Understanding the 'lsmod' Command (with examples)

The lsmod command in Linux is a vital utility that provides information about the status of the kernel modules currently loaded in the Linux system. Kernel modules are loadable extensions of the operating system’s kernel that provide additional functionality. These modules are versatile and can be loaded and unloaded as needed, allowing a system to adapt dynamically. The lsmod command lists these kernel modules, providing insights into how your system’s kernel is configured and what functionalities are currently active.

Knowing what kernel modules are loaded can help diagnose hardware compatibility issues, improve system performance, or simply give you a better understanding of your system’s capabilities.

Use case 1: List all currently loaded kernel modules

Code:

lsmod

Motivation:

This use case is perhaps the most straightforward and frequently used aspect of the lsmod command. If you’re an administrator, a developer, or even a curious user wanting to get detailed insights into what kernel modules your Linux system is currently using, this command is indispensable. It can inform you instantly about the modules involved in managing various hardware components or software features, which is essential for troubleshooting and system optimization.

Explanation:

The command lsmod is executed without any arguments, which triggers the system to display a list of all the modules that are currently loaded into the Linux kernel. This list is presented in a tabular format with columns detailing the module name, size, and use count, among others. Since lsmod doesn’t require any arguments, it’s a quick and simple operation meant to retrieve a summary-like status of all active modules.

Example Output:

Module                  Size  Used by
nvidia_drm             61440  1
nvidia_modeset       1187840  12 nvidia_drm
nvidia              19726336  569 nvidia_modeset
kvm_intel             253952  0
kvm                   770048  1 kvm_intel
irqbypass              16384  1 kvm
crct10dif_pclmul       16384  0
crc32_pclmul           16384  0
ghash_clmulni_intel    16384  0
...

In the example output, each line corresponds to a different kernel module. The first column lists the module’s name, the second column indicates the size of the module in bytes, and the third column shows how many other modules are using this module. This provides a snapshot of the kernel’s active configurations, helping users understand dependencies and potentially identify modules that might cause system issues or conflicts.

Conclusion:

The lsmod command is an essential tool for anyone working with Linux, providing a clear view into the kernel modules currently in use. By simply executing lsmod, users can obtain detailed insights into the kernel’s active components, aiding in troubleshooting, performance tuning, and system management. Given its simplicity and utility, it’s a command worth mastering for effective system administration.