ipcrm

Updated

September 4, 2026

Overview

ipcrm removes System V IPC objects: shared memory segments, semaphore arrays, and message queues. Use after confirming with ipcs that objects are orphaned — never delete resources still owned by live production processes.

Syntax

ipcrm [options]
ipcrm -m id | -M key
ipcrm -q id | -Q key
ipcrm -s id | -S key

Common Options

Option	Description
`-m shmid`	Remove shared memory by ID
`-M key`	Remove shared memory by key
`-q msqid`	Remove message queue by ID
`-Q key`	Remove message queue by key
`-s semid`	Remove semaphore by ID
`-S key`	Remove semaphore by key
`-a`	Remove all (dangerous; some versions / with filters)
`-v`	Verbose

Exact -a behavior varies — read man ipcrm before bulk deletes.

Examples with Explanations

Inspect then remove one segment

ipcs -m
sudo ipcrm -m 98305
ipcs -m

Remove by key

ipcs -m
# note the key column (hex)
sudo ipcrm -M 0x00000000

Message queues / semaphores

ipcs -q
sudo ipcrm -q 12
ipcs -s
sudo ipcrm -s 34

Scripted cleanup of your own leftovers

# example: remove shared memory owned by current user carefully
id -u
ipcs -m -c
# manually select ids, then:
# ipcrm -m ID

Automating bulk ipcrm without filters is risky on multi-app hosts.

After crash lab example

# app crashed without IPC_RMID
ipcs -m -p
# verify no live PID uses it
ps -p <cpid>,<lpid>
sudo ipcrm -m <shmid>

Notes / Pitfalls

Wrong ID → impact on another application (databases!).
Need permission; root can remove almost anything.
Race with process still attaching — prefer graceful app shutdown.
Keys of 0x00000000 may mean IPC_PRIVATE — identify carefully.
Does not remove POSIX shm files in /dev/shm — use rm there if appropriate.

2026-relevant notes

Prefer designs that set IPC_RMID or use POSIX shm with clear lifecycle.
In containers, IPC namespace teardown often cleans objects automatically on exit.
Document any required SysV objects for legacy apps so ops doesn’t “clean” them.

Additional Resources

man ipcrm