smolvm

Ship and run software with isolation by default.

This is a CLI tool that lets you:

1. Manage and run custom Linux virtual machines locally with: sub-second cold start, cross-platform (macOS, Linux), elastic memory usage.
2. Pack a stateful virtual machine into a single file (.smolmachine) to rehydrate on any supported platform.

Install

# install (macOS + Linux)
curl -sSL https://smolmachines.com/install.sh | bash

# for coding agents — install + discover all commands
curl -sSL https://smolmachines.com/install.sh | bash && smolvm --help

Or download from GitHub Releases.

Quick Start

# run a command in an ephemeral VM (cleaned up after exit)
smolvm machine run --net --image alpine -- sh -c "echo 'Hello world from a microVM' && uname -a"

# interactive shell
smolvm machine run --net -it --image alpine -- /bin/sh
# inside the VM: apk add sl && sl && exit

Use This For

Sandbox untrusted code — run untrusted programs in a hardware-isolated VM. Host filesystem, network, and credentials are separated by a hypervisor boundary.

# network is off by default — untrusted code can't phone home
smolvm machine run --image alpine -- ping -c 1 1.1.1.1
# fails — no network access

# lock down egress — only allow specific hosts
smolvm machine run --net --image alpine --allow-host registry.npmjs.org -- wget -q -O /dev/null https://registry.npmjs.org
# works — allowed host

smolvm machine run --net --image alpine --allow-host registry.npmjs.org -- wget -q -O /dev/null https://google.com
# fails — not in allow list

Pack into portable executables — turn any workload into a self-contained binary. All dependencies are pre-baked — no install step, no runtime downloads, boots in <200ms.

smolvm pack create --image python:3.12-alpine -o ./python312
./python312 run -- python3 --version
# Python 3.12.x — isolated, no pyenv/venv/conda needed

Persistent machines for development — create, stop, start. Installed packages survive restarts.

smolvm machine create --net myvm
smolvm machine start --name myvm
smolvm machine exec --name myvm -- apk add sl
smolvm machine exec --name myvm -it -- /bin/sh
# inside: sl, ls, uname -a — type 'exit' to leave
smolvm machine stop --name myvm

Use git and SSH without exposing keys — forward your host SSH agent into the VM. Private keys never enter the guest — the hypervisor enforces this. Requires an SSH agent running on your host (ssh-add -l to check).

smolvm machine run --ssh-agent --net --image alpine -- sh -c "apk add -q openssh-client && ssh-add -l"
# lists your host keys, but they can't be extracted from inside the VM

smolvm machine exec --name myvm -- git clone git@github.com:org/private-repo.git

Declare environments with a Smolfile — reproducible VM config in a simple TOML file.

image = "python:3.12-alpine"
net = true

[network]
allow_hosts = ["api.stripe.com", "db.example.com"]

[dev]
init = ["pip install -r requirements.txt"]
volumes = ["./src:/app"]

[auth]
ssh_agent = true

smolvm machine create myvm -s Smolfile
smolvm machine start --name myvm

More examples: python · node · doom

How It Works

Each workload gets real hardware isolation — its own kernel on Hypervisor.framework (macOS) or KVM (Linux). libkrun VMM with custom kernel: libkrunfw. Pack it into a .smolmachine and it runs anywhere the host architecture matches, with zero dependencies.

Defaults: 4 vCPUs, 8 GiB RAM. Memory is elastic via virtio balloon — the host only commits what the guest actually uses and reclaims the rest automatically. vCPU threads sleep in the hypervisor when idle, so over-provisioning has near-zero cost. Override with --cpus and --mem.

Comparison

	smolvm	Containers	Colima	QEMU	Firecracker	Kata
Isolation	VM per workload	Namespace (shared kernel)	Namespace (1 VM)	Separate VM	Separate VM	VM per container
Boot time	<200ms	~100ms	~seconds	~15-30s	<125ms	~500ms
Architecture	Library (libkrun)	Daemon	Daemon (in VM)	Process	Process	Runtime stack
Per-workload VMs	Yes	No	No (shared)	Yes	Yes	Yes
macOS native	Yes	Via Docker VM	Yes (krunkit)	Yes	No	No
Embeddable SDK	Yes	No	No	No	No	No
Portable artifacts	.smolmachine	Images (need daemon)	No	No	No	No

Platform Support

Host	Guest	Requirements
macOS Apple Silicon	arm64 Linux	macOS 11+
macOS Intel	x86_64 Linux	macOS 11+ (untested)
Linux x86_64	x86_64 Linux	KVM (/dev/kvm)
Linux aarch64	aarch64 Linux	KVM (/dev/kvm)

Known Limitations

• Network is opt-in (--net on machine create). TCP/UDP only, no ICMP.
• Volume mounts: directories only (no single files).
• macOS: binary must be signed with Hypervisor.framework entitlements.
• --ssh-agent requires an SSH agent running on the host (SSH_AUTH_SOCK must be set).

Development

See docs/DEVELOPMENT.md.

Apache-2.0 · made by @binsquare · twitter · github