1	Namespaces compatibility list
2
3This document contains the information about the problems user
4may have when creating tasks living in different namespaces.
5
6Here's the summary. This matrix shows the known problems, that
7occur when tasks share some namespace (the columns) while living
8in different other namespaces (the rows):
9
10	UTS	IPC	VFS	PID	User	Net
11UTS	 X
12IPC		 X	 1
13VFS			 X
14PID		 1	 1	 X
15User		 2	 2		 X
16Net						 X
17
181. Both the IPC and the PID namespaces provide IDs to address
19   object inside the kernel. E.g. semaphore with IPCID or
20   process group with pid.
21
22   In both cases, tasks shouldn't try exposing this ID to some
23   other task living in a different namespace via a shared filesystem
24   or IPC shmem/message. The fact is that this ID is only valid
25   within the namespace it was obtained in and may refer to some
26   other object in another namespace.
27
282. Intentionally, two equal user IDs in different user namespaces
29   should not be equal from the VFS point of view. In other
30   words, user 10 in one user namespace shouldn't have the same
31   access permissions to files, belonging to user 10 in another
32   namespace.
33
34   The same is true for the IPC namespaces being shared - two users
35   from different user namespaces should not access the same IPC objects
36   even having equal UIDs.
37
38   But currently this is not so.
39
40