Thanks for the feedback; I am one of the developers of Sysbox. Some answers to the above comments:

- Regarding the container isolation, Sysbox uses a combination of Linux user-namespace + partial procfs & sysfs emulation + intercepting some sensitive syscalls in the container (using seccomp-bpf). It's fair to say that gVisor performs better isolation on syscalls, but it's also fair to say that by adding Linux user-ns and procfs & sysfs emulation, Sysbox isolates the container in ways that gVisor does not. This is why we felt it was fair to put Sysbox at a similar isolation rating as gVisor, although if you view it from purely a syscall isolation perspective it's fair to say that gVisor offers better isolation. Also, note that Sysbox is not meant to isolate workloads in multi-tenant environments (for that we think VM-based approaches are better). But in single-tenant environments, Sysbox does void the need for privileged containers in many scenarios because it allows well isolated containers/pods to run system workloads such as Docker and even K8s (which is why it's often used in CI infra).

- Regarding the speed rating, we gave Firecracker a higher speed rating than KubeVirt because while they both use hardware virtualization, the latter run microVMs that are highly optimized and have much less overhead that full VMs that typically run on KubeVirt. While QEMU may be faster than Firecracker in some metrics in a one-instance comparison, when you start running dozens of instances per host, the overhead of the full VM (particularly memory overhead) hurts its performance (which is the reason Firecracker was designed).

- Regarding gVisor performance, we didn't do a full performance comparison vs. KubeVirt, so we may stand corrected if gVisor is in fact slower than KubeVirt when running multiple instances on the same host (would appreciate any more info you may have on such a comparison, we could not find one).

- Regarding the claim that standard containers cannot run a full OS, what the table in the GH repo is indicating is that Sysbox allows you to create unprivileged containers (or pods) that can run system software such as Docker, Kubernetes, k3s, etc. with good isolation and seamlessly (no privileged container, no changes in the software inside the container, and no tricky container entrypoints). To the best of our knowledge, it's not possible to run say Kubernetes inside a regular container unless it's a privileged container with a custom entrypoint. Or inside a Firecracker VM. If you know otherwise, please let us know.

- Regarding "The claim that their solution offers large security improvements over any other solution with user namespaces isn't true". Where do you see that claim? The table explicitly states that there are solutions that provide stronger isolation.

- Regarding "The isolation offered by user namespaces is still very weak and not comparable to gVisor or Firecracker". User namespaces by itself mitigates several recent CVEs for containers, so it's a valuable feature. It may not offer VM-level isolation, but that's not what we are claiming. Furthermore, Sysbox uses the user-ns as a baseline, but adds syscall interception and procfs & sysfs emulation to further harden the isolation.

- "False marketing is a big red flag, especially for something as critical as a container runtime." That's not what we are doing.

- Rootless Docker/Podman are great, but they work at a different level than Sysbox. Sysbox is an enhanced "runc", and while Sysbox itself runs as true root on the host (i.e., Sysbox is not rootless), the containers or pods it creates are well isolated and void the need for privileged containers in many scenarios. This is why several companies use it in production too.