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# Configuration for Amazon EC2 instances. (Note that this file is a
# misnomer - it should be "amazon-config.nix" or so, not
# "amazon-image.nix", since it's used not only to build images but
# also to reconfigure instances. However, we can't rename it because
# existing "configuration.nix" files on EC2 instances refer to it.)
{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.ec2;
in
{
imports = [
../profiles/headless.nix
# Note: While we do use the headless profile, we also explicitly
# turn on the serial console on ttyS0 below. This is because
# AWS does support accessing the serial console:
# https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configure-access-to-serial-console.html
./ec2-data.nix
./amazon-init.nix
];
config = {
assertions = [
{ assertion = versionOlder config.boot.kernelPackages.kernel.version "5.17";
message = "ENA driver fails to build with kernel >= 5.17";
}
];
boot.growPartition = true;
fileSystems."/" = mkIf (!cfg.zfs.enable) {
device = "/dev/disk/by-label/nixos";
fsType = "ext4";
autoResize = true;
};
fileSystems."/boot" = mkIf (cfg.efi || cfg.zfs.enable) {
# The ZFS image uses a partition labeled ESP whether or not we're
# booting with EFI.
device = "/dev/disk/by-label/ESP";
fsType = "vfat";
};
services.zfs.expandOnBoot = mkIf cfg.zfs.enable "all";
boot.zfs.devNodes = mkIf cfg.zfs.enable "/dev/";
boot.extraModulePackages = [
config.boot.kernelPackages.ena
];
boot.initrd.kernelModules = [ "xen-blkfront" ];
boot.initrd.availableKernelModules = [ "nvme" ];
boot.kernelParams = [ "console=ttyS0,115200n8" "random.trust_cpu=on" ];
# Prevent the nouveau kernel module from being loaded, as it
# interferes with the nvidia/nvidia-uvm modules needed for CUDA.
# Also blacklist xen_fbfront to prevent a 30 second delay during
# boot.
boot.blacklistedKernelModules = [ "nouveau" "xen_fbfront" ];
boot.loader.grub.device = if cfg.efi then "nodev" else "/dev/xvda";
boot.loader.grub.efiSupport = cfg.efi;
boot.loader.grub.efiInstallAsRemovable = cfg.efi;
boot.loader.timeout = 1;
boot.loader.grub.extraConfig = ''
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal_output console serial
terminal_input console serial
'';
systemd.services.fetch-ec2-metadata = {
wantedBy = [ "multi-user.target" ];
after = ["network-online.target"];
path = [ pkgs.curl ];
script = builtins.readFile ./ec2-metadata-fetcher.sh;
serviceConfig.Type = "oneshot";
serviceConfig.StandardOutput = "journal+console";
};
# Allow root logins only using the SSH key that the user specified
# at instance creation time.
services.openssh.enable = true;
services.openssh.permitRootLogin = "prohibit-password";
# Enable the serial console on ttyS0
systemd.services."serial-getty@ttyS0".enable = true;
# Creates symlinks for block device names.
services.udev.packages = [ pkgs.amazon-ec2-utils ];
# Force getting the hostname from EC2.
networking.hostName = mkDefault "";
# Always include cryptsetup so that Charon can use it.
environment.systemPackages = [ pkgs.cryptsetup ];
# EC2 has its own NTP server provided by the hypervisor
networking.timeServers = [ "169.254.169.123" ];
# udisks has become too bloated to have in a headless system
# (e.g. it depends on GTK).
services.udisks2.enable = false;
};
}
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