feat: arch-aware downloads in create-build and fetch-busybox target (#2260)

* feat: arch-aware downloads in create-build and fetch-busybox target

- Update setupKernel/setupFC to use arch-prefixed URLs with legacy fallback
- Add errNotFound sentinel for 404 handling in download helper
- Use atomic temp-file writes to avoid partial downloads
- Add fetch-busybox Makefile target to swap busybox binary for ARM64 builds

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: commit both amd64 and arm64 busybox binaries with build tags

Replace the single x86-64 busybox binary + fetch-busybox Makefile hack
with two architecture-specific binaries selected via Go build tags.
GOARCH automatically picks the right binary at compile time.

- busybox_amd64: existing x86-64 static binary (renamed)
- busybox_arm64: aarch64 static binary
- busybox_amd64.go / busybox_arm64.go: build-tag-gated embeds
- Remove fetch-busybox Makefile target (no longer needed)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: rename busybox binaries with version, add source comments

Per review: keep version in filename (busybox_1.36.1-2_{arch}) and
document the package source in the Go embed files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: e2b <e2b@Onsites-MacBook-Pro.local>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

packages/orchestrator/cmd/create-build/main.go

@@ -414,71 +414,141 @@ func printLocalFileSizes(basePath, buildID string) {
 }
 
 func setupKernel(ctx context.Context, dir, version string) error {
-	dstPath := filepath.Join(dir, version, "vmlinux.bin")
+	arch := utils.TargetArch()
+	dstPath := filepath.Join(dir, version, arch, "vmlinux.bin")
+
 	if err := os.MkdirAll(filepath.Dir(dstPath), 0o755); err != nil {
 		return fmt.Errorf("mkdir kernel dir: %w", err)
 	}
 
 	if _, err := os.Stat(dstPath); err == nil {
-		fmt.Printf("✓ Kernel %s exists\n", version)
+		fmt.Printf("✓ Kernel %s (%s) exists\n", version, arch)
 
 		return nil
 	}
 
-	kernelURL, _ := url.JoinPath("https://storage.googleapis.com/e2b-prod-public-builds/kernels/", version, "vmlinux.bin")
-	fmt.Printf("⬇ Downloading kernel %s...\n", version)
+	// Try arch-specific URL first: {version}/{arch}/vmlinux.bin
+	archURL, err := url.JoinPath("https://storage.googleapis.com/e2b-prod-public-builds/kernels/", version, arch, "vmlinux.bin")
+	if err != nil {
+		return fmt.Errorf("invalid kernel URL: %w", err)
+	}
+
+	fmt.Printf("⬇ Downloading kernel %s (%s)...\n", version, arch)
+
+	if err := download(ctx, archURL, dstPath, 0o644); err == nil {
+		return nil
+	} else if !errors.Is(err, errNotFound) {
+		return fmt.Errorf("failed to download kernel: %w", err)
+	}
+
+	// Legacy URLs are x86_64-only; only fall back for amd64.
+	if arch != "amd64" {
+		return fmt.Errorf("kernel %s not found for %s (no legacy fallback for non-amd64)", version, arch)
+	}
+
+	legacyURL, err := url.JoinPath("https://storage.googleapis.com/e2b-prod-public-builds/kernels/", version, "vmlinux.bin")
+	if err != nil {
+		return fmt.Errorf("invalid kernel legacy URL: %w", err)
+	}
+
+	fmt.Printf("  %s path not found, trying legacy URL...\n", arch)
 
-	return download(ctx, kernelURL, dstPath, 0o644)
+	return download(ctx, legacyURL, dstPath, 0o644)
 }
 
 func setupFC(ctx context.Context, dir, version string) error {
-	dstPath := filepath.Join(dir, version, "firecracker")
+	arch := utils.TargetArch()
+	dstPath := filepath.Join(dir, version, arch, "firecracker")
+
 	if err := os.MkdirAll(filepath.Dir(dstPath), 0o755); err != nil {
 		return fmt.Errorf("mkdir firecracker dir: %w", err)
 	}
 
 	if _, err := os.Stat(dstPath); err == nil {
-		fmt.Printf("✓ Firecracker %s exists\n", version)
+		fmt.Printf("✓ Firecracker %s (%s) exists\n", version, arch)
 
 		return nil
 	}
 
-	// Old releases in https://github.com/e2b-dev/fc-versions/releases don't build
-	// x86_64 and aarch64 binaries. They just build the former and the asset's name
-	// is just 'firecracker'
-	// TODO: Drop this work-around once we remove support for Firecracker v1.10
-	assetName := "firecracker-amd64"
-	if strings.HasPrefix(version, "v1.10") {
-		assetName = "firecracker"
+	// Download from GCS bucket with {version}/{arch}/firecracker path
+	fcURL, err := url.JoinPath("https://storage.googleapis.com/e2b-prod-public-builds/fc-versions/", version, arch, "firecracker")
+	if err != nil {
+		return fmt.Errorf("invalid Firecracker URL: %w", err)
 	}
-	fcURL := fmt.Sprintf("https://github.com/e2b-dev/fc-versions/releases/download/%s/%s", version, assetName)
-	fmt.Printf("⬇ Downloading Firecracker %s...\n", version)
 
-	return download(ctx, fcURL, dstPath, 0o755)
+	fmt.Printf("⬇ Downloading Firecracker %s (%s)...\n", version, arch)
+
+	if err := download(ctx, fcURL, dstPath, 0o755); err == nil {
+		return nil
+	} else if !errors.Is(err, errNotFound) {
+		return fmt.Errorf("failed to download Firecracker: %w", err)
+	}
+
+	// Legacy URLs are x86_64-only; only fall back for amd64.
+	if arch != "amd64" {
+		return fmt.Errorf("firecracker %s not found for %s (no legacy fallback for non-amd64)", version, arch)
+	}
+
+	legacyURL, err := url.JoinPath("https://storage.googleapis.com/e2b-prod-public-builds/fc-versions/", version, "firecracker")
+	if err != nil {
+		return fmt.Errorf("invalid Firecracker legacy URL: %w", err)
+	}
+
+	fmt.Printf("  %s path not found, trying legacy URL...\n", arch)
+
+	return download(ctx, legacyURL, dstPath, 0o755)
 }
 
-func download(ctx context.Context, url, path string, perm os.FileMode) error {
-	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+var errNotFound = errors.New("not found")
+
+func download(ctx context.Context, rawURL, path string, perm os.FileMode) error {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, rawURL, nil)
+	if err != nil {
+		return fmt.Errorf("invalid download URL %s: %w", rawURL, err)
+	}
+
 	resp, err := (&http.Client{Timeout: 5 * time.Minute}).Do(req)
 	if err != nil {
 		return err
 	}
 	defer resp.Body.Close()
 
+	if resp.StatusCode == http.StatusNotFound {
+		return fmt.Errorf("%w: %s", errNotFound, rawURL)
+	}
 	if resp.StatusCode != http.StatusOK {
-		return fmt.Errorf("HTTP %d: %s", resp.StatusCode, url)
+		return fmt.Errorf("HTTP %d: %s", resp.StatusCode, rawURL)
 	}
 
-	f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, perm)
+	// Write to a temporary file and rename atomically to avoid partial files
+	// on network errors or disk-full conditions.
+	tmpPath := path + ".tmp"
+
+	f, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, perm)
 	if err != nil {
 		return err
 	}
-	defer f.Close()
 
-	_, err = io.Copy(f, resp.Body)
-	if err == nil {
-		fmt.Printf("✓ Downloaded %s\n", filepath.Base(path))
+	if _, err := io.Copy(f, resp.Body); err != nil {
+		f.Close()
+		os.Remove(tmpPath)
+
+		return err
 	}
 
-	return err
+	if err := f.Close(); err != nil {
+		os.Remove(tmpPath)
+
+		return err
+	}
+
+	if err := os.Rename(tmpPath, path); err != nil {
+		os.Remove(tmpPath)
+
+		return err
+	}
+
+	fmt.Printf("✓ Downloaded %s\n", filepath.Base(path))
+
+	return nil
 }

packages/orchestrator/pkg/template/build/core/systeminit/busybox.go

@@ -0,0 +1,11 @@
+//go:build amd64
+
+// Busybox v1.36.1 static binary for amd64 (musl, minimal ~16 applets).
+// Custom build added in #1002 — origin unknown, no distro tag in binary.
+
+package systeminit
+
+import _ "embed"
+
+//go:embed busybox_1.36.1-2_amd64
+var BusyboxBinary []byte

…e/build/core/systeminit/busybox_1.36.1-2 …d/core/systeminit/busybox_1.36.1-2_amd64packages/orchestrator/pkg/template/build/core/systeminit/busybox_1.36.1-2 renamed to packages/orchestrator/pkg/template/build/core/systeminit/busybox_1.36.1-2_amd64 packages/orchestrator/pkg/template/build/core/systeminit/busybox_1.36.1-2 renamed to packages/orchestrator/pkg/template/build/core/systeminit/busybox_1.36.1-2_amd64

@@ -0,0 +1,12 @@
+//go:build arm64
+
+// Busybox v1.36.1 static binary for arm64 (glibc, full 271 applets).
+// Source: Debian busybox-static 1:1.36.1-9 (https://packages.debian.org/busybox-static)
+// TODO: rebuild both binaries from the same minimal config for consistency.
+
+package systeminit
+
+import _ "embed"
+
+//go:embed busybox_1.36.1-2_arm64
+var BusyboxBinary []byte