Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Docker’s “shared memory namespace” is its IPC namespace: it controls which processes can see System V shared-memory segments, semaphores, and message queues. Use Docker’s --ipc setting to keep a container isolated, let selected containers share IPC, or join the host’s IPC namespace. This is separate from the capacity of /dev/shm, which Docker documents as 64 MiB by default.
What a Docker IPC namespace controls
Linux IPC namespaces isolate interprocess communication resources, including System V shared-memory identifiers, semaphores, and message queues. Processes in separate IPC namespaces do not see one another’s IPC resources. See the Linux IPC namespaces documentation.
In Docker, --ipc selects the IPC namespace a container uses. It answers who can see and use these IPC objects; it does not by itself specify how much shared-memory capacity is available.
Docker IPC modes compared
Docker’s CLI reference describes these --ipc choices. The empty/default choice is not a universal fixed mode: Docker says it depends on daemon version and configuration.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
#1 Best Overall
| Setting | Who shares IPC objects | Host IPC exposed? | Container-to-container use |
|---|---|---|---|
private |
The container uses its own IPC namespace. | No. | No sharing with other containers through this setting. |
shareable |
The container uses its own private IPC namespace, which other containers can join. | No. | Use as the namespace for a selected group of containers. |
container:<name-or-ID> |
The container joins the named or identified container’s IPC namespace. | No, unless that namespace itself is host IPC. | Yes; pair with a shareable donor container. |
host |
The container uses the host system’s IPC namespace. | Yes. | Not limited to a selected donor-and-peer group. |
none |
The container has a private IPC namespace. | No. | No; Docker also does not mount /dev/shm in this mode. |
| Empty or omitted | Uses the daemon default, which Docker says can be private or shareable depending on daemon version and configuration. | Depends on the daemon’s configured default. | Depends on the daemon default. |
These mode definitions are in the Docker container run reference. In particular, none is not just another name for ordinary private IPC: its /dev/shm mount behavior differs.
Share IPC between selected containers
For an application split across containers that needs common IPC mechanisms, Docker documents a shareable donor container and peer containers that join it with container:<donor-name-or-ID>. The donor creates the IPC namespace; peers join that namespace rather than each receiving an independent one.
-
Start the donor with
--ipc=shareable, for example:docker run -d --name ipc-donor --ipc=shareable IMAGE. -
Start a peer with
--ipc=container:ipc-donor, for example:docker run --rm --ipc=container:ipc-donor PEER_IMAGE.Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy. -
Configure the application processes to use the appropriate IPC mechanism, then verify their behavior in your deployment. The namespace setting makes IPC resources visible across the joined containers; it does not configure the application’s own IPC protocol.
The exact commands beyond the documented mode pattern are illustrative; replace image names and arguments with those required by your application. Consult Docker’s CLI reference for the option syntax and supported behavior.
What --ipc=host means
--ipc=host joins the host system’s IPC namespace. That is a broader sharing boundary than selecting one donor container and having only designated peers join its namespace: the container uses the host IPC namespace rather than an IPC namespace private to that container group.
Docker also states that IPC sysctls cannot be used with host IPC: “If you use the –ipc=host option these sysctls are not allowed.” This restriction is documented in the Docker container run reference.
Best Value
- Docker, Docker Swarm, Docker Compose, Programmer, Developer, Coding, Programming, Software Engineer, Code, DevOps, Deploy, Deployment, Kubernetes, Salt, Puppet, Chef, Terraform, Container, AWS, Azure, Cloud, Geek, Funny, Computer, Software, Tech, IT
- Integration, Scrum, Compile, Compilation, Science, Bug, Debug, Python, Linux, Java, Javascript, Scala, Dotnet, Kotlin
- Lightweight, Classic fit, Double-needle sleeve and bottom hem
IPC namespace versus /dev/shm size
Namespace selection and shared-memory capacity are distinct settings. The namespace determines which IPC objects processes can see. The size of /dev/shm concerns available shared-memory storage. Docker’s current daemon reference documents a default container shared-memory size of 64 MiB; it does not establish that changing IPC mode increases that capacity. See the Docker daemon reference.
Consequently, an application’s shared-memory error does not, by itself, establish that it needs host IPC. The Docker references cited here describe namespace modes and the documented size default, but do not diagnose a particular application failure. Check whether the application needs to share IPC objects with another container, and separately check its shared-memory capacity requirements and the applicable Docker configuration.
Quick Recap
Choosing a mode
- Choose private when the container should have its own IPC namespace.
- Choose shareable plus container: when a defined set of containers must use the same IPC namespace.
- Choose host only when the application specifically needs the host IPC namespace and you accept that wider sharing boundary.
- Do not treat none as ordinary private IPC: Docker documents that
/dev/shmis not mounted in none mode. - Check the daemon’s default rather than assuming omitted
--ipcalways means private or always means shareable.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
