Never head of Sysbox before. At a first glance, the comparison table in their GitHub repo and on their website[1] has a number of inaccuracies which makes me question the quality of their engineering:
— They claim that their solution has the same isolation level ("4 stars") than gVisor, unlike "standard containers", which are "2 stars" only (with Firecracker and Kubevirt being "5 stars). This is very wrong - as far as I can tell, they use regular Linux namespaces with some light eBPF-based filesystem emulation, while the vast majority of syscalls is still handled by the host kernel. Sorry, but this is still "2 stars" and far away from the isolation guarantees provided by gVisor (fully emulating the kernel in userspace, which is at the same level or even better than Firecracker) and nowhere close to a VM.
— Somehow, regular VMs (Kubevirt) get a "speed" rating of only "2 stars" - worse than gVisor ("3 stars") and Firecracker ("4 stars"), even though they both rely on virtually the same virtualization technology. If anything, gVisor is the slowest but most efficient solution while QEMU maintains some performance advantage over Firecracker[2]. These are basically random scores, it's not a good first impression–if you do a detailed comparison like that, at least do a proper evaluation before giving your own product the best score!
— They claim that "standard containers" cannot run a full OS. This isn't true - while it's typically a bad idea, this works just fine with rootless podman and, more recently, rootless docker. Allowing this is the whole point of user namespaces, after all! Maybe their custom procfs does a better job of pretending to be a VM - but it's simply false that you can't do these things without. You can certainly run a full OS inside Kata/Firecracker, too, I've actually done that.
Nitpicking over rating scales aside, the claim that their solution offers large security improvements over any other solution with user namespaces isn't true and the whole thing seems very marketing-driven. The isolation offered by user namespaces is still very weak and not comparable to gVisor or Firecracker (both in production use by Google/AWS for untrusted workloads!). False marketing is a big red flag, especially for something as critical as a container runtime.
Anyone who wants unprivileged system containers might want to look into rootless docker or podman rather than this.
[1]: https://www.nestybox.com
[2]: https://www.usenix.org/system/files/nsdi20-paper-agache.pdf
— They claim that their solution has the same isolation level ("4 stars") than gVisor, unlike "standard containers", which are "2 stars" only (with Firecracker and Kubevirt being "5 stars). This is very wrong - as far as I can tell, they use regular Linux namespaces with some light eBPF-based filesystem emulation, while the vast majority of syscalls is still handled by the host kernel. Sorry, but this is still "2 stars" and far away from the isolation guarantees provided by gVisor (fully emulating the kernel in userspace, which is at the same level or even better than Firecracker) and nowhere close to a VM.
— Somehow, regular VMs (Kubevirt) get a "speed" rating of only "2 stars" - worse than gVisor ("3 stars") and Firecracker ("4 stars"), even though they both rely on virtually the same virtualization technology. If anything, gVisor is the slowest but most efficient solution while QEMU maintains some performance advantage over Firecracker[2]. These are basically random scores, it's not a good first impression–if you do a detailed comparison like that, at least do a proper evaluation before giving your own product the best score!
— They claim that "standard containers" cannot run a full OS. This isn't true - while it's typically a bad idea, this works just fine with rootless podman and, more recently, rootless docker. Allowing this is the whole point of user namespaces, after all! Maybe their custom procfs does a better job of pretending to be a VM - but it's simply false that you can't do these things without. You can certainly run a full OS inside Kata/Firecracker, too, I've actually done that.
Nitpicking over rating scales aside, the claim that their solution offers large security improvements over any other solution with user namespaces isn't true and the whole thing seems very marketing-driven. The isolation offered by user namespaces is still very weak and not comparable to gVisor or Firecracker (both in production use by Google/AWS for untrusted workloads!). False marketing is a big red flag, especially for something as critical as a container runtime.
Anyone who wants unprivileged system containers might want to look into rootless docker or podman rather than this.
[1]: https://www.nestybox.com
[2]: https://www.usenix.org/system/files/nsdi20-paper-agache.pdf