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{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.virtualisation.amazon-init;
script = ''
#!${pkgs.runtimeShell} -eu
echo "attempting to fetch configuration from EC2 user data..."
export HOME=/root
export PATH=${pkgs.lib.makeBinPath [ config.nix.package pkgs.systemd pkgs.gnugrep pkgs.git pkgs.gnutar pkgs.gzip pkgs.gnused pkgs.xz config.system.build.nixos-rebuild]}:$PATH
export NIX_PATH=nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels
userData=/etc/ec2-metadata/user-data
# Check if user-data looks like a shell script and execute it with the
# runtime shell if it does. Otherwise treat it as a nixos configuration
# expression
if IFS= LC_ALL=C read -rN2 shebang < $userData && [ "$shebang" = '#!' ]; then
# NB: we cannot chmod the $userData file, this is why we execute it via
# `pkgs.runtimeShell`. This means we have only limited support for shell
# scripts compatible with the `pkgs.runtimeShell`.
exec ${pkgs.runtimeShell} $userData
fi
if [ -s "$userData" ]; then
# 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*||')"
while IFS= read -r channel; do
echo "writing channel: $channel"
done < <(printf "%s\n" "$channels")
if [[ -n "$channels" ]]; then
printf "%s" "$channels" > /root/.nix-channels
nix-channel --update
fi
echo "setting configuration from EC2 user data"
cp "$userData" /etc/nixos/configuration.nix
else
echo "user data does not appear to be a Nix expression; ignoring"
exit
fi
else
echo "no user data is available"
exit
fi
nixos-rebuild switch
'';
in {
options.virtualisation.amazon-init = {
enable = mkOption {
default = true;
type = types.bool;
description = ''
Enable or disable the amazon-init service.
'';
};
};
config = mkIf cfg.enable {
systemd.services.amazon-init = {
inherit script;
description = "Reconfigure the system from EC2 userdata on startup";
wantedBy = [ "multi-user.target" ];
after = [ "multi-user.target" ];
requires = [ "network-online.target" ];
restartIfChanged = false;
unitConfig.X-StopOnRemoval = false;
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
};
};
};
}
|