diff --git a/man7/pid_namespaces.7 b/man7/pid_namespaces.7 index 294bad56b..fb8de55be 100644 --- a/man7/pid_namespaces.7 +++ b/man7/pid_namespaces.7 @@ -79,15 +79,24 @@ This behavior reflects the fact that the "init" process is essential for the correct operation of a PID namespace. In this case, a subsequent .BR fork (2) -into this PID namespace (e.g., from a process that has done a -.BR setns (2) -into the namespace using an open file descriptor for a -.I /proc/[pid]/ns/pid -file corresponding to a process that was in the namespace) -will fail with the error +into this PID namespace will fail with the error .BR ENOMEM ; it is not possible to create a new processes 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 +.I /proc/[pid]/ns/pid +file corresponding to a process that was in a namespace to +.BR setns (2) +into that namespace after the "init" process has terminated. +Another possible scenario can occur after a call to +.BR unshare (2): +if the first child subsequently created by a +.BR fork (2) +terminates, then subsequent calls to +.BR fork (2) +will fail with +.BR ENOMEM . Only signals for which the "init" process has established a signal handler can be sent to the "init" process by other members of the PID namespace.