man-pages.7: wfix

[thirdparty/man-pages.git] / man7 / pid_namespaces.7

diff --git a/man7/pid_namespaces.7 b/man7/pid_namespaces.7
index 1f85e6bb4845aa5f928ab32087a77eaf0427ceea..867939b0f3fb76814f6ca4dd1b6cb90714053600 100644 (file)
--- a/man7/pid_namespaces.7
+++ b/man7/pid_namespaces.7
@@ -24,7 +24,7 @@
 .\" %%%LICENSE_END
 .\"
 .\"
-.TH PID_NAMESPACES 7 2017-05-03 "Linux" "Linux Programmer's Manual"
+.TH PID_NAMESPACES 7 2019-03-06 "Linux" "Linux Programmer's Manual"
 .SH NAME
 pid_namespaces \- overview of Linux PID namespaces
 .SH DESCRIPTION
@@ -64,14 +64,9 @@ using the
 .BR CLONE_NEWPID
 flag) has the PID 1, and is the "init" process for the namespace (see
 .BR init (1)).
-A child process that is orphaned within the namespace will be reparented
-to this process rather than
-.BR init (1)
-(unless one of the ancestors of the child
-in the same PID namespace employed the
-.BR prctl (2)
-.B PR_SET_CHILD_SUBREAPER
-command to mark itself as the reaper of orphaned descendant processes).
+This process becomes the parent of any child processes that are orphaned
+because a process that resides in this PID namespace terminated
+(see below for further details).
 .PP
 If the "init" process of a PID namespace terminates,
 the kernel terminates all of the processes in the namespace via a
@@ -83,7 +78,7 @@ In this case, a subsequent
 .BR fork (2)
 into this PID namespace fail with the error
 .BR ENOMEM ;
-it is not possible to create a new processes in a PID namespace whose "init"
+it is not possible to create a new process in a PID namespace whose "init"
 process has terminated.
 Such scenarios can occur when, for example,
 a process uses an open file descriptor for a
@@ -239,6 +234,39 @@ Among other things, this means that the parental relationship
 between processes mirrors the parental relationship between PID namespaces:
 the parent of a process is either in the same namespace
 or resides in the immediate parent PID namespace.
+.PP
+A process may call
+.BR unshare (2)
+with the
+.B CLONE_NEWPID
+flag only once.
+After it has performed this operation, its
+.IR /proc/PID/ns/pid_for_children
+symbolic link will be empty until the first child is created in the namespace.
+.\"
+.\" ============================================================
+.\"
+.SS Adoption of orphaned children
+When a child process becomes orphaned, it is reparented to the "init"
+process in the PID namespace of its parent
+(unless one of the nearer ancestors of the parent employed the
+.BR prctl (2)
+.B PR_SET_CHILD_SUBREAPER
+command to mark itself as the reaper of orphaned descendant processes).
+Note that because of the
+.BR setns (2)
+and
+.BR unshare (2)
+semantics described above, this may be the "init" process in the PID
+namespace that is the
+.I parent
+of the child's PID namespace,
+rather than the "init" process in the child's own PID namespace.
+\" Furthermore, by definition, the parent of the "init" process
+.\" of a PID namespace resides in the parent PID namespace.
+.\"
+.\" ============================================================
+.\"
 .SS Compatibility of CLONE_NEWPID with other CLONE_* flags
 In current versions of Linux,
 .BR CLONE_NEWPID
@@ -370,6 +398,7 @@ See
 .BR proc (5),
 .BR capabilities (7),
 .BR credentials (7),
+.BR mount_namespaces (7),
 .BR namespaces (7),
 .BR user_namespaces (7),
 .BR switch_root (8)