nixos-images/nix/kexec-installer/module.nix
2022-12-16 13:45:54 +01:00

136 lines
4.6 KiB
Nix

{ config, lib, modulesPath, pkgs, ... }:
let
restoreNetwork = pkgs.writers.writePython3 "restore-network" {
flakeIgnore = ["E501"];
} ./restore_routes.py;
# does not link with iptables enabled
iprouteStatic = pkgs.pkgsStatic.iproute2.override { iptables = null; };
in {
imports = [
(modulesPath + "/installer/netboot/netboot-minimal.nix")
];
# We are stateless, so just default to latest.
system.stateVersion = config.system.nixos.version;
# This is a variant of the upstream kexecScript that also allows embedding
# a ssh key.
system.build.kexecRun = pkgs.writeScript "kexec-run" ''
#!/usr/bin/env bash
set -ex
shopt -s nullglob
SCRIPT_DIR=$( cd -- "$( dirname -- "''${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
INITRD_TMP=$(TMPDIR=$SCRIPT_DIR mktemp -d)
cd "$INITRD_TMP"
pwd
mkdir -p initrd/ssh
pushd initrd
for key in /root/.ssh/authorized_keys /root/.ssh/authorized_keys2; do
if [ -e "$key" ]; then
# workaround for debian shenanigans
grep -o '\(ssh-[^ ]* .*\)' "$key" >> ssh/authorized_keys
fi
done
# Typically for NixOS
if [ -e /etc/ssh/authorized_keys.d/root ]; then
cat /etc/ssh/authorized_keys.d/root >> ssh/authorized_keys
fi
for p in /etc/ssh/ssh_host_*; do
cp -a "$p" ssh
done
# save the networking config for later use
if type -p ip &>/dev/null; then
"$SCRIPT_DIR/ip" --json addr > addrs.json
"$SCRIPT_DIR/ip" -4 --json route > routes-v4.json
"$SCRIPT_DIR/ip" -6 --json route > routes-v6.json
else
echo "Skip saving static network addresses because no iproute2 binary is available." 2>&1
echo "The image can depends only on DHCP to get network after reboot!" 2>&1
fi
find | cpio -o -H newc | gzip -9 > ../extra.gz
popd
cat extra.gz >> "''${SCRIPT_DIR}/initrd"
rm -r "$INITRD_TMP"
"$SCRIPT_DIR/kexec" --load "''${SCRIPT_DIR}/bzImage" \
--kexec-syscall-auto \
--initrd="''${SCRIPT_DIR}/initrd" \
--command-line "init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
# Disconnect our background kexec from the terminal
echo "machine will boot into nixos in in 6s..."
if [[ -e /dev/kmsg ]]; then
# this makes logging visible in `dmesg`, or the system consol or tools like journald
exec > /dev/kmsg 2>&1
else
exec > /dev/null 2>&1
fi
# We will kexec in background so we can cleanly finish the script before the hosts go down.
# This makes integration with tools like terraform easier.
nohup bash -c "sleep 6 && '$SCRIPT_DIR/kexec' -e" &
'';
system.build.kexecTarball = pkgs.runCommand "kexec-tarball" {} ''
mkdir kexec $out
cp "${config.system.build.netbootRamdisk}/initrd" kexec/initrd
cp "${config.system.build.kernel}/${config.system.boot.loader.kernelFile}" kexec/bzImage
cp "${config.system.build.kexecRun}" kexec/run
cp "${pkgs.pkgsStatic.kexec-tools}/bin/kexec" kexec/kexec
cp "${iprouteStatic}/bin/ip" kexec/ip
tar -czvf $out/nixos-kexec-installer-${pkgs.stdenv.hostPlatform.system}.tar.gz kexec
'';
# IPMI SOL console redirection stuff
boot.kernelParams = [
"console=ttyS0,115200n8"
"console=ttyAMA0,115200n8"
"console=tty0"
];
documentation.enable = false;
# Not really needed. Saves a few bytes and the only service we are running is sshd, which we want to be reachable.
networking.firewall.enable = false;
systemd.network.enable = true;
networking.dhcpcd.enable = false;
# for detection if we are on kexec
environment.etc.is_kexec.text = "true";
systemd.services.restoreNetwork = {
before = [ "network-pre.target" ];
wants = [ "network-pre.target" ];
wantedBy = [ "multi-user.target" ];
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
ExecStart = [
"${restoreNetwork} /root/network/addrs.json /root/network/routes-v4.json /root/network/routes-v6.json /etc/systemd/network"
];
};
unitConfig.ConditionPathExists = [
"/root/network/addrs.json"
"/root/network/routes-v4.json"
"/root/network/routes-v6.json"
];
};
# Restore ssh host and user keys if they are available.
# This avoids warnings of unknown ssh keys.
boot.initrd.postMountCommands = ''
mkdir -m 700 -p /mnt-root/root/.ssh
mkdir -m 755 -p /mnt-root/etc/ssh
mkdir -m 755 -p /mnt-root/root/network
if [[ -f ssh/authorized_keys ]]; then
install -m 400 ssh/authorized_keys /mnt-root/root/.ssh
fi
install -m 400 ssh/ssh_host_* /mnt-root/etc/ssh
cp *.json /mnt-root/root/network/
'';
}