man7/ipc_namespaces.7

   1 .\" Copyright (c) 2019 by Michael Kerrisk <mtk.manpages@gmail.com>
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\"
   6 .TH IPC_NAMESPACES 7 2019-08-02 "Linux man-pages (unreleased)"
   7 .SH NAME
   8 ipc_namespaces \- overview of Linux IPC namespaces
   9 .SH DESCRIPTION
  10 IPC namespaces isolate certain IPC resources,
  11 namely, System V IPC objects (see
  12 .BR sysvipc (7))
  13 and (since Linux 2.6.30)
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  15 .\" https://lwn.net/Articles/312232/
  16 POSIX message queues (see
  17 .BR mq_overview (7)).
  18 The common characteristic of these IPC mechanisms is that IPC
  19 objects are identified by mechanisms other than filesystem
  20 pathnames.
  21 .PP
  22 Each IPC namespace has its own set of System V IPC identifiers and
  23 its own POSIX message queue filesystem.
  24 Objects created in an IPC namespace are visible to all other processes
  25 that are members of that namespace,
  26 but are not visible to processes in other IPC namespaces.
  27 .PP
  28 The following
  29 .I /proc
  30 interfaces are distinct in each IPC namespace:
  31 .IP * 3
  32 The POSIX message queue interfaces in
  33 .IR /proc/sys/fs/mqueue .
  34 .IP *
  35 The System V IPC interfaces in
  36 .IR /proc/sys/kernel ,
  37 namely:
  38 .IR msgmax ,
  39 .IR msgmnb  ,
  40 .IR msgmni ,
  41 .IR sem ,
  42 .IR shmall ,
  43 .IR shmmax ,
  44 .IR shmmni ,
  45 and
  46 .IR shm_rmid_forced .
  47 .IP *
  48 The System V IPC interfaces in
  49 .IR /proc/sysvipc .
  50 .PP
  51 When an IPC namespace is destroyed
  52 (i.e., when the last process that is a member of the namespace terminates),
  53 all IPC objects in the namespace are automatically destroyed.
  54 .PP
  55 Use of IPC namespaces requires a kernel that is configured with the
  56 .B CONFIG_IPC_NS
  57 option.
  58 .SH SEE ALSO
  59 .BR nsenter (1),
  60 .BR unshare (1),
  61 .BR clone (2),
  62 .BR setns (2),
  63 .BR unshare (2),
  64 .BR mq_overview (7),
  65 .BR namespaces (7),
  66 .BR sysvipc (7)