nixos-infect/README.md

This script aims to install NixOS on Digital Ocean droplets, Vultr servers, or
OVH Virtual Private Servers (starting from distros that these services support
out of the box).

## Source Distros

This script has been tested and can install NixOS from the following source distros:

On Digital Ocean:
- Fedora 24 x64
- Ubuntu 16.04 x64

On Vultr:
- Ubuntu 18.10 x64

On OVH Virtual Private Servers (experimental):
- Debian

On Hetzner cloud:
- Ubuntu 18.04

YMMV with any other hoster + image combination.

If you have a OpenVZ based virtualization solution then this, or any other OS takeover script will not work, this is fundamental to how OpenVZ works.

## Considerations

nixos-infect is so named because of the high likelihood of rendering a system
inoperable. Use with caution and preferably only on newly-provisioned
systems.

*WARNING NB*: This script wipes out the targeted host's root filesystem when it
runs to completion. Any errors halt execution. It's advised to run with
`bash -x` to help debug, as often a failed run leaves the system in an
inconsistent state, requiring a rebuild (in DigitalOcean panel: Droplet
Settings -> "Destroy" -> "Rebuild from original").

## Digital Ocean

*TO USE:*
- Add any custom config you want (see notes below)
- Deploy the droplet indicated at the top of the file, enable ipv6, add your ssh key
- `cat customConfig.optional nixos-infect | ssh root@targethost`

Alternatively, use the user data mechamism by supplying the lines between the following
cat and EOF in the Digital Ocean Web UI (or HTTP API):

```yaml
#cloud-config

runcmd:
  - curl https://raw.githubusercontent.com/elitak/nixos-infect/master/nixos-infect | PROVIDER=digitalocean NIX_CHANNEL=nixos-19.09 bash 2>&1 | tee /tmp/infect.log
```
Potential tweaks:
- `/etc/nixos/{,hardware-}configuration.nix`: rudimentary mostly static config
- `/etc/nixos/networking.nix`, networking settings determined at runtime tweak
  if no ipv6, different number of adapters, etc.

```yaml
#cloud-config
write_files:
- path: /etc/nixos/host.nix
  permissions: '0644'
  content: |
    {pkgs, ...}:
    {
      environment.systemPackages = with pkgs; [ vim ];
    }
runcmd:
  - curl https://raw.githubusercontent.com/elitak/nixos-infect/master/nixos-infect | PROVIDER=digitalocean NIXOS_IMPORT=./host.nix NIX_CHANNEL=nixos-19.09 bash 2>&1 | tee /tmp/infect.log

```

## Vultr

To set up a NixOS Vultr server, instantiate an Ubuntu box with the following "Startup Script":

```bash
#!/bin/sh

curl https://raw.githubusercontent.com/elitak/nixos-infect/master/nixos-infect | PROVIDER=vultr NIX_CHANNEL=nixos-19.09 bash
```

Allow for a few minutes over the usual Ubuntu deployment time for NixOS to download & install itself.

## Hetzner cloud

We need to replace our nameserver to point to the dedicated Hetzner DNS as opposed to `127.0.0.1:53` which is specific to Ubuntu.

```
sed -i "/nameserver/d" /etc/resolv.conf
echo "nameserver 213.133.98.98" >> /etc/resolv.conf
curl https://raw.githubusercontent.com/elitak/nixos-infect/master/nixos-infect | PROVIDER=digitalocean NIXOS_IMPORT=./host.nix NIX_CHANNEL=nixos-19.09 bash 2>&1 | tee /tmp/infect.log
```

## Motivation

Motivation for this script: nixos-assimilate should supplant this script
entirely, if it's ever completed. nixos-in-place was quite broken when I
tried it, and also took a pretty janky approach that was substantially more
complex than this (although it supported more platforms): it didn't install
to root (/nixos instead), left dregs of the old filesystem (almost always
unnecessary since starting from a fresh deployment), and most importantly,
simply didn't work for me! (old system was being because grub wasnt properly
reinstalled)