smolmachines 1.4.4

Embed isolated microVM sandboxes directly in your Python code — local (embedded) or smolfleet cloud.

smol — Python SDK

Embed isolated microVM sandboxes directly in your Python code. Same API locally (embedded engine, no server) or against the smolfleet cloud — the backend is chosen via ConnectOptions / SMOL_CLOUD_TOKEN. Mirrors the Node SDK.

Supported platforms (native local transport): macOS Apple Silicon, and Linux x64/arm64 with glibc ≥ 2.34 (RHEL 9, Ubuntu 22.04+, Debian 12, Amazon Linux 2023; the wheel is tagged manylinux_2_34). The cloud transport works anywhere the wheel installs. Not yet published: macOS Intel, and glibc < 2.34.

from smol import Machine, MachineConfig, ResourceSpec

# Local (embedded microVM) — boots in-process, no server.
with Machine.create(MachineConfig(resources=ResourceSpec(cpus=2, memory_mb=1024, network=True))) as m:
    res = m.run("python:3.12", ["python", "-c", "print(2 ** 10)"])
    res.assert_success()
    print(res.stdout)            # 1024
    m.write_file("/tmp/in.txt", "hi")
    print(m.read_file("/tmp/in.txt").decode())

# Cloud (smolfleet) — same API, just point at the cloud.
from smol import ConnectOptions
with Machine.create(
    MachineConfig(image="alpine:3.20"),
    ConnectOptions(target="cloud", api_key="smk_…"),  # or set SMOL_CLOUD_TOKEN
) as m:
    print(m.exec(["echo", "hi"]).stdout)

Architecture

• Pure-Python layer (python/smol): Machine, transports, types, errors — zero third-party deps (the cloud transport uses only urllib).
• Native core (src/lib.rs, crate smol-py): a pyo3 extension that links the smolvm engine in-process for the local path — the Python analogue of the smol-node NAPI crate. The local API is synchronous (the engine blocks).
• Cloud transport: a REST client to smolfleet /v1 whose request/response shapes match smolfleet's OpenAPI contract (Bearer smk_…).

API

• Machine.create(config=None, conn=None) — create and start a machine.
• machine.exec(command, opts=None) / machine.run(image, command, opts=None) → ExecResult
• machine.read_file(path) → bytes / machine.write_file(path, data, mode=None)
• machine.pull_image(image) / machine.list_images() (local)
• machine.stop() / machine.delete() / machine.state()
• Use it as a context manager to auto-delete() on exit.
• Errors are typed: SmolError (with .code), ExecutionError, NotSupportedError, InvalidConfigError.

ExecResult has .exit_code, .stdout, .stderr, .success, .output, and .assert_success().

Install / build from source

The cloud path is pure Python. The local path needs the native extension, which links libkrun from the sibling smolvm repo (three levels up).

python -m venv .venv && . .venv/bin/activate
pip install maturin
# Build + install the native extension (points at the repo's bundled libkrun):
LIBKRUN_BUNDLE=../../../lib maturin develop

To boot local microVMs the engine needs a code-signed boot helper carrying the macOS com.apple.security.hypervisor entitlement (the Python process itself does not). Point it at one (and the libkrun dir):

SMOLVM_BOOT_BINARY=../../../target/release/smolvm \
SMOLVM_LIB_DIR=../../../lib \
python your_script.py

On Linux the host needs /dev/kvm.

Tests

python tests/test_unit.py        # error parsing + path encoding (no VM/network)
python tests/test_cloud_mock.py  # cloud transport vs a mock /v1 (no VM/network)
# Local VM boot (needs the native build + the env above):
SMOLVM_BOOT_BINARY=… SMOLVM_LIB_DIR=… .venv/bin/python tests/test_local_e2e.py

License

Apache-2.0