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Show HN: NSL – WSL for Linux (frostyard.github.io)

1 points by bketelsen ↗ HN
One of the things that Windows really got right is WSL2. I drive an atomic Linux distro for daily use, but wanted a way to develop with multiple different distros with that same WSL UX. NSL is my answer. It is a faithful reproduction of the developer experience, powered by a single VM that hosts one or more systemd-nspawn containers with your development instances. Host file edits and port sharing come along for the ride, just like WSL. Take a look and tell me what you think... It's yet another step in my long journey to keep my host installation free from all the changing and breaking dev dependencies that force a reinstall every few months.

83 comments

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thayne
How does this compare to distrobox?
bketelsen
Distrobox mounts $HOME in the container at $HOME by default. WSL and NSL do not, and that's my preference. This means you can install tools that change your default path, change your dotfiles, etc, without affecting the host. The other obvious difference is that distrobox is powered by podman or docker, while NSL uses a VM that runs systemd-nspawn containers.
NekkoDroid
> WSL and NSL do not, and that's my preference.

To be fair, WSL mounts all your drives under /mnt/ by default, which I would argue isn't any better, arguably even worse.

jm4
I was wondering the same thing. Distrobox mounts $HOME by default, but it’s trivial to give a distrobox its own $HOME.

Can you explain the advantages of systemd-nspawn containers versus podman/docker? I’m not familiar with systemd-nspawn, but I’m a regular user of distrobox and podman.

the_real_cher
IS it LXC containers or docker? Or are you running a custom chroot namespace setup?
smw
He runs a systemd-nspawnd container in a "small vm", so neither really?
bketelsen
none of the above. a single vm started by systemd-vmspawn which then starts one or more containers for your instances using systemd-nspawn. It ends up being fast and lightweight.
the_real_cher
Oh cool thanks for the info!

It's an interesting project.

Are these systemd containers comparable to lxc containers or better maybe?

This could be a really interesting alternative to fully featured LXC containers.

Ubuntu has a similar cli tool you probably know about called multi-pass but it just spins up Ubuntu distros.

The issue I had with multipass was how difficult it was to access and backup files, I guess it was meant for more of a disposable container.

varispeed
The project is cool, but please use human written text.

The website's Claudisms are unbearable.

graemep
This is most useful to people who run Linux as their daily driver so rather than saying its like WSL can you explain what it offers that existing Linux containers do not?

Its also sounds different from WSL which I thought is a VM rather than a container.

> It's yet another step in my long journey to keep my host installation free from all the changing and breaking dev dependencies that force a reinstall every few months.

Something that also require a bit of explanation. What do you do that makes this such a common problem.

bketelsen
WSL2 uses a shared VM that does host integration (networking, shared files, permanent storage for each instance). NSL uses the same model but with Linux native technical implementations.

As for keeping my host clean - it's the developer's curse that always gets me. Install libWhatever3.2-dev because you need it to compile something, then don't realize until next time you open Chrome that it broke your system in some subtle way. There are dozens of ways to solve this like devcontainers, docker, incus, fully separate or remote vms. I like the WSL2 model so I wanted that same UX.

graemep
So a single VM with multiple containers within it? Interesting, but I think you should make it immediately clear on your site. Persistence is not the USP because there are lots of ways that you can get persistent VMs or sandboxes.
kevin_thibedeau
Stick non-distro libs into /usr/local and they can't break anything.
okanat
Hah! One would wish so but they do. `/usr/local` usually has preference over `/usr` and libraries that use a plugin architecture often break when you update but forget to recompile plugins.
rpcope1
So you've just basically reimplemented LXC?
pkulak
Nope. This is a VM, with containers inside. And the containers weren't "re-implemented", it uses existing systemd containers. That's what I was able to learn by skimming the site for 30 seconds. Did you not even do that? And why even be so condescending to someone else's project?
nurettin
LXC is a jail and qemu is an extra layer of emulation. Why pay that extra cost? Just because it serves a wsl image isn't really an answer. How is that worth the extra layer? See, no answers worth reading in your response.
rao-v
I have to say this is nice packaging. It is weirdly not obvious in how nice it is to cleanly use a different “machine” inside your desktop.

I never thought I’d prefer WSL to even my MacBook for working with remote servers and dev but somehow I do.

I of course know the many ways to roll something like this for myself, yes dev containers are better for many things etc. but it’s wierd how good the ergonomics of a WSL like container are.

bketelsen
Thanks for saying so! That's exactly why I wrote this. The UX of wsl2 is just right. There are a lot of other ways to accomplish this, but none touch that same experience.
snapplebobapple
Have you tried mise? It handled most of that for me because dev environment is exactly what is needed per project
rao-v
I use mise inside WSL. It's sort of a terminal into "workspace" for me. Should probably spin an orbstsck or whatever to do thisnon my macbook
lucideer
I'm very curious about this - as a mise user this seems like a redundant extra level of abstraction that I can't figure out the benefits of (& WSL definitely comes with at least some downsides).

From the OP I see:

> my long journey to keep my host installation free from all the changing and breaking dev dependencies that force a reinstall every few months

mise does this 100% for me (assuming we don't count mise itself as one of those dev dependencies). I'm struggling to think of what falls outside of it?

tonymet
i agree. you can quickly import distro images into named WSL VMs (distros) to keep things separated. and you get close-to-native performance (especially by disabling kernel mitigations)
dingaling911
Looks very cool.

Now all you have to do is run NSL under WSL.

0x457
I'm confused why VM + systemd-nspawn? From my understaing WSL 2 runs a single VM + something like systemd-nspawn per "linux installation", but it runs a VM because it needs linux kernel. Why not just do systemd-nspawn if you alread on linux?
pkulak
Way better isolation, is my guess. Plus, you can use a different kernel this way.

I used to poo-poo when people said that containers aren't a _real_ security boundary, at least for personal stuff, and not a multi-tenant server. But I bet even mid-tier LLMs can break out of LXC/Docker/nspawn at this point.

fhn
can they not break out of a VM?
esseph
Yes, and have.

---

"During a test conducted by Trail of Bits researcher Artem Dinaburg, a preview version of GPT 5.6-Cyber was tasked with breaking out of a Debian 12 virtual machine. Initially, the agent exploited a known Linux kernel vulnerability, CVE-2026-53359, by developing its own exploit. After the host was updated, the agent found another pathway through libslirp, chaining a known vulnerability (CVE-2026-9539) with a previously unassigned bug to gain arbitrary host memory access. Even after QEMU and libslirp were updated, the agent analyzed system components and constructed a new escape chain using three zero-day vulnerabilities and one KVM flaw that had not yet reached the distribution kernel.

These findings suggest that general-purpose VMs may not be adequate security boundaries for highly capable AI agents, especially in older systems with delayed security updates. Trail of Bits recommends using specialized isolation systems like Firecracker, restricting VM access, and implementing rapid patching to mitigate these risks."

---

https://www.scworld.com/brief/ai-agent-repeatedly-escapes-vi...

cookiengineer
Can confirm. My abliterated models kept breaking out of qemu VMs due to BIOS implementation quirks in qemu.

I'm using firecracker now with a very defensive systemd-as-separate-non-admin-user seccomp sandbox on top, which seems to hold them off long enough for me to see an agent going rogue and intervening.

Currently I still have hopes that eBPF sandboxing will help, but just a couple days ago my agent discovered a use after free bug in the ebpf kernel-side verifier... so there's that.

bloppe
CVEs for runc are much more frequent than CVEs for KVM. The attack surface area is bigger, and containers were never intended as a security boundary, but rather as a resource management tool.
dathinab
through just from scanning the feature side

> Your files and your account [..]

> Ports and windows on the host

it is quite likely that you can break out even with no linux containers related CVEs. --isolate does seem to fix that somehow but is explicit opt. in and "more painful to use" ... (which creates a UX challenge unlikely to end well from a security POV).

akdev1l
libkrun exists so we can just run containers inside a virtualized environment without special tooling
zenoprax
I was just testing this and it's not clear that it works out of the box. `krun` shows a different kernel than with `crun` but it doesn't reflect the dropped capabilities in the same way. I'm probably holding it wrong but I'm not sure what to look for at the moment.
avadodin
> Plus, you can use a different kernel this way.

Any kernel could be the last to support old nVidia drivers for your $10k card.

okanat
That has to be the host kernel not the guest kernel. Old Nvidia systems without supported kernel drivers often lack IOMMU to forward PCIe memory, too. I wouldn't recommend to use an outdated host kernel with 2026 AI-powered vulnerability scanners.

Windows (10 LTSC or 11 with dTPM) actually works better for old Nvidia systems with WSL. You even get CUDA libraries within WSL and security updates for the next 5 years.

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bee_rider
The name WSL has always struck me as a bit back area (LSW would seem to make more sense, since it is a Linux subsystem for Windows). I guess they mean it as a Windows Subsystem for Linuxing.

Anyway, should this be called LSL or WSLL? Or maybe LSWSL.

dspillett
It is continuing a historic naming "accident", the precedent having been set by Windows Services for UNIX and similar in the 90s/00s.
bityard
The naming is a bit awkward now, but an original design goal of the Windows NT kernel was the ability to host different types of OS "personalities" (userspace, essentially) on top of the Windows kernel, and these are called "subsystems." Win32 is one such subsystem, although there was no need to formally call it "Windows Subsystem for Win32" because everyone understood that it was just Win32 ported to NT.

The NT kernel designers came from VMS, and during development MS made various half-hearted promises that NT would be able to run VMS software as well but never actually followed through. If they had, there would likely have been a Windows Subsystem for VMS.

lukeh
It’s to do with trademark usage as I understand it.
bitwize
It's an issue because Linux is a trademark. Microsoft cannot call something a "Linux something" without infringing a trademark, but they can say something is "for Linux" the same way third-party companies could market e.g., WordPerfect for Windows. Hence Windows Subsystem for Linux, mirroring the old Windows Services for Unix:

https://en.wikipedia.org/wiki/Windows_Services_for_UNIX

It's a subsystem instead of "services" because WSL1 really was an NT subsystem: a "kernel personality" that knows how to interpret Linux system calls just like the DOS and OS/2 subsystems of early NT.

michaelastreiko
Nice flip of the WSL idea the other way — simple interop like this keeps a one-person stack from turning into a VM zoo.
bezko
someone has to ask the question: can you run lsl in wsl?
bita_nidir
I'll give this one a try, thanks for sharing!

FWIW, I'm currently using systemd-nspawn via mkosi: https://github.com/systemd/mkosi

It makes an image and runs it in separate namespace. It can start at bash or init. It's very fast but there seem to be a problem creating an Ubuntu image on Debian and vice versa.

codr1
This is very cool. GG.
teeskay
Just a recommendation that difference between docker container and nsl on homepage is worth it
naman_307
Is the VM layer mostly for host hygiene, or are you also treating the instances as a real security boundary when something untrusted (deps or agent-written code) runs inside?
dathinab
How does it differ from existing tools kinda do exactly same, like e.g. toolbx. (And to a slightly lesser degree flatpack, snap, etc.)?

And what prevented adopting/supporting existing projects, instead of further tool ecosystem fragmentation?

bketelsen
Most of these tools you mention are designed to work best as an overlay to your $HOME. toolbx, distrobox, and to some extent flatpak and snap. NSL is built to give you the "pet" virtual machines with limited integration to the host - you can get to the host filesystem if you want, and you can use the host's Wayland session. I think a better comparison would be using NSL instead of using a remote computer or VM.
senectus1
would really like a NixOS for this. would be interesting to play with and figure out.
Fnoord
'National security letter' for Linux?

I think I'll stick to Nix & Podman.

aj2048
I've wanted a little more isolation than what distrobox can give me for a while now, and I did enjoy WSL when I used Windows. I've also never heard of Frostyard before, and the other repos look pretty interesting as well. Thanks for sharing!
frunklooper
Nobody wants this
ilvez
Exactly opposite, gonna test it out today for a pet project since I can let Claude go haywire inside if it needs to install any deps from systemside. Similar stuff exists, but this seems lightweight enough for experimentation.
bketelsen
I'd love to hear your thoughts on it afterwards, either here or as an issue on GitHub.
ilvez
Gladly (Y)

Will try to give it a spin later.

isityettime
What differentiates this from distrobox?
tonymet
I now prefer WSL over Darwin, especially with agents because I can easily scope disposable "VMs" that have a clean terminal integration.

It's neat seeing this experience come to linux.

Sure you "could" do this with a bunch of tools, but it's the UX that matters.

Creative idea to fix something that nobody thought was broken, but actually was.