add firecracker-vm package

pkgs/firecracker-vm/default.nix

@@ -0,0 +1,32 @@
+{ callPackage
+, firecracker
+, writeShellScriptBin
+, writeText
+}:
+
+let
+  kernel = callPackage ./kernel.nix { };
+  rootfs = callPackage ./rootfs.nix { };
+
+  vmconfig = writeText "vmconfig.json" (builtins.toJSON {
+    boot-source = {
+      kernel_image_path = "${kernel}/vmlinux";
+      boot_args = "panic=1 console=ttyS0 ro";
+    };
+    drives = [
+      {
+        drive_id = "rootfs";
+        path_on_host = rootfs;
+        is_root_device = true;
+        is_read_only = true;
+      }
+    ];
+    machine-config.vcpu_count = 2;
+    machine-config.mem_size_mib = 1024;
+    network-interfaces = [ ];
+  });
+
+in
+writeShellScriptBin "firecracker-vm" ''
+  ${firecracker}/bin/firecracker --no-api --config-file ${vmconfig}
+''

pkgs/firecracker-vm/kernel.nix

@@ -0,0 +1,34 @@
+{ fetchFromGitHub
+, linuxManualConfig
+, linux_6_1
+, kernel ? linux_6_1
+}:
+
+let
+  fcsrc = fetchFromGitHub {
+    owner = "firecracker-microvm";
+    repo = "firecracker";
+    rev = "e1c351bdde745d33858e04089eef6e2279b286fd";
+    hash = "sha256-LvVqA5jBKWQYeV9OHrrb+1gmAqHxDszeVBhFwweDrmo=";
+  };
+
+  shortVer = builtins.head (
+    builtins.match
+      "([0-9]+\.[0-9]+).*"
+      kernel.version
+  );
+
+in
+(linuxManualConfig {
+
+  inherit (kernel) src version;
+  configfile =
+    "${fcsrc}/resources/guest_configs/microvm-kernel-ci-x86_64-${shortVer}.config";
+
+}).overrideAttrs (o: {
+
+  postInstall = (o.postInstall or "") + ''
+    cp vmlinux $out/
+  '';
+
+})

pkgs/firecracker-vm/rootfs.nix

@@ -0,0 +1,29 @@
+{ e2fsprogs
+, pkgsStatic
+, runCommand
+, util-linux
+, writeShellScript
+}:
+
+let
+  init-sh = builtins.toFile "init.sh" ''
+    #!/bin/sh
+    mount none -t proc /proc
+    mount none -t sysfs /sys
+    mount none -t tmpfs /tmp
+    mount none -t tmpfs /run
+    exec sh
+  '';
+
+  mkroot = writeShellScript "mkroot" ''
+    mkdir -p rootfs/{dev,proc,run,sys,tmp}
+    install -Dm 755 ${init-sh} rootfs/sbin/init
+    install -Dm 755 ${pkgsStatic.busybox}/bin/busybox rootfs/bin/busybox
+    chroot rootfs /bin/busybox --install -s /bin
+    ${e2fsprogs.bin}/bin/mkfs.ext4 -d rootfs $out 32M
+  '';
+
+in
+runCommand "rootfs.img" { } ''
+  ${util-linux}/bin/unshare -r ${mkroot}
+''