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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 ./ec2-data.nix ./amazon-grow-partition.nix ];
config = {
fileSystems."/" = {
device = "/dev/disk/by-label/nixos";
autoResize = true;
};
boot.initrd.kernelModules = [ "xen-blkfront" ];
boot.kernelModules = [ "xen-netfront" ];
boot.kernelParams = mkIf cfg.hvm [ "console=ttyS0" ];
# 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" ];
# Generate a GRUB menu. Amazon's pv-grub uses this to boot our kernel/initrd.
boot.loader.grub.version = if cfg.hvm then 2 else 1;
boot.loader.grub.device = if cfg.hvm then "/dev/xvda" else "nodev";
boot.loader.grub.timeout = 0;
boot.loader.grub.extraPerEntryConfig = mkIf (!cfg.hvm) "root (hd0)";
boot.initrd.postDeviceCommands =
''
# Force udev to exit to prevent random "Device or resource busy
# while trying to open /dev/xvda" errors from fsck.
udevadm control --exit || true
kill -9 -1
'';
# Mount all formatted ephemeral disks and activate all swap devices.
# We cannot do this with the ‘fileSystems’ and ‘swapDevices’ options
# because the set of devices is dependent on the instance type
# (e.g. "m1.large" has one ephemeral filesystem and one swap device,
# while "m1.large" has two ephemeral filesystems and no swap
# devices). Also, put /tmp and /var on /disk0, since it has a lot
# more space than the root device. Similarly, "move" /nix to /disk0
# by layering a unionfs-fuse mount on top of it so we have a lot more space for
# Nix operations.
boot.initrd.postMountCommands =
''
diskNr=0
diskForUnionfs=
for device in /dev/xvd[abcde]*; do
if [ "$device" = /dev/xvda -o "$device" = /dev/xvda1 ]; then continue; fi
fsType=$(blkid -o value -s TYPE "$device" || true)
if [ "$fsType" = swap ]; then
echo "activating swap device $device..."
swapon "$device" || true
elif [ "$fsType" = ext3 ]; then
mp="/disk$diskNr"
diskNr=$((diskNr + 1))
echo "mounting $device on $mp..."
if mountFS "$device" "$mp" "" ext3; then
if [ -z "$diskForUnionfs" ]; then diskForUnionfs="$mp"; fi
fi
else
echo "skipping unknown device type $device"
fi
done
if [ -n "$diskForUnionfs" ]; then
mkdir -m 755 -p $targetRoot/$diskForUnionfs/root
mkdir -m 1777 -p $targetRoot/$diskForUnionfs/root/tmp $targetRoot/tmp
mount --bind $targetRoot/$diskForUnionfs/root/tmp $targetRoot/tmp
if [ ! -e $targetRoot/.ebs ]; then
mkdir -m 755 -p $targetRoot/$diskForUnionfs/root/var $targetRoot/var
mount --bind $targetRoot/$diskForUnionfs/root/var $targetRoot/var
mkdir -p /unionfs-chroot/ro-nix
mount --rbind $targetRoot/nix /unionfs-chroot/ro-nix
mkdir -m 755 -p $targetRoot/$diskForUnionfs/root/nix
mkdir -p /unionfs-chroot/rw-nix
mount --rbind $targetRoot/$diskForUnionfs/root/nix /unionfs-chroot/rw-nix
unionfs -o allow_other,cow,nonempty,chroot=/unionfs-chroot,max_files=32768 /rw-nix=RW:/ro-nix=RO $targetRoot/nix
fi
fi
'';
boot.initrd.extraUtilsCommands =
''
# We need swapon in the initrd.
copy_bin_and_libs ${pkgs.utillinux}/sbin/swapon
'';
# Don't put old configurations in the GRUB menu. The user has no
# way to select them anyway.
boot.loader.grub.configurationLimit = 0;
# Allow root logins only using the SSH key that the user specified
# at instance creation time.
services.openssh.enable = true;
services.openssh.permitRootLogin = "without-password";
# Force getting the hostname from EC2.
networking.hostName = mkDefault "";
# Always include cryptsetup so that Charon can use it.
environment.systemPackages = [ pkgs.cryptsetup ];
boot.initrd.supportedFilesystems = [ "unionfs-fuse" ];
};
}
|