David Arnold 3d324e7533 lib/devos: bake devos repo into live cd (#168 )

fix #167 

This worked for me to bootstrap another machine.

2021-03-16 19:50:38 +00:00

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Making and writing an installable iso for hosts/NixOS.nix is as simple as:

flk iso NixOS

dd bs=4M if=result/iso/*.iso of=/dev/$your_installation_device \
  status=progress oflag=sync

This works for any file matching hosts/*.nix excluding default.nix.

Remote access to the live installer

The iso live installer comes preconfigured with a network configuration which announces it's hostname via MulticastDNS as hostname.local, that is NixOS.local in the above example.

In the rare case that MulticastDNS is not availabe or turned off in your network, there is a static link-local IPv6 address configured to fe80::47(mnemonic from the letter's position in the english alphabet: n=14 i=9 x=24; 47 = n+i+x).

Provided that you have added your public key to the authorized keys of the nixos user:

{ ... }:
{
  users.users.nixos.openssh.authorizedKeys.keyFiles = [
    ../secrets/path/to/key.pub
  ];
}

You can then ssh into the live installer through one of the following options:

ssh nixos@NixOS.local

ssh nixos@fe80::47%eno1  # where eno1 is your network interface on which you are linked to the target

Note: the static link-local IPv6 address and MulticastDNS is only configured on the live installer. If you wish to enable MulticastDNS for your environment, you ought to configure that in a regular profile.

EUI-64 LLA & Host Identity

The iso's IPv6 Link Local Address (LLA) is configured with a static 64-bit Extended Unique Identifiers (EUI-64) that is derived from the host interface's Message Authentication Code (MAC) address.

After a little while (a few seconds), you can remotely disvover this unique and host specific address over NDP for example with:

ip -6 neigh show # also shows fe80::47

This LLA is stable for the host, unless you need to swap that particular network card. Under this reservation, though, you may use this EUI-64 to wire up a specific (cryptographic) host identity.

Bootstrap Target Machine

Note: nothing prevents you from remotely exceuting the boostrapping process.

Once your target host has booted into the live iso, you need to partion and format your disk according to the official manual.

Mount partitions

Then properly mount the formatted partitions at /mnt, so that you can install your system to those new partitions.

Mount nixos partition to /mnt and — for UEFI — boot partition to /mnt/boot:

$ mount /dev/disk/by-label/nixos /mnt
$ mkdir -p /mnt/boot && mount /dev/disk/by-label/boot /mnt/boot # UEFI only
$ swapon /dev/$your_swap_partition

Install

Install using the flk wrapper baked into the iso off of a copy of devos from the time the iso was built:

$ cd /iso/devos
$ nix develop
$ flk install NixOS --impure # use same host as above

Note: You could install another machine than the one your iso was built for, but the iso doesn't carry all the necesary build artifacts so the target would start to build the missing parts on demand instead of substituting them from the iso itself.

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