I think the other Arch can be detected for Grub. Even if it doesn't, it is not difficult to make an entry yourself. (If i was doing it, i wouldn't bother with autodetection at all.)

If I may ask, why two Arches?

Strike0 · 2014-12-02 11:49:19

I don't think grub will autodetect the second install, because it looks at the linux packages in /boot and only the /boot of the "controlling" install will be mounted. But making a manual entry for the second install is troublefree with Arch indeed, because the kernel is not versioned. What you could also do is only have one /boot partition and let the second install use different names for the kernel/initramfs than default. Yet that is arguably more fiddling than creating a second small boot partition.

LoneStar · 2014-12-04 01:57:58

Thanks for the replies, I'm going to try and get this working over the weekend once I have a few hours to spare! I'll report back here with my findings. After looking into it a bit deeper, I think it's possible as well. I may have originally been over thinking it, but time will tell!

As for the why; I'm trying to combine some resources (cause it all comes down to the dollar!) for a work project. We currently have two separate machines (both with VASTLY different setups, yet both running Arch) that I'm trying to combine into a single dual boot machine. I thought about virtualization, or using something like docker but these machines are mutually exclusive (i.e. they never need to be running at the same time) and are both very resource intensive. Both machines use full system encryption as a company policy, and it appears to me that using a dual boot setup would be the most resource efficient and safest bet in the long run.

Arch Linux

#1 2014-12-02 00:48:19

Dual Boot dm-crypt'ed USB Drive?

#2 2014-12-02 04:08:35

Re: Dual Boot dm-crypt'ed USB Drive?

#3 2014-12-02 11:49:19

Re: Dual Boot dm-crypt'ed USB Drive?

#4 2014-12-04 01:57:58

Re: Dual Boot dm-crypt'ed USB Drive?

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