Initial Commit

main.go

@@ -0,0 +1,256 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+const (
+	rootDir   = "/var/lib/microvm"
+	imageDir  = rootDir + "/images"
+	vmDirBase = rootDir + "/vms"
+
+	defaultImgURL  = "https://cloud-images.ubuntu.com/noble/current/noble-server-cloudimg-amd64.img"
+	defaultImgName = "ubuntu-24.04-cloudinit.qcow2"
+
+	memMB = "1024"
+	cpus  = "1"
+)
+
+func ensureDirs() {
+	for _, d := range []string{imageDir, vmDirBase} {
+		if err := os.MkdirAll(d, 0755); err != nil {
+			panic(err)
+		}
+	}
+}
+
+func baseImagePath() string {
+	return filepath.Join(imageDir, defaultImgName)
+}
+
+func vmDir(name string) string   { return filepath.Join(vmDirBase, name) }
+func pidFile(name string) string { return filepath.Join(vmDir(name), "vm.pid") }
+func diskPath(name string) string {
+	return filepath.Join(vmDir(name), "disk.qcow2")
+}
+func seedISOPath(name string) string {
+	return filepath.Join(vmDir(name), "seed.iso")
+}
+
+func sshPort(name string) int {
+	if strings.HasPrefix(name, "vm") {
+		if n, err := strconv.Atoi(strings.TrimPrefix(name, "vm")); err == nil {
+			return 2220 + n
+		}
+	}
+	return 2222
+}
+
+func readSSHPublicKey() string {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		panic(err)
+	}
+
+	keys := []string{
+		filepath.Join(home, ".ssh", "id_ed25519.pub"),
+		filepath.Join(home, ".ssh", "id_rsa.pub"),
+	}
+
+	for _, k := range keys {
+		if data, err := os.ReadFile(k); err == nil {
+			return strings.TrimSpace(string(data))
+		}
+	}
+
+	panic("no SSH public key found in ~/.ssh")
+}
+
+func createCloudInitSeed(name string) {
+	sshKey := readSSHPublicKey()
+
+	userData := fmt.Sprintf(`#cloud-config
+users:
+  - name: ubuntu
+    sudo: ALL=(ALL) NOPASSWD:ALL
+    shell: /bin/bash
+    ssh_authorized_keys:
+      - %s
+
+ssh_pwauth: false
+disable_root: true
+`, sshKey)
+
+	metaData := fmt.Sprintf(`instance-id: %s
+local-hostname: %s
+`, name, name)
+
+	tmpDir, err := os.MkdirTemp("", "cloudinit")
+	if err != nil {
+		panic(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	userDataPath := filepath.Join(tmpDir, "user-data")
+	metaDataPath := filepath.Join(tmpDir, "meta-data")
+
+	os.WriteFile(userDataPath, []byte(userData), 0644)
+	os.WriteFile(metaDataPath, []byte(metaData), 0644)
+
+	cmd := exec.Command(
+		"genisoimage",
+		"-output", seedISOPath(name),
+		"-volid", "cidata",
+		"-joliet",
+		"-rock",
+		userDataPath,
+		metaDataPath,
+	)
+
+	if out, err := cmd.CombinedOutput(); err != nil {
+		panic("cloud-init ISO creation failed:\n" + string(out))
+	}
+}
+
+func ensureBaseImage() {
+	if _, err := os.Stat(baseImagePath()); err == nil {
+		return
+	}
+
+	fmt.Println("Downloading Ubuntu 24.04 cloud image...")
+
+	resp, err := http.Get(defaultImgURL)
+	if err != nil {
+		panic(err)
+	}
+	defer resp.Body.Close()
+
+	out, err := os.Create(baseImagePath())
+	if err != nil {
+		panic(err)
+	}
+	defer out.Close()
+
+	if _, err := io.Copy(out, resp.Body); err != nil {
+		panic(err)
+	}
+}
+
+func createVM(name string) {
+	ensureBaseImage()
+	os.MkdirAll(vmDir(name), 0755)
+
+	cmd := exec.Command(
+		"qemu-img", "create",
+		"-f", "qcow2",
+		"-F", "qcow2",
+		"-b", baseImagePath(),
+		diskPath(name),
+	)
+
+	if out, err := cmd.CombinedOutput(); err != nil {
+		panic(string(out))
+	}
+
+	createCloudInitSeed(name)
+
+	fmt.Println("VM created:", name)
+}
+
+func startVM(name string) {
+	if data, err := os.ReadFile(pidFile(name)); err == nil {
+		pid := strings.TrimSpace(string(data))
+		if _, err := os.Stat("/proc/" + pid); err == nil {
+			panic("VM already running")
+		}
+		os.Remove(pidFile(name))
+	}
+
+	port := sshPort(name)
+
+	cmd := exec.Command(
+	    "qemu-system-x86_64",
+	    "-enable-kvm",
+	    "-machine", "q35",
+	    "-cpu", "host",
+	    "-m", memMB,
+	    "-smp", cpus,
+
+	    // VNC-only console
+	    "-vga", "virtio",
+	    "-display", "vnc=0.0.0.0:1",
+
+	    // Main disk (cloud image)
+	    "-drive", fmt.Sprintf("file=%s,if=virtio,format=qcow2", diskPath(name)),
+
+	    // Cloud-init seed ISO
+	    "-drive", fmt.Sprintf("file=%s,if=virtio,format=raw", seedISOPath(name)),
+
+	    // User-mode networking + SSH forward
+	    "-netdev", fmt.Sprintf("user,id=net0,hostfwd=tcp::%d-:22", port),
+	    "-device", "virtio-net-pci,netdev=net0",
+
+	    // Boot from disk (GRUB inside image)
+	    "-boot", "order=c",
+
+	    "-pidfile", pidFile(name),
+	    "-daemonize",
+	)
+
+
+	if out, err := cmd.CombinedOutput(); err != nil {
+		panic("qemu failed:\n" + string(out))
+	}
+
+	fmt.Println("VM started:", name)
+	fmt.Printf("VNC: localhost:5901\n")
+	fmt.Printf("SSH: ssh ubuntu@localhost -p %d\n", port)
+}
+
+func stopVM(name string) {
+	data, err := os.ReadFile(pidFile(name))
+	if err != nil {
+		panic("VM not running")
+	}
+	pid := strings.TrimSpace(string(data))
+	exec.Command("kill", pid).Run()
+	os.Remove(pidFile(name))
+	fmt.Println("VM stopped:", name)
+}
+
+func listVMs() {
+	entries, _ := os.ReadDir(vmDirBase)
+	for _, e := range entries {
+		fmt.Println(e.Name())
+	}
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("usage: microvm <create|start|stop|list> <name>")
+		os.Exit(1)
+	}
+
+	ensureDirs()
+
+	switch os.Args[1] {
+	case "create":
+		createVM(os.Args[2])
+	case "start":
+		startVM(os.Args[2])
+	case "stop":
+		stopVM(os.Args[2])
+	case "list":
+		listVMs()
+	default:
+		fmt.Println("usage: microvm <create|start|stop|list> <name>")
+	}
+}
+