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| .TH IPC_NAMESPACES 7 2019-08-02 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| ipc_namespaces \- overview of Linux IPC namespaces |
| .SH DESCRIPTION |
| IPC namespaces isolate certain IPC resources, |
| namely, System V IPC objects (see |
| .BR sysvipc (7)) |
| and (since Linux 2.6.30) |
| .\" commit 7eafd7c74c3f2e67c27621b987b28397110d643f |
| .\" https://lwn.net/Articles/312232/ |
| POSIX message queues (see |
| .BR mq_overview (7)). |
| The common characteristic of these IPC mechanisms is that IPC |
| objects are identified by mechanisms other than filesystem |
| pathnames. |
| .PP |
| Each IPC namespace has its own set of System V IPC identifiers and |
| its own POSIX message queue filesystem. |
| Objects created in an IPC namespace are visible to all other processes |
| that are members of that namespace, |
| but are not visible to processes in other IPC namespaces. |
| .PP |
| The following |
| .I /proc |
| interfaces are distinct in each IPC namespace: |
| .IP * 3 |
| The POSIX message queue interfaces in |
| .IR /proc/sys/fs/mqueue . |
| .IP * |
| The System V IPC interfaces in |
| .IR /proc/sys/kernel , |
| namely: |
| .IR msgmax , |
| .IR msgmnb , |
| .IR msgmni , |
| .IR sem , |
| .IR shmall , |
| .IR shmmax , |
| .IR shmmni , |
| and |
| .IR shm_rmid_forced . |
| .IP * |
| The System V IPC interfaces in |
| .IR /proc/sysvipc . |
| .PP |
| When an IPC namespace is destroyed |
| (i.e., when the last process that is a member of the namespace terminates), |
| all IPC objects in the namespace are automatically destroyed. |
| .PP |
| Use of IPC namespaces requires a kernel that is configured with the |
| .B CONFIG_IPC_NS |
| option. |
| .SH SEE ALSO |
| .BR nsenter (1), |
| .BR unshare (1), |
| .BR clone (2), |
| .BR setns (2), |
| .BR unshare (2), |
| .BR mq_overview (7), |
| .BR namespaces (7), |
| .BR sysvipc (7) |