nixos-anywhere/nixos-remote

#!/usr/bin/env bash
set -eufo pipefail
set -x

showUsage() {
  cat <<USAGE
Usage: $0 [options] ssh-host

Options:

* -f, --flake flake
  set the flake to install the system from
* --arg name value
  pass value to nix-build. can be used to set disk-names for example
* --argstr name value
  pass value to nix-build as string
* --kexec url
  use another kexec tarball to bootstrap NixOS
USAGE
}

abort() {
  echo "aborted: $*" >&2
  exit 1
}

nix_args=()
kexec_url=https://github.com/nix-community/nixos-images/releases/download/nixos-22.05/nixos-kexec-installer-x86_64-linux.tar.gz

while [[ $# -gt 0 ]]; do
  case "$1" in
    -f | --flake)
      flake=$2
      shift
      ;;
    --argstr | --arg)
      nix_args+=("$1" "$2" "$3")
      shift
      shift
      ;;
    --help)
      showUsage
      exit 0
      ;;
    --kexec)
      kexec_url=$2
      shift
      ;;
    *)
      if [ -z ${ssh_connection+x} ]; then
        ssh_connection=$1
      else
        showUsage
        exit 1
      fi
      ;;
  esac
  shift
done

# ssh wrapper
timeout_ssh_() {
  timeout 10 ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no "$ssh_connection" "$@"
}
ssh_() {
  ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no "$ssh_connection" "$@"
}

# first check if the remote system is kexec booted
if $(ssh_ -- test -e /etc/is-kexec); then
  is_kexec=y
fi


echo ${is_kexec-n}
if [ ${is_kexec-n} != "y" ]; then
  # TODO we probably need an architecture detection here
  ssh_ << SSH
set -efux
os=\$(uname)
if [[ "\$os" != "Linux" ]]; then
  echo "This script requires Linux as the operating system, but got \${os}" >&2
  exit 1
fi
fetch(){
  if command -v curl >/dev/null 2>&1; then
    curl --fail -Ss -L "\$1"
  elif command -v wget >/dev/null 2>&1; then
    wget "\$1" -O-
  else
    echo "no downloader (curl or wget) found, bailing out"
    exit 1
  fi
}
if command -v tar >/dev/null 2>&1; then
  echo "no tar command found, but required to unpack kexec tarball" >&2
  exit 1
fi
rm -rf /root/kexec
mkdir -p /root/kexec
fetch "$kexec_url" | tar -C /root/kexec -xvzf-
export TMPDIR=/root/kexec
setsid /root/kexec/kexec/run
SSH
  # wait for machine to become unreachable
  while timeout_ssh_ -- exit 0; do sleep 1; done

  # watiting for machine to become available again
  until ssh_ -o ConnectTimeout=10 -- exit 0; do sleep 5; done
fi


ssh_ << SSH
set -efux
$(declare -p nix_args)
nix --extra-experimental-features nix-command --extra-experimental-features flakes \
  run github:nix-community/disko \
  --no-write-lock-file -- \
    --debug -m create "\${nix_args[@]}" --flake "$flake"

nix --extra-experimental-features nix-command --extra-experimental-features flakes \
  run github:nix-community/disko \
  --no-write-lock-file -- \
    --debug -m mount "\${nix_args[@]}" --flake "$flake"

nixos-install --flake "$flake"
reboot
SSH