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setns.2, pid_namespaces.7: Elaborate discussion of the PID namespace descendant limitation 

The setns(2) man page already mentions that CLONE_NEWPID may only
be used with descendant namespaces, but this nuance could be
listed in a few more places so it is not missed.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Mike Frysinger 2015-01-02 13:04:42 -05:00 committed by Michael Kerrisk
parent 639dfde82f
commit ba7d7ed976
2 changed files with 16 additions and 1 deletions
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7
man2/setns.2
View File

@ -55,7 +55,7 @@ must refer to a mount namespace.
.TP
.BR CLONE_NEWPID " (since Linux 3.8)"
.I fd
must refer to a PID namespace.
must refer to a descendant PID namespace.
.TP
.BR CLONE_NEWUSER " (since Linux 3.8)"
.I fd
@ -157,6 +157,11 @@ refers to a namespace whose type does not match that specified in
There is problem with reassociating
the thread with the specified namespace.
.TP
.\" See kernel/pid_namespace.c::pidns_install() [kernel 3.18 sources]
.B EINVAL
The caller tried to join an ancestor (parent, grandparent, etc...)
pid namespace.
.TP
.B EINVAL
The caller attempted to join the user namespace
in which it is already a member.

10
man7/pid_namespaces.7
View File

@ -188,6 +188,16 @@ PID namespace from the caller of
Calls to
.BR getppid (2)
for such processes return 0.
While processes may freely descend into children PID namespaces
(e.g. using
.BR setns (2)
with
.BR CLONE_NEWPID ),
they may not move in the other direction.
That is to say, processes may not enter any ancestor namespaces
(parent, grandparent, etc.).
Changing PID namespaces is a one way operation.
.\"
.\" ============================================================
.\"