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nixpkgs/nixos/modules/virtualisation/amazon-init.nix

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Nix

{ config, pkgs, modulesPath, ... }:
# This attempts to pull a nix expression from this EC2 instance's user-data.
let
bootScript = pkgs.writeScript "bootscript.sh" ''
#!${pkgs.stdenv.shell} -eux
echo "attempting to fetch configuration from user-data..."
export PATH=${config.nix.package}/bin:${pkgs.wget}/bin:${pkgs.systemd}/bin:${pkgs.gnugrep}/bin:${pkgs.gnused}/bin:${config.system.build.nixos-rebuild}/bin:$PATH
export NIX_PATH=/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels
userData="$(mktemp)"
wget -q --wait=1 --tries=0 --retry-connrefused -O - http://169.254.169.254/2011-01-01/user-data > "$userData"
if [[ $? -eq 0 ]]; then
echo "user-data fetched"
# If the user-data looks like it could be a nix expression,
# copy it over. Also, look for a magic three-hash comment and set
# that as the channel.
if sed '/^\(#\|SSH_HOST_.*\)/d' < "$userData" | grep -q '\S'; then
channels="$(grep '^###' "$userData" | sed 's|###\s*||')"
printf "%s" "$channels" | while read channel; do
echo "writing channel: $channel"
done
if [[ -n "$channels" ]]; then
printf "%s" "$channels" > /root/.nix-channels
nix-channel --update
fi
echo "setting configuration"
cp "$userData" /etc/nixos/configuration.nix
else
echo "user-data does not appear to be a nix expression; ignoring"
fi
else
echo "failed to fetch user-data"
fi
type -f nixos-rebuild
nixos-rebuild switch
'';
in {
imports = [ "${modulesPath}/virtualisation/amazon-image.nix" ];
ec2.metadata = true;
boot.postBootCommands = ''
${bootScript} &
'';
}