[TUHS] UNIX testing / error injection

[Arnold Robbins via TUHS]

On Tue, Apr 14, 2026, 10:41 PM Adam Koszek via TUHS <tuhs at tuhs.org> wrote:
>
> [ .... ]
>
> After UNIX was already running many program, were any of the complex
> pieces of system code ever developed in the user-space first?
> Filesystems/schedulers/networking are inherently hard to get right, and the
> compile -> boot -> see kernel fail wasn’t ever fun cycle for me, and it had
> to be hell on slow machines..

If I recall correctly, the initial work on the 4.2BSD fast filesystem
was done in user space.  I'm not sure where I read that, but it might
be discussed in the TUHS archives.

Arnold