diff --git a/docs/yml.md b/docs/yml.md
index a9909e816..f8191766a 100644
--- a/docs/yml.md
+++ b/docs/yml.md
@@ -264,6 +264,16 @@ net: "none"
 net: "container:[name or id]"
 net: "host"
 ```
+### pid
+
+```
+pid: "host"
+```
+
+Sets the PID mode to the host PID mode.  This turns on sharing between
+container and the host operating system the PID address space.  Containers
+launched with this flag will be able to access and manipulate other
+containers in the bare-metal machine's namespace and vise-versa.
 
 ### dns