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WASM Cloud Lab — File Inventory & Build Documentation

Overview

This project runs a full x86 PC emulator (v86) directly in the browser using WebAssembly. It boots a real Linux kernel with a minimal userspace — all client-side, no server-side compute resources are used after the static files are served.

The environment currently runs Buildroot Linux (kernel 6.8.12) because the original Alpine Linux image URLs referenced in the first version of this page were 404 Not Found, and building the v86 Alpine image requires a running Docker daemon (see Alpine section below).

Downloaded Files

All binaries are fetched from the v86 project's own CDN (copy.sh / i.copy.sh) and served locally to avoid CORS and availability issues.

1. v86 WebAssembly Engine

File Source URL Local Path Size SHA-256
libv86.js https://copy.sh/v86/build/libv86.js v86/build/libv86.js 337,697 B 3a64f4dfef4f6ada802aa38bd05b1caf534fa3ca085c6ea297673a11d13b93df
v86.wasm https://copy.sh/v86/build/v86.wasm v86/build/v86.wasm 1,424,184 B 93247ff03ed46dddf64fc7d2363a25858a76d22cb82c02a08df5c399ae03e2dd

What it is: The v86 emulator compiled to JavaScript and WebAssembly. libv86.js is the loader/runtime; v86.wasm is the compiled Rust/C core that does the actual x86 emulation.

2. PC Firmware (BIOS / VGA BIOS)

File Source URL Local Path Size SHA-256
seabios.bin https://copy.sh/v86/bios/seabios.bin v86/bios/seabios.bin 131,072 B 73e3f359102e3a9982c35fce98eb7cd08f18303ac7f1ba6ebfbe6cdc1c244d98
vgabios.bin https://copy.sh/v86/bios/vgabios.bin v86/bios/vgabios.bin 36,352 B a4bc0d80cc3ca028c73dafa8fee396b8d054ce87ebd8abfbd31b06b437607880

What it is: SeaBIOS (open-source x86 BIOS) and the Bochs VGA BIOS. v86 needs these ROM images to initialize the virtual motherboard, CPU, memory map, and VGA adapter before it can load an operating system.

3. Linux Kernel Image

File Source URL Local Path Size SHA-256
buildroot-bzimage68.bin https://i.copy.sh/buildroot-bzimage68.bin v86/images/binaries/buildroot-bzimage68.bin 10,068,480 B 507a759c70ab7a490a233be454d0b5b88bc667956a410b531cb4edc091e2eb1c

What it is: A pre-built Buildroot Linux kernel (bzImage format, version 6.8.12, built Sat Aug 31 22:58:35 UTC 2024). This is a standalone kernel that contains an embedded initramfs with a minimal BusyBox-based userspace. It is one of the standard test images shipped by the v86 project.

Verification:

file buildroot-bzimage68.bin
# → Linux kernel x86 boot executable bzImage, version 6.8.12 ...

How the Environment Is Built

Buildroot Linux Image

The buildroot-bzimage68.bin image is not built in this project — it is downloaded as a pre-built artifact from the v86 project. However, if you wanted to reproduce a similar image from scratch, the upstream process is:

  1. Toolchain: Buildroot uses a cross-compilation toolchain (typically i686-buildroot-linux-musl or i686-buildroot-linux-gnu).
  2. Kernel: Configures and compiles Linux 6.8.12 for x86 with essential drivers (IDE, VGA framebuffer, serial, NE2000/virtio-net).
  3. Rootfs: Compiles BusyBox and selected packages into a minimal root filesystem.
  4. Packaging: The rootfs is bundled into the kernel as an initramfs (cpio archive) so the entire OS fits in a single bzImage file. No separate disk image is required.

The v86 project publishes these pre-built kernels at https://i.copy.sh/ for quick testing.

v86 Engine Build

The v86 engine itself is built from the official repository:

git clone https://github.com/copy/v86.git
cd v86
make all

Requirements:

  • Rust with wasm32-unknown-unknown target
  • clang compatible with Rust
  • nodejs (for build tooling)
  • make

This produces:

  • build/libv86.js — browser-ready loader
  • build/v86.wasm — WebAssembly bytecode

We download the already-compiled release artifacts instead of building from source.

Server Setup

A minimal Python HTTPS server is used to serve the files on port 9999, binding to 0.0.0.0 so it is reachable from outside:

# Self-signed certificate (required for HTTPS)
openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 1 -nodes -subj "/CN=localhost"

# Start server
python3 server.py

The server script (server.py) is a plain http.server.HTTPServer wrapped in TLS. It serves the current directory (and all subdirectories) so wasm_lab.html, v86/build/*, v86/bios/*, and v86/images/* are all reachable.

Access: https://<host-ip>:9999/wasm_lab.html

⚠️ Because the certificate is self-signed, browsers will show a security warning. Accept the risk / click "Advanced" → "Proceed" to continue.

Alpine Linux — Why Not Used

The original HTML claimed to run "Alpine Linux". The correct way to create a v86-compatible Alpine image is documented in the v86 repository at tools/docker/alpine/:

  1. Build a Docker image from i386/alpine:3.21.0
  2. Export the container filesystem to a tar archive
  3. Run tools/fs2json.py --zstd to generate alpine-fs.json
  4. Run tools/copy-to-sha256.py --zstd to generate alpine-rootfs-flat/
  5. Serve those files alongside the kernel

We could not use Alpine in this environment because:

  • The pre-built Alpine image URLs (https://copy.sh/v86/images/binaries/bzImage-ix86-3.16.bin, etc.) referenced in older examples are 404 Not Found.
  • Building the v86 Alpine image requires a running Docker daemon (docker build --platform linux/386 ...).
  • This host does not have a functional Docker daemon available (dockerd is missing / not running).

Therefore we switched to the Buildroot Linux image (buildroot-bzimage68.bin), which is readily available, fully self-contained, and boots without any additional filesystem infrastructure.

Disk Space Summary

Category Size
v86 engine (JS + WASM) ~1.8 MB
BIOS ROMs ~167 KB
Buildroot Linux kernel ~9.6 MB
Total static assets ~11.6 MB

References