Show HN: Kern – container and resource runtime in a 1.5 MB binary, no daemon

Kern, a new open-source container and resource runtime, launches as a single 1.52 MB static binary with no daemon, capable of starting a kernel-enforced, rootless container in about 3.5 ms. The Rust-based tool, which depends only on libc, supports OCI images, Docker-compatible formats, resource profiles, and an MCP server for AI agents, targeting untrusted and AI-generated code workloads. Its creator positions it as a lightweight alternative to Docker and Podman, while acknowledging limitations such as reliance on user namespaces and lack of hypervisor isolation.

kern: A fast, rootless sandbox and virtual resource runtime for any workload, including untrusted and AI-generated code. A real, kernel-enforced container in ~3.5 ms, out of one 1.52 MB binary with no daemon. 0 RAM at rest · no daemon, no socket, nothing to start · one static binary, libc its only Rust dependency install the release binary static, 1.52 MB, checksum-verified by the script curl -fsSL https://raw.githubusercontent.com/getkern/kern/main/install.sh | sh a throwaway shell in a real OCI image: rootless, kernel-enforced, a few ms kern box dev --image alpine -it -- sh No native Windows: use WSL2. Install. One binary that manages resources, of which isolation is the first. That is why there is no single row for kern in a comparison table: it is a container runtime, a sandbox, a resource slicer and a stack runner at once, in 1.52 MB with no daemon. A real container. Real OCI images: pull , build from a Dockerfile, commit , push , save / load . A box from an image starts in ~3.5 ms. A sandbox, always rootless. User, PID, mount, network, UTS and IPC namespaces, an overlay or read-only root pivoted in, a deny-by-default seccomp allowlist and cgroup v2 limits. One flag, --security-profile untrusted , is the whole hardened bundle. Resource profiles, not just isolation. CPU vcpu: , memory, disk vdisk: and devices vgpio: , declared once in a kern.toml and attached by name. kern run applies the same caps to a process on the host, with no sandbox at all. docs/RESOURCES.md /getkern/kern/blob/main/docs/RESOURCES.md Stacks, in kern's own format or in Docker's. kern compose <file up takes a kern-compose.toml box.NAME tables, with the resource profiles above or the docker-compose.yml you already have, read as written. One stack to one pod, services reaching each other by name. The tools around them. ps , logs , exec , stats , inspect , wait , top a live TUI , doctor , plus a Python and Node SDK and an MCP server for agents. Its entire Rust dependency tree is libc : JSON and OCI manifests are parsed by hand, and pull shells out to the curl and tar already on the machine rather than linking a TLS stack. 1.52 MB is the size-optimized release build; a plain cargo install from source is 1.91 MB. - Not a hypervisor. The boundary is the Linux kernel, so a kernel privilege-escalation bug is an escape. Docker and Podman share that condition, which is why gVisor and Firecracker exist.Read with the tagline, that is one line seen from both sides: untrusted and AI-generated code is what kern is FOR, because you chose to run it and own the blast radius agent tool-calls, CI jobs, build steps, code cells . What it is not for is hostile code from strangers, multi-tenant, on a kernel you serve other tenants from. kern does start rootless always, where Docker's is opt-in. - Not free of the userns trade. Its isolation is built on an unprivileged user namespace, a fertile source of kernel LPE bugs. SECURITY.md /getkern/kern/blob/main/SECURITY.md states this before any claim. - Not a wall around what you mount in. -v $HOME:/host gives the box your home directory: a mount is a trust decision you make, not a boundary kern enforces. --net host and --privileged are opt-outs by name. The one path kern refuses to bind is its own runtime registry. - Not a Docker Engine reimplementation. It speaks Docker's formats , not its API: no overlay networks, no plugins, no Swarm. Matrix: docs/DOCKER-COMPAT.md /getkern/kern/blob/main/docs/DOCKER-COMPAT.md . - Not a Kubernetes runtime. No CRI. Use containerd or CRI-O. - Not shipping GPU slices. On the roadmap /getkern/kern/blob/main/ROADMAP.md , with no GPU code in this edition, so there is nothing here to trust or to attack yet. What it does not know or does not do yet is in OPEN ITEMS.md /getkern/kern/blob/main/OPEN ITEMS.md rather than left for you to find. kern needs a Linux kernel with unprivileged user namespaces and cgroup v2. It runs on Linux, WSL2 and ARM boards Raspberry Pi · Jetson · Arduino UNO Q ; there is no native Windows build, use WSL2 kern ships a pre-baked WSL rootfs . The quickest route is the release binary: one static file, no toolchain, and the script verifies its SHA256 before installing it. curl -fsSL https://raw.githubusercontent.com/getkern/kern/main/install.sh | sh It picks x86 64 or aarch64 for you, installs to ~/.local/bin /usr/local/bin as root, or KERN INSTALL DIR , and refuses to install a download whose checksum does not match. Verifying by hand instead is two lines: curl -fsSLO https://github.com/getkern/kern/releases/latest/download/kern-x86 64-unknown-linux-musl.tar.gz{,.sha256} sha256sum -c kern-x86 64-unknown-linux-musl.tar.gz.sha256 && tar xzf kern-x86 64-unknown-linux-musl.tar.gz From source is the other route, and the whole dependency tree is one crate libc , so it is short: clone, build and install took 36 s on a desktop i7-14700KF , longer on a small ARM board. if you do not have Rust yet curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh cargo install --git https://github.com/getkern/kern getkern --locked That puts kern in ~/.cargo/bin , which rustup adds to your PATH open a new shell, or source "$HOME/.cargo/env" , if kern is not found . The release also ships an aarch64 binary, a Windows .exe shim and a pre-baked WSL rootfs, each with its own .sha256 ; the tag is GPG-signed and independently timestamped provenance/ /getkern/kern/blob/main/provenance . kern doctor tells you whether boxes will run here before you try. Boards, WSL2 and the long form: docs/INSTALL.md /getkern/kern/blob/main/docs/INSTALL.md . Common questions Docker, bubblewrap, youki, E2B, Windows, the threat model : docs/FAQ.md /getkern/kern/blob/main/docs/FAQ.md . kern box dev --image alpine -it -- sh a throwaway shell in a real OCI image kern run --memory 256M --cpus 0.5 -- ./crunch cap a process, no sandbox kern box svc --image nginx:alpine -d -p 8080:80 \ a service: published, restarted, health-checked --restart --health-cmd 'wget -qO- localhost:80' -- nginx -g 'daemon off;' kern ps what is running, with PORTS and HEALTH kern exec svc -it -- sh shell into it kern stop svc its signal, its grace, then the code it exited with kern top live TUI: boxes, CPU/RAM, profiles, volumes kern compose stack.toml up a multi-box stack examples/ or a compose.yml kern compose stack.toml down and take it down again Untrusted code, one flag for the bundle: kern box job --image python:3.12-slim --security-profile untrusted --memory 256m \ -v ./job:/w -- python3 /w/x.py --security-profile untrusted is the seccomp allowlist + --cap-drop ALL + --read-only in one opt-in flag spell them out by hand if you prefer ; add --require-limits to refuse to start unless the memory/pids caps are actually enforced. No network unless you ask, dangerous capabilities dropped, seccomp always on. Ninety runnable examples, each doing one thing: examples/ /getkern/kern/blob/main/examples . Every read verb also answers in JSON, so nothing has to parse a table: kern ps --json | jq '. | select .health == "unhealthy" | .name' kern volume ls --json ps · images · stats · inspect · builds · pod ls · config list · diff kern speaks docker-compose.yml . Point it at the stack you already have and kern compose up runs it with no daemon and no Docker Desktop, the same on Linux, WSL2 and ARM boards. compose.yaml - a real stack, unchanged services: db: image: postgres:alpine environment: { POSTGRES PASSWORD: secret, POSTGRES DB: app } web: image: adminer ports: "8080:8080" depends on: db kern compose compose.yaml up Both official images start, web reaches db by service name, and the port is published to the host. Warm images cached the web tier serves in ~0.3 s , and the stack costs only what postgres and adminer actually use ~66 MB here with zero daemon on top, where Docker Desktop is a background VM before your first container. Official images that drop to a non-root user postgres, redis, ... want uidmap and a /etc/subuid line, and outbound image pulls want pasta ; both are one apt install on a dev box, and kern doctor names either if it is missing. This is the local dev loop, not a production orchestrator: no Swarm, no overlay networks. Run agent or LLM-generated code from your own program with , a thin, dependency-free wrapper over the kern-sandbox kern binary. Every call runs in a fresh isolated box: network off, memory and pid caps, capabilities dropped, output bounded, and a timeout the binding itself enforces. pip install kern-sandbox PyPI · needs the kern binary above, on PATH or $KERN BIN npm install kern-sandbox npm · same python from kern sandbox import run code r = run code "import platform; print platform.python version " print r.stdout ran in a fresh box; a timeout / OOM / blocked escape is data on r.fault Faults are data, not exceptions : a timeout, OOM-kill or blocked syscall is a field on the result, not a raise. A fresh box per call by default; Sandbox keeps a workspace across calls and a warm kernel keeps one interpreter for sub-millisecond cells weaker isolation, by choice . Rich results without a Jupyter kernel : the last expression, display and matplotlib figures come back captured, like a notebook cell.- Ships an MCP server kern-mcp : a dependency-free stdio server that gives Claude Desktop, Cursor or any MCP client a local code interpreter. Point the client at it: { "mcpServers": { "kern": { "command": "kern-mcp" } } } Tools: run code python/bash/node , write file , read file , list files . Each call is a fresh network-off box; files persist across calls in a workspace on disk. Setup command, image and the other options: bindings/python/README.md /getkern/kern/blob/main/bindings/python/README.md . Full API, Python and Node: bindings/python/README.md /getkern/kern/blob/main/bindings/python/README.md · bindings/node/README.md /getkern/kern/blob/main/bindings/node/README.md . A slice is declared once in ~/.config/kern/kern.toml and attached by name, to a sandboxed box or a bare process, with the same token. Three kinds: vcpu: CPU and memory , vdisk: a size-capped scratch disk and vgpio: device nodes . Two of them, and the anchors they are carved from: cpu the host budget a slice is carved from id = "cpu:0" cores = 8.0 vcpu 1.5 cores and 512 MiB - attach as vcpu:heavy name = "heavy" backend = "cpu:0" cpus = 1.5 memory = "512m" gpio a controller anchor id = "gpio:0" vgpio exactly one device node - attach as vgpio:sensor name = "sensor" backend = "gpio:0" i2c = "/dev/i2c-1" kern validate ~/.config/kern/kern.toml check it before anything runs kern box train --image alpine vcpu:heavy vdisk:scratch -- ./train.sh kern run vcpu:heavy -- ./train.sh the same slice, no sandbox kern box iot --image alpine vgpio:sensor -- ls /dev Profiles compose: several attach to one box, and an explicit flag beats a profile's own value. Every key is spelled like its CLI flag, so cpus is --cpus and memory is --memory . A backend naming no declared pool is refused when the config is read, not when the box runs. docs/RESOURCES.md /getkern/kern/blob/main/docs/RESOURCES.md has the field-by-field schema. A vdisk: is a RAM-backed tmpfs when kern runs rootless, whatever its backend says, and an ext4-on-loop image with a real quota when it runs privileged. kern says which one you got, per profile, rather than letting you assume, and the size cap is enforced either way. vgpio: is chip-granular, not per-line. Asking for pins binds the whole /dev/gpiochipN , and that character device exposes every line of that controller. pins = 17 does not restrict the box to line 17: the kernel has no per-line mount boundary, so the pin list is cooperative metadata rather than a boundary. Naming a device node, as i2c above does, grants that node and nothing else.| kern | Docker | Podman | | |---|---|---|---| | Daemon | no | yes dockerd + containerd | no | | Rootless | yes, always | opt-in | yes | | Cold start, bare box | ~2.3 ms | ~297 ms | ~293 ms | | Cold start, from an OCI image | ~3.5 ms | ~297 ms | ~293 ms | | Stop a service init handles SIGTERM | ~1.9 ms | ~310 ms | ~380 ms | | Resident memory, nothing running | 0 | 154 to 160 MB | 0 | | Footprint | one 1.52 MB binary | daemon stack | multi-binary install | | OCI images, pull / build / push | yes | yes | yes | docker-compose.yml | yes, read as-is | yes | partial | | Overlay networks, Swarm, CRI | no | yes | partial | | GPU | on the roadmap | yes | yes | Intel i7-14700KF, Linux 7.0.0, the release binary, one script you can run yourself: python3 examples/benchmark.py . Yours will differ with your CPU, kernel and filesystem. | kern | bubblewrap | runc | podman | docker | | |---|---|---|---|---|---| | Cold start bare box | ~2.3 ms | ~2.3 ms | ~18.6 ms | ~293 ms | ~297 ms | | 200 boxes in parallel | ~0.11 s | ~0.16 s | ~0.35 s | ~44.8 s | ~16.2 s | Three thousand at once take ~2.2 s, and a live box costs ~0.3 MB of memory. Two honest notes. Nobody wins single-shot latency outright : the floor for unshare + exec is 1 to 2 ms, so the whole top tier sits inside its own noise, and bubblewrap is a launcher with no images, caps or lifecycle. The gap that means something is to the engines , two orders of magnitude above. Method, per-phase breakdown, board numbers and every caveat: BENCHMARKS.md . Namespaces, a pivot root , 16 dangerous capabilities dropped before exec, an always-on seccomp allowlist by default moby's own default filter minus kern's 35 escape syscalls, which stay hard-killed; a syscall outside the vetted set returns ENOSYS , and the wider denylist is the opt-out via KERN SECCOMP=denylist , cgroup v2 limits --require-limits refuses to start unless they bind , and a deny-by-default /dev . Where a boundary is cooperative rather than kernel-enforced, SECURITY.md /getkern/kern/blob/main/SECURITY.md says so and names the bypass. You do not have to take it on trust: pentest/ /getkern/kern/blob/main/pentest holds four adversarial suites that assert those boundaries against the kernel rather than against kern's own reporting, and they run without a registry account or a network. sh pentest/run-with-local-registry.sh ./target/release/kern pentest/pentest-ports.sh Report a vulnerability privately via GitHub Security Advisories or hello@getkern.dev mailto:hello@getkern.dev . | docs/DOCKER-COMPAT.md /getkern/kern/blob/main/docs/DOCKER-COMPAT.md docs/RESOURCES.md /getkern/kern/blob/main/docs/RESOURCES.md · docs/CONFIG.md /getkern/kern/blob/main/docs/CONFIG.md · docs/STORAGE.md /getkern/kern/blob/main/docs/STORAGE.md · docs/EGRESS.md /getkern/kern/blob/main/docs/EGRESS.md kern.toml schema, volumes and egress docs/THREAT MODEL.md /getkern/kern/blob/main/docs/THREAT MODEL.md · SECURITY.md /getkern/kern/blob/main/SECURITY.md · OPEN ITEMS.md /getkern/kern/blob/main/OPEN ITEMS.md BENCHMARKS.md /getkern/kern/blob/main/BENCHMARKS.md · EDGE.md /getkern/kern/blob/main/EDGE.md examples/ /getkern/kern/blob/main/examples · blog/ /getkern/kern/blob/main/blog bindings/python/README.md /getkern/kern/blob/main/bindings/python/README.md · bindings/node/README.md /getkern/kern/blob/main/bindings/node/README.md kern-sandbox SDK: embed kern in Python or Node The core is done. Everything above works today: 840 Rust, 78 Python and 61 Node tests, clippy-clean, cargo-deny -clean, on real hardware: Linux, WSL2, Raspberry Pi 5, Jetson Orin Nano, Arduino UNO Q. v0.7.0 is the first published release. The CLI and config surface can still change, always called out in CHANGELOG.md /getkern/kern/blob/main/CHANGELOG.md . Issues and pull requests are welcome. CONTRIBUTING.md /getkern/kern/blob/main/CONTRIBUTING.md has the workflow and the gates; contributions are covered by the CLA /getkern/kern/blob/main/CLA.md . Alex, @realexhub https://github.com/realexhub . Commits come from @getkerndev https://github.com/getkerndev , the project's commit identity. The commits are not signed; the release TAG is. That is what to verify: git verify-tag v0.7.0 against the key in provenance/ /getkern/kern/blob/main/provenance , whose fingerprint is in SECURITY.md /getkern/kern/blob/main/SECURITY.md . Apache-2.0. See LICENSE /getkern/kern/blob/main/LICENSE and TRADEMARK.md /getkern/kern/blob/main/TRADEMARK.md .