Hi Andrey,
On 07/21/2016 11:06 PM, Andrew Vagin wrote:
On Thu, Jul 21, 2016 at 04:41:12PM +0200, Michael Kerrisk (man-pages) wrote:
Hi Andrey,
On 07/14/2016 08:20 PM, Andrey Vagin wrote:
<snip>
Could you add here an of the API in detail: what do these FDs refer to,
and how do you use them to solve the use case? And could you you add
that info to the commit messages please.
Hi Michael,
A patch for man-pages is attached. It adds the following text to
namespaces(7).
Since Linux 4.X, the following ioctl(2) calls are supported for names‐
pace file descriptors. The correct syntax is:
fd = ioctl(ns_fd, ioctl_type);
where ioctl_type is one of the following:
NS_GET_USERNS
Returns a file descriptor that refers to an owning user names‐
pace.
NS_GET_PARENT
Returns a file descriptor that refers to a parent namespace.
This ioctl(2) can be used for pid and user namespaces. For user
namespaces, NS_GET_PARENT and NS_GET_USERNS have the same mean‐
ing.
In addition to generic ioctl(2) errors, the following specific ones can
occur:
EINVAL NS_GET_PARENT was called for a nonhierarchical namespace.
EPERM The requested namespace is outside of the current namespace
scope.
ENOENT ns_fd refers to the init namespace.
Thanks for this. But still part of the question remains unanswered.
How do we (in user-space) use the file descriptors to answer any of
the questions that this patch series was designed to solve? (This
info should be in the commit message and the man-pages patch.)
Thanks,
Michael
[1] https://lkml.org/lkml/2016/7/6/158
[2] https://lkml.org/lkml/2016/7/9/101
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx>
Cc: "W. Trevor King" <wking@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
--
2.5.5
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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