Re: [PATCH] man/man2/move_mount.2: document EINVAL on multiple instances

[Askar Safin <safinaskar@gmail.com>]

Luca Boccassi <luca.boccassi@gmail.com>:
> I don't think so. This was in a mount namespace, so it was not shared,

If it was not shared, then this seems like a bug. Please, say me
reproduction steps, I will try to fix the bug.

If you don't have reproduction steps, then, at very least, say something
like "this happens at line xxx of this big program".

Also, note that "unshare(CLONE_NEWNS)" and "unshare --mount" behave
differently: if you do "unshare(CLONE_NEWNS)", then all shared mounts
continue to be shared. But if you do "unshare --mount", then it
internally does "unshare(CLONE_NEWNS)" and then equivalent of
"mount --make-rprivate", i. e. makes all mounts inside new namespace
private.

> it was a new image, so not shared either, and '/' was not involved at

When you make a new mount under existing shared mount, it becomes shared, too.
(I just checked this.) Also, on systemd, all mounts (not only '/') are shared
by default, I just checked this, too.

-- 
Askar Safin