Increasing the size of /dev/shm in RHEL 7 can be a useful trick when you need to allocate more shared memory for your applications. In this article, I will guide you through the steps of increasing /dev/shm, sharing my personal insights and commentary along the way.
Introduction
When working with certain applications or processes, you may encounter limitations on the amount of shared memory that can be allocated. This can be especially problematic when dealing with large datasets or memory-intensive operations. Luckily, RHEL 7 provides a straightforward way to increase the size of /dev/shm, allowing you to allocate more shared memory and overcome these limitations.
Step 1: Checking the Current Size of /dev/shm
Before we begin, it’s a good idea to check the current size of /dev/shm. To do this, open a terminal and run the following command:
$ df -h /dev/shm
This command will display the current size of /dev/shm in a human-readable format.
Step 2: Modifying the /etc/fstab File
To increase the size of /dev/shm, we need to modify the /etc/fstab file. This file contains the configuration information for mounting filesystems during the boot process.
Open the /etc/fstab file with your preferred text editor, such as vi or nano.
$ sudo vi /etc/fstab
Within the /etc/fstab file, you will find a line that looks something like this:
tmpfs /dev/shm tmpfs defaults 0 0
To increase the size of /dev/shm, we need to add the size option to this line. The size option specifies the maximum size of the shared memory segment in bytes.
For example, if you want to increase the size of /dev/shm to 4GB, you would modify the line to look like this:
tmpfs /dev/shm tmpfs defaults,size=4G 0 0
Save and exit the /etc/fstab file.
Step 3: Remounting /dev/shm
Now that we have modified the /etc/fstab file, we need to remount /dev/shm for the changes to take effect.
Run the following command to remount /dev/shm:
$ sudo mount -o remount /dev/shm
This command will remount /dev/shm with the new size specified in the /etc/fstab file.
Step 4: Verifying the New Size of /dev/shm
Once you have remounted /dev/shm, it’s important to verify that the new size has been applied successfully.
Run the following command to check the size of /dev/shm:
$ df -h /dev/shm
You should see the new size reflected in the output of this command.
Conclusion
Increasing the size of /dev/shm in RHEL 7 can be a straightforward process that allows you to allocate more shared memory for your applications. By modifying the /etc/fstab file and remounting /dev/shm, you can overcome limitations on shared memory and enhance the performance of memory-intensive operations. Remember to always verify the new size of /dev/shm to ensure that your changes have been applied successfully.