> I specifically said NT APIs to differentiate from the Windows APIs. It depends on what you mean by "NT APIs". If you mean the NT API exposed to user-mode (NT

> I specifically said NT APIs to differentiate from the Windows APIs. It depends on what you mean by "NT APIs". If you mean the NT API exposed to user-mode (NT syscalls), no, that is insufficient to implement WSL1 (or anything else like it). If you mean to include kernel-mode-only NT APIs (including undocumented/private APIs which MS doesn't expose to third parties, even new APIs added specifically for WSL1 to consume), then yes that is. > the whole Windows Subsystem concept was neat design Also worth keeping in mind, that WSL1 is not an "environment subsystem" in the sense that Win32 is – or OS/2 and POSIX/etc were. It has a radically different architecture from a classic Windows NT environment subsystem.