[PATCH] clone.2: Mention that CLONE_PARENT is off-limits for inits

From: Christian Brauner
Date: Wed Nov 20 2019 - 05:45:17 EST

From: Christian Brauner <christian.brauner@xxxxxxxxxx>

The CLONE_PARENT flag cannot but used by init processes. Let's mention
this in the manpages to prevent suprises.

Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
man2/clone.2 | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/man2/clone.2 b/man2/clone.2
index f0f29d6f1..aa98ab79b 100644
--- a/man2/clone.2
+++ b/man2/clone.2
@@ -646,6 +646,13 @@ if
is set, then the parent of the calling process, rather than the
calling process itself, will be signaled.
+The kernel will not allow global init and init processes in pid
+namespaces to use the
+flag. This is done to prevent the creation of multi-rooted process
+trees. It also avoids unreapable zombies in the initial pid
.BR CLONE_PARENT_SETTID " (since Linux 2.5.49)"
Store the child thread ID at the location pointed to by