Sandboxed Execution with Shuru

Shuru boots an ephemeral Linux microVM (Debian, ARM64) on macOS. Each shuru run gets a fresh disk clone - all changes are discarded on exit. Use it whenever you need to run commands in isolation from the host.

Core Workflow

The pattern is: run in sandbox, mount to share files, checkpoint to persist state.

# 1. Run a command in a fresh VM
shuru run -- echo "hello from the sandbox"

# 2. Mount the project directory so the VM can access host files
shuru run --mount ./src:/workspace -- ls /workspace

# 3. If the command needs network access (install packages, fetch data)
shuru run --allow-net -- sh -c 'apt-get install -y curl && curl https://example.com'

# 4. If setup is expensive, save a checkpoint and reuse it
shuru checkpoint create node-env --allow-net -- apt-get install -y nodejs npm
shuru run --from node-env --mount .:/workspace -- node /workspace/app.js

Command Chaining

Chain commands with sh -c when you need multiple steps:

shuru run --allow-net -- sh -c 'apt-get install -y python3 python3-pip && python3 -c "print(1+1)"'

shuru run --mount .:/workspace -- sh -c 'cd /workspace && ls -la && cat README.md'

Essential Commands

Run

shuru run [flags] [-- command...]

# Interactive shell (default when no command given)
shuru run

# Run a single command
shuru run -- whoami

# With resources
shuru run --cpus 4 --memory 4096 --disk-size 8192 -- make -j4

# With networking + port forwarding
shuru run --allow-net -p 8080:80 -- nginx -g 'daemon off;'

# Multiple mounts
shuru run --mount ./src:/src --mount ./data:/data -- ls /src /data

# From a checkpoint
shuru run --from myenv -- npm test

Checkpoints

# Create: boots VM, runs command, saves disk on exit
shuru checkpoint create <name> [flags] [-- command...]

# Stack: create from an existing checkpoint
shuru checkpoint create with-deps --from base-env --allow-net -- npm install

# List all checkpoints (shows actual disk usage)
shuru checkpoint list

# Delete
shuru checkpoint delete <name>

Checkpoint names must be unique - delete the old one before re-creating with the same name.

Other Commands

# Download/update OS image
shuru init
shuru init --force    # re-download even if up to date

# Upgrade CLI + OS image
shuru upgrade

# Clean up leftover data from crashed VMs
shuru prune

Common Patterns

Dev Environment Setup

Create a checkpoint with all dependencies pre-installed, then use it for fast runs:

# One-time setup
shuru checkpoint create python-dev --allow-net -- sh -c 'apt-get install -y python3 python3-pip && pip install pytest requests'

# Fast subsequent runs
shuru run --from python-dev --mount .:/workspace -- sh -c 'cd /workspace && pytest'

Testing Untrusted Code

Run untrusted scripts with no network access and no host filesystem access:

# Fully isolated — no --allow-net, no --mount
shuru run -- sh -c 'echo "malicious script here" && rm -rf / 2>/dev/null; echo "host is safe"'

Build and Test

Mount source, build inside the VM, results appear on host via the mount:

shuru run --mount .:/workspace --cpus 4 --memory 4096 -- sh -c '
  cd /workspace
  apt-get install -y build-essential
  make -j4
  make test
'

Port Forwarding for Web Servers

shuru run --allow-net --from node-env -p 3000:3000 --mount .:/app -- sh -c '
  cd /app && node server.js
'
# Access at http://localhost:3000 on the host

Stacking Checkpoints

Build environments incrementally:

shuru checkpoint create base --allow-net -- apt-get install -y build-essential git curl
shuru checkpoint create node --from base --allow-net -- apt-get install -y nodejs npm
shuru checkpoint create project --from node --allow-net --mount .:/app -- sh -c 'cd /app && npm install'
# Now "project" has OS deps + Node + node_modules baked in
shuru run --from project --mount .:/app -- sh -c 'cd /app && npm test'

Project Config (shuru.json)

Place shuru.json in the project root to avoid repeating flags:

{
  "cpus": 2,
  "memory": 2048,
  "disk_size": 4096,
  "allow_net": true,
  "ports": ["8080:80"],
  "mounts": ["./src:/workspace"],
  "command": ["/bin/sh", "-c", "cd /workspace && sh"],
  "secrets": {
    "API_KEY": {
      "from": "OPENAI_API_KEY",
      "hosts": ["api.openai.com"]
    }
  },
  "network": {
    "allow": ["api.openai.com", "registry.npmjs.org"]
  }
}

CLI flags override config values. When secrets are configured, the guest receives placeholder tokens and the proxy substitutes real values on HTTPS requests to allowed hosts. See references/config.md for all fields.

Important Constraints

Networking is off by default. You must pass --allow-net to install packages or make HTTP requests.
The guest is Debian Linux (aarch64). Use apt-get install for packages.
Ephemeral by default. Everything is discarded on exit unless you checkpoint.
Mounts are read-write. Changes to mounted directories are visible on the host immediately.
macOS only (Apple Silicon). Uses Apple Virtualization.framework.
Default resources: 2 CPUs, 2048 MB RAM, 4096 MB disk. Override with --cpus, --memory, --disk-size.

Deep-Dive Documentation

references/checkpoints.md — checkpoint lifecycle, stacking, disk usage
references/config.md — shuru.json fields and resolution order
references/networking.md — allow-net, port forwarding, proxy behavior

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