Facilitate the communication between processes by properly setting the performance parameter, Docker shm-size. We at Bobcares can help you with your Docker shm difficulties with our Docker Hosting Support Service.

What is Docker shm-size?

Docker shm size refers to the amount of shared memory allotted to a docker container. A Docker /dev/shm is a temporary file storage filesystem using RAM for storing files. It also facilitates inter-process communication (IPC). However, it’s optional to have a shared memory device.

The parameter, –shm-size=” ” describes the size of the shared memory device. It is in the format <number><unit
>. The number in this case must be larger than 0. The unit might be b (bytes), k (kilobytes), m (megabytes), or g (gigabytes) and is optional. The system uses bytes if the unit is left out. If we completely ignore the size, the system uses 64m.

How to change Docker shm-size?

The Docker container’s shared memory (shm-size) can be modified to suit our application’s requirements. By default, the shm-size is set to 64 MB, but we can change it to a different value as needed.

1. To begin with, launch an Ubuntu container:

   docker run --rm -it --name ubuntu ubuntu
2. We can confirm the default shm-size with this command:

   docker inspect ubuntu | grep -i shm

   This will output the current shm-size, which is typically set to 64 MB:
3. To change the shm-size, use the –shm-size option when running the container.

   For example, we can set the shm-size to 2 GB as seen here:

   docker run --rm -it --name ubuntu --shm-size=2gb ubuntu
4. Then, confirm that the shm-size has been changed, you can use this command:

   docker inspect ubuntu | grep -i shm

   This should now output the new shm-size of 2 GB:

   “ShmSize”: 2147483648,
5. Additionally, we can verify that the container has a unique /dev/shm by running the following command:

   ls -l /dev/shm

   This will output total 0, indicating that the container has its own separate shared memory space, distinct from the host’s.

In summary, the article explains how to properly set the Docker shm-size parameter to control the amount of shared memory allocated to a container, which is important for applications like databases that rely heavily on shared memory for inter-process communication.

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Conclusion

Resizing the shm size is now possible with the use of the post’s mentioned instructions. Finally, we offered the simple procedures our Tech team used to change the Docker shm-size.