Using ipcs & ipcrm: Checking active message q's,memory, semaphores

Using ipcs & ipcrm: Checking active message q's,memory, semaphores
How to run IPCS Interprocess Communication Facilities Status on UNIX
How to view currently active message queues, shared memory, and semaphores.
Running IPCRM removes a message queue, semaphore set, or shared memory id.
How to remove a shared memory identifier.

IPCS, the Interprocess Communication Facilities Status is a UNIX Operating System utility used to analyze the status of active interprocess communications facilities.  

The ipcs command lists active IPC services: message queues, shared memory, and semaphores. This information is used to evaluate system resources and to identify the id of the shared memory, message queue, or semaphores targeted for removal.

Issue the ipcs command:
Example Output:

IPC status from running system
T         ID      KEY        MODE        OWNER    GROUP
Message Queues:
q          0   0x4c544952 -Rrw-rw-rw-     root     root
Shared Memory:
m          0   0x5643     --rw-rw-rw-     root     root
m          1   0x5654     --rw-rw-rw-     root     root
m          2   0x4d4e5251 --rw-r--r--     root     root
m          3   0x55315352 --rw-rw-rw-     root     root
Semaphores:
s          1   0x4453314d --ra-------     root     root
s          2   0x55535253 --ra-ra-ra-     root     root
s   28835844   0          --ra-ra-ra-     usr2      rld
s    9306117   0          --ra-ra-ra-     usr1      rld
s  573571078   0          --ra-ra-ra-      usr      rld

The output is broken into 6 categories:

1. T Type of facility: 

• q message queue,
• m shared memory segment,
• s semaphore

2. ID:  The identifier for the facility entry.

3. Key: The key used as an argument msgget(2), semget(2), or shmget(2) to create the facility.

4. Mode: The facility access modes and flags; the mode consists of 11 characters that are interpreted as follows:

The first 2 characters are:
 
The next 9 characters are allocated for permissions:
 
5. Owner: The login name of the owner of the facility entry

6. Group: The group name of the group of the owner of the facility entry

Once the ID has been identified, the segment can be removed with the ipcrm command. to remove an IPC object from the kernel. 

To remove a shared memory identifier
To remove a semaphore

 

Reference to other documentation:

Progress Article(s):

How to find and remove invalid or orphaned Shared Memory using dbipcs and IPCRM.