move the description of user ns mapping to proper file

They should stay in runtime not config.

Signed-off-by: Gao feng <[email protected]>

Author: gao-feng

config-linux.md

@@ -16,30 +16,6 @@ Valid values are the strings for capabilities defined in [the man page](http://m
     ]
 ```
 
-## User namespace mappings
-
-```json
-    "uidMappings": [
-        {
-            "hostID": 1000,
-            "containerID": 0,
-            "size": 10
-        }
-    ],
-    "gidMappings": [
-        {
-            "hostID": 1000,
-            "containerID": 0,
-            "size": 10
-        }
-    ]
-```
-
-uid/gid mappings describe the user namespace mappings from the host to the container.
-The mappings represent how the bundle `rootfs` expects the user namespace to be setup and the runtime SHOULD NOT modify the permissions on the rootfs to realize the mapping.
-*hostID* is the starting uid/gid on the host to be mapped to *containerID* which is the starting uid/gid in the container and *size* refers to the number of ids to be mapped.
-There is a limit of 5 mappings which is the Linux kernel hard limit.
-
 ## Default Devices and File Systems
 
 The Linux ABI includes both syscalls and several special file paths.

runtime-config-linux.md

@@ -49,6 +49,32 @@ Also, when a path is specified, a runtime MUST assume that the setup for that pa
     ]
 ```
 
+## User namespace mappings
+
+###### Example
+
+```json
+    "uidMappings": [
+        {
+            "hostID": 1000,
+            "containerID": 0,
+            "size": 10
+        }
+    ],
+    "gidMappings": [
+        {
+            "hostID": 1000,
+            "containerID": 0,
+            "size": 10
+        }
+    ]
+```
+
+uid/gid mappings describe the user namespace mappings from the host to the container.
+The mappings represent how the bundle `rootfs` expects the user namespace to be setup and the runtime SHOULD NOT modify the permissions on the rootfs to realize the mapping.
+*hostID* is the starting uid/gid on the host to be mapped to *containerID* which is the starting uid/gid in the container and *size* refers to the number of ids to be mapped.
+There is a limit of 5 mappings which is the Linux kernel hard limit.
+
 ## Devices
 
 `devices` is an array specifying the list of devices to be created in the container.