Fifth of Bootheaven - Dual Boot is for Tourists



Around 10 years ago I needed a laptop in a hurry. My tower was down and I had no time to build another, but I needed a computer for a couple of weeks. So I went to Walmart and bought an Acer laptop. (Shameless plug there. Everyone has a favorite brand, mine is Acer.) Eventually I did rebuild my tower and the laptop just never got a lot of use thereafter. It had a tiny (by today's standards) hard drive, not as much RAM as it might, and I just didn't have a lot of use for it.

In the days of coronavirus and the necessary imposed isolation, I came up with the idea of rebuilding the laptop entirely. For around $150 I added an extended battery pack, 2 GB of RAM and swapped out the 160 GB hard drive for 1 TB. So much for the hardware.



(A couple of years ago I used the laptop as a network client into my tower to do some extra number crunching, mostly accomplished with the lid shut, so yes the stickers are upside down if the lid is open, but right side up if the laptop is crunching numbers with the lid shut.)

Technical Notes

* Keen eyes will note above that I use GRUB Legacy not GRUB 2. The original installation was a Fedora Linux and Windows dual boot, booted with GRUB Legacy. Debian or Kali GRUB 2 installers saw Windows 7 (and each other), but not the Fedora installation. Further, in the process of modifying the MBR, they corrupted the Fedora partition.

* As I have said elsewhere, "If you love it, back it up. If it comes back to you, it's yours, if it doesn't it never was." After the first abortive attempt to use GRUB 2, I restored the Windows and Fedora configuration and resolved to stick with Grub Legacy as the path of least resistance. Like this...



* Note that the Kali installer saw Windows and Debian but not Fedora. In this case, it would not turn out to be enough to manually add Fedora later on, the installer corrupted the Fedora partition.

* Note that the installer identifies Windows as Vista. It's not. It's Windows 7 Professional, and it doesn't make a difference to GRUB other than the label.

* Special technical note about Windows 7 versus Windows 10. I have read enough accounts to believe that Windows 10 updates and patches have been known to suddenly and unexpectedly overwrite the MBR thus rendering dual boot computers unbootable. Consider the following: More and more functions are in the cloud these days. I can access G-Suite just as well with Debian as with Windows. Personally, I just kept Windows "in case" of a router or mobile phone flash or the odd piece of Windows only software. I would not consider an upgrade to an OS which I'll rarely use and may compromise my Bootheaven.

Now, having said not to overwrite the master boot record as above, Kali and Debian still need to be bootable like so:



* Kali and Debian have GRUB 2 bootloaders, but have not written the MBR. GRUB Legacy hands off to the respective /boot partitions.

So how does this work with multiple bootloaders handing off to one another?  First, none of these installations are virtual machines. Each of them is a native install. The disk setup looks like this:

Technical Notes

* You can only have four physical partitions on a hard drive. In this case, I needed the first three for the legacy Fedora, Fedora boot partition and Windows installations. The fourth became an extended partition. Debian and Kali are entirely installed in the extended partition.

* There is only one swap partition. Kali and Debian share it. I attempted to give them their own partition, but both installers were happy sharing a single swap partition.

* Note that if Kali and Debian were encrypted installs, sharing the swap partition would not work as swap space is also encrypted.

* Note that /dev/sda5 is encrypted. It is a shared storage partition for any boot that needs to use it.

* Note that only /dev/sda12 shows as a boot partition in the extended partition. The same is true of /root and /home. Regardless of how the Kali installer might have caused the Debian installation partitions to be flagged, going through the installation of both versions was similar in that I a) avoided overwriting the MBR and b) had both installers create a boot partition on /dev/sda.

* Note in the upper right corner /dev/sda and /dev/sdb are shown. /dev/sdb is 29.72 GB. It is a separate 32GB memory card which contains the Tails installation. If you have ever installed Tails, it is highly recommended by the developers that Tails not be installed on a hard disk for security. In keeping with this stricture, Tails is installed on a memory card in the SD slot and is now considered a permanent resident in the laptop. Since it's encrypted internally, casual theft of the card is not in itself a concern. Either GRUB Legacy or GRUB 2 can handle changing to a different default boot drive as needed.

I thought I'd share another item:



This is the schematic notes, warts and all. The reason I'm putting this up is to show two points which don't really conflict.

* Plan, but
* Be flexible

The first iteration was based on assumptions which turned out to be unworkable. And that's fine.

Proof of Concept (POC)

Last but not least, what would any technical write up be without proof of concept?

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