>From 4b9194026f901c2247150bb3038c41658700f6dd Mon Sep 17 00:00:00 2001 From: Andrey Vagin Date: Thu, 21 Jul 2016 13:58:06 -0700 Subject: [PATCH] namespace.7: descirbe NS_GET_USERNS and NS_GET-PARENT ioctl-s Signed-off-by: Andrey Vagin --- man7/namespaces.7 | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/man7/namespaces.7 b/man7/namespaces.7 index 98ed3e5..207e4a5 100644 --- a/man7/namespaces.7 +++ b/man7/namespaces.7 @@ -149,6 +149,49 @@ even if all processes in the namespace terminate. The file descriptor can be passed to .BR setns (2). +Since Linux 4.X, the following +.BR ioctl (2) +calls are supported for namespace file descriptors. +The correct syntax is: +.PP +.RS +.nf +.IB fd " = ioctl(" ns_fd ", " ioctl_type ");" +.fi +.RE +.PP +where +.I ioctl_type +is one of the following: +.TP +.B NS_GET_USERNS +Returns a file descriptor that refers to an owning user namespace. +.TP +.B NS_GET_PARENT +Returns a file descriptor that refers to a parent namespace. This +.BR ioctl (2) +can be used for pid and user namespaces. For user namespaces, +.B NS_GET_PARENT +and +.B NS_GET_USERNS +have the same meaning. +.PP +In addition to generic +.BR ioctl (2) +errors, the following specific ones can occur: +.PP +.TP +.B EINVAL +.B NS_GET_PARENT +was called for a nonhierarchical namespace. +.TP +.B EPERM +The requested namespace is outside of the current namespace scope. +.TP +.B ENOENT +.IB ns_fd +refers to the init namespace. +.PP In Linux 3.7 and earlier, these files were visible as hard links. Since Linux 3.8, they appear as symbolic links. If two processes are in the same namespace, then the inode numbers of their -- 2.5.5