My purpose is to run a Linux VM while benefiting from the advanced features of APFS, such as CoW, rather than using a raw disk image (sparse file). If there’s a simpler way to achieve this goal, then this question becomes unnecessary.

I checked the permissions of the same file using different users within the same Linux client: [root@fedora ~]# id uid=0(root) gid=0(root) groups=0(root) [root@fedora ~]# ls -n /TEST -rw-r--r-- 1 0 0 0 Apr 3 2025 /TEST [me@fedora ~]$ id uid=1000(me) gid=10(wheel) groups=10(wheel) [me@fedora ~]$ ls -n /TEST -rw-r--r-- 1 1000 10 0 Apr 3 2025 /TEST This seems to suggest a disturbing fact: the VirtioFS implementation by Apple completely ignores file permissions, with no permission mapping mechanism in place, because it simply doesn’t exist.

Are you saying that this was a deliberate decision, not a mistake, that Apple provides VirtioFS support in a surprising way? You mount virtiofs on Linux, then perform a chown on any file, and it succeeds, but when you check the owner again, nothing has changed because, in fact, it’s a no-op. And Apple thinks this is correct, intuitive, and doesn’t require documentation?

Technically, this problem can be solved, such as the unprivileged mode of virtiofsd, which uses user_namespaces, but it’s unlikely that Apple will provide this feature within a limited timeframe.