docs/dualboot.md: init

docs/dualboot.md

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+# Dualbooting NixOS and FreeBSD
+
+Out of curiosity, I decided to dual-boot NixOS and FreeBSD on my laptop, sharing
+one disk. I document the process here for future reference:
+
+## Linux install
+
+First, flash a stick with NixOS, then boot into it, wipe your disk, create two
+partitions, one being boot, the other your main NixOS partition. Then, follow
+these commands:
+
+```bash
+sudo su
+
+cryptsetup luksFormat /dev/diskname/partition
+
+cryptsetup open /dev/diskname/partition crypt
+
+mkfs.btrfs -L nixos /dev/mapper/crypt
+
+mount /dev/mapper/crypt /mnt
+
+btrfs create subvolume /mnt/nix
+btrfs create subvolume /mnt/home
+btrfs create subvolume /mnt/persist
+
+mkdir /mnt/boot
+mount /dev/partition # boot partition
+```
+
+Then, copy [my nixos flake](https://github.com/bloxx12/nichts) to `/mnt`, you
+can remove it from there later on.
+
+```bash
+git clone https://github.com/bloxx12/nichts /mnt
+```
+
+In there, change the file system uuids to the correct ones, you can see them
+using
+
+```bash
+sudo blkid
+```
+
+Then, install NixOS itself:
+
+```bash
+nixos-install --impure --flake /mnt/nichts#<hostname> -j 1 --cores 2
+```
+
+Wait for that to finish, then reboot.
+
+If your system works, great! if not, redo from the beginning.
+
+After that, set up FreeBSD the following way: