first commit

Author: Mic92

Makefile

@@ -0,0 +1,11 @@
+INSTALL ?= install
+NIXOS_SHELL ?= $(shell nix-build --no-out-link default.nix)
+
+all:
+
+test:
+	QEMU_NET_OPTS="hostfwd=tcp::2222-:22" QEMU_OPTS="--smp 2 -m 1024" $(NIXOS_SHELL)/bin/nixos-shell example-vm.nix
+
+install:
+	$(INSTALL) -D bin/nixos-shell $(DESTDIR)$(PREFIX)/bin/nixos-shell
+	$(INSTALL) -D share/nixos-shell/nixos-shell.nix $(DESTDIR)$(PREFIX)/share/nixos-shell/nixos-shell.nix

README.md

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+# nixos-shell
+
+* Spawns a headless vm based on a `vm.nix` file in the current directory.
+* Mounts `$HOME` and the user's nix profile into the container
+* No ugly qemu SDL window, no serial console with incorrect terminal dimension.
+* If a tmux session is available, the console is will be spawned in a new tmux pane, 
+  while the qemu interface will be started in the current active pane
+
+Example `vm.nix`:
+
+```nix
+{ pkgs, ...}: {
+  boot.kernelPackages = pkgs.linuxPackages_latest;
+}
+```
+
+## USAGE
+
+Start a vm:
+
+```console
+$ nixos-shell
+```
+
+or
+
+```console
+$ nixos-shell some-nix-module.nix
+```
+
+Quit the vm:
+
+```console
+$vm> poweroff
+```
+
+or in the qemu console:
+
+```console
+quit
+```
+
+Forward a port:
+
+```console
+$ QEMU_NET_OPTS="hostfwd=tcp::2222-:22" nixos-shell
+```
+
+More RAM:
+
+```
+$ QEMU_OPTS="-m 1024" nixos-shell
+```
+
+More CPUs:
+
+```
+$ QEMU_OPTS="--smp 2" nixos-shell
+```

bin/nixos-shell

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+#!/usr/bin/env bash
+
+set -euo pipefail
+
+script_dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+export QEMU_KERNEL_PARAMS="console=ttyS0 ${QEMU_KERNEL_PARAMS:-}"
+export QEMU_PATH=${PATH:-}
+if [[ -z "${QEMU_SHELL:-}" ]] && [[ -n "$SHELL" ]]; then
+  export QEMU_SHELL=$(basename "$SHELL")
+fi
+
+nixos_config=vm.nix
+if [[ $# -gt 0 ]]; then
+  nixos_config=$1
+  shift
+fi
+export QEMU_NIXOS_CONFIG=$(readlink -f "$nixos_config")
+
+qemu_tty=/dev/null
+tmux_pane_pid=
+if [[ -n "${TMUX:-}" ]] && command -v tmux >/dev/null 2>&1; then
+  tmux_session=($(tmux new-window -P -F '#{pane_tty} #{pane_pid}' "sleep 99999999999"))
+  qemu_tty=${tmux_session[0]}
+  tmux_pane_pid=${tmux_session[1]}
+  export QEMU_OPTS="-nographic -chardev tty,id=pts2,path=$qemu_tty -device isa-serial,chardev=pts2 ${QEMU_OPTS:-}"
+else
+  export QEMU_OPTS="-nographic -serial mon:stdio ${QEMU_OPTS:-}"
+fi
+
+build_succeed=
+cleanup() {
+  if [[ -n "$build_succeed" ]]; then
+    rm -f result
+  fi
+  if [[ -n "$tmux_pane_pid" ]]; then
+    kill "$tmux_pane_pid"
+  fi
+}
+trap cleanup EXIT SIGINT SIGQUIT ERR
+
+export QEMU_OPTS="$QEMU_OPTS -virtfs local,path=/home/,security_model=none,mount_tag=home"
+nix_profile="/nix/var/nix/profiles/per-user/$USER/profile/"
+if [[ -d $nix_profile ]]; then
+  export QEMU_OPTS="$QEMU_OPTS -virtfs local,path=$nix_profile,security_model=none,mount_tag=nixprofile"
+fi
+
+nixos-rebuild -I "nixos-config=$script_dir/../share/nixos-shell/nixos-shell.nix" "$@" build-vm 2>&1 | tee "$qemu_tty"
+build_succeed=1
+./result/bin/run-*-vm

default.nix

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+with import <nixpkgs> {};
+stdenv.mkDerivation {
+  name = "env";
+  src = ./.;
+  buildInputs = [ bash ];
+  preConfigure = ''
+    export PREFIX=$out
+  '';
+}

example-vm.nix

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+{ pkgs, ...}: {
+  boot.kernelPackages = pkgs.linuxPackages_latest;
+  services.openssh.enable = true;
+}

share/nixos-shell/nixos-shell.nix

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+{ lib, config, pkgs, ... }:
+# ./run-vm.sh -I nixos-config=./test-vm.nix
+let
+  home = builtins.getEnv "HOME";
+  user = builtins.getEnv "USER";
+  pwd = builtins.getEnv "PWD";
+  shell = builtins.getEnv "QEMU_SHELL";
+  path = builtins.getEnv "QEMU_PATH";
+  nixos_config = builtins.getEnv "QEMU_NIXOS_CONFIG";
+  term = builtins.getEnv "TERM";
+in {
+  users.extraUsers.root = {
+    # Allow the user to login as root without password.
+    initialHashedPassword = "";
+    shell = pkgs.${shell} or pkgs.bashInteractive;
+    home = lib.mkVMOverride (if home != "" then home else "/root");
+  };
+  services.mingetty.helpLine = ''
+    Log in as "root" with an empty password.
+  '';
+
+  # build-vm overrides our filesystem settings in nixos-config
+  # cache=loose -> bad idea? Well, at least it is fast!1!!
+  boot.initrd.postMountCommands = ''
+    mkdir -p $targetRoot/home
+    mount -t 9p home $targetRoot/home -o trans=virtio,version=9p2000.L,cache=loose
+    ${lib.optionalString (user != "") ''
+      mkdir -p $targetRoot/nix/var/nix/profiles/per-user/${user}/profile/
+      mount -t 9p nixprofile $targetRoot/nix/var/nix/profiles/per-user/${user}/profile/ -o trans=virtio,version=9p2000.L,cache=loose
+    ''}
+  '';
+  environment.loginShellInit = ''
+    # fix terminal size
+    eval "$(${pkgs.xterm}/bin/resize)"
+
+    ${lib.optionalString (pwd != "") "cd '${pwd}' 2>/dev/null"}
+    ${lib.optionalString (term != "") "export TERM='${term}'"}
+    ${lib.optionalString (path != "") "export PATH=${path}:$PATH"}
+  '';
+
+  systemd.services."serial-getty@ttyS0".enable = true;
+  networking.firewall.enable = false;
+
+  imports = lib.optional (nixos_config != "") nixos_config;
+}