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Comment by nonrandomstring | Hacker News Reader

Is there a connection to User Mode Linux (UML) from around the same time? Or are these completely unrelated projects? I get that running a kernel in the user space provided by another kernel is not really the same as a proper hypervisor, but have never really dug deep into why and what the various tradeoffs are.

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There is no real connection to UML here. Hardware virtualization (Intel VT, AMD-V) are much faster in practice and also don't require the guest operating system to be heavily modified. So besides as curiosity or test vehicle, approaches like UML are pretty dead.

Thanks.

So, slow as it may be, the win for UML (which seems to still have a heartbeat) is that it can run on uP without any specific virtualisation capabilities, right? If I could run Linux on a Z80/6502 then in theory I could run a virtualised Linux on a Z80/6502.

Yes - plus the original win of UML was also being able to run virtual instances on a kernel without proper virtualization capabilities.

In the early 2000s people used to use UMLs as a hosting platform - they didn't have the same security isolation as a proper VM (or even, necessarily, of a container) though.

How do containers have better security isolation than UML?

When I tinkered with UML I think it was prior to cgroups (2007) [0] so my guess is that escaping the UML instance was easier.

[0] https://en.wikipedia.org/wiki/Cgroups

The “original” UML is/was, I believe, NetBSD running as a “rump kernel” and something that virtualization of the actual kernel does not, directly and on its own, fill the shoes of.

UML is older than NetBSD rump kernels.

I stand corrected.

I want to know what Linux a386 was. Couldn't ever really understand what it did.

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