POSIX isn&#x27;t actually about operating systems. POSIX (1003.1) is about source-level compatibility for 2 languages: C99 and shell scripts.<p>If your C programs use only C99+POSIX facilities, and your shell programs use only POSIX features and utilities, and they work on a platform, then that platform is eligible to be POSIX certified.  POSIX doesn&#x27;t care about the kernel or syscalls or anything like that. It cares about libc, libm, libl, and a couple of file paths.