Re A<p>You did notice how I went from an extremely hard task (full POSIX) to a series of them that gradually deliver more and more useful functionality over time if resources and labor permit? First goal is a runtime. Next is key POSIX features (80&#x2F;20 rule). Next is full POSIX. If you cant do a runtime, you cant do POSIX.<p>Re B<p>Linux kernel is a user-mode API that gets you lefacy apps inmediately. You gradually replace the syscalls with your own and eventually get off it. Meanwhile, critical stuff runs outside Linux VM on a Rust runtime directly on microkernel or other trusted components. WAY better than just Linux kernel.<p>Re C<p>No, there are dozens of projects trying to make OS&#x27;S or runtimes in safe languages. There&#x27;s closer to 100 that started as learning projects then petered out when hard reality set in. Dead link after dead link. Hence, I said it in plural as my recommendation and gradual progression applies to most. Including a Rust project.<p>Re D<p>Im not a Rust user so that&#x27;s new to me. Good to know they have it. Thanks for tip.<p>Re E<p>You addressed that point in isolation. The context is a series of steps with gradual increase of difficulty and intermediate deliverables. Starting at Step 5 is clearly not my recommendation.<p>Re F<p>And Step 6 follows Step 5 if author had skill and resources to achieve it. Starting at Step 6, like 5, dramatically increases odds it will be another entry in archive.org rathet than protecting real systems.<p>More to point, I can name many systems that tool my route to success even on a budget and some resisting NSA pentesting w&#x2F; source. Maybe it&#x27;s ny broken memory but I can&#x27;t name <i>even one</i> project that implemented POSIX in a safe language clean slate. Hence, my recommendation.