How to Use the Command 'modinfo' (with Examples)

The modinfo command is a crucial tool in the Linux operating system that is used to extract information about kernel modules. A kernel module is a piece of code that can be added to or removed from the kernel without the need to reboot the system. These modules are essential for extending the capabilities of the kernel, and modinfo provides a way to query their attributes, such as author information, licensing details, and more. This command is particularly useful for system administrators and developers who need to manage and troubleshoot kernel extensions efficiently.

Use Case 1: List all attributes of a kernel module

Code:

modinfo kernel_module

Motivation:

The primary reason for using this command is to gain a comprehensive understanding of a particular kernel module. By listing all its attributes, a user can gather crucial details such as the module’s version, license type, description, and dependencies. This information is often necessary when you need to ensure compatibility with other modules, verify licensing constraints, or simply document the system configuration.

Explanation:

• modinfo: This is the command that initiates the process of querying a kernel module’s information.
• kernel_module: This argument specifies the name of the kernel module you want information about. Replace kernel_module with the actual name of the module.

Example Output:

filename:       /lib/modules/5.4.0-74-generic/kernel/drivers/usb/storage/usb-storage.ko
license:        GPL
description:    USB Mass Storage driver for Linux
author:         Matthew Dharm <mdharm@one-eyed-alien.net>
srcversion:     AB1234567890CDEF
alias:          usb:v*p*d*dc*dsc*dp*ic08isc06ip50in*
depends:        scsi_mod,usbcore
retpoline:      Y
intree:         Y
name:           usb_storage
vermagic:       5.4.0-74-generic SMP mod_unload modversions 

In this output, you can see detailed information about the usb-storage module, including the file path, license, description, and other metadata that provides insights into its usage and dependencies.

Use Case 2: List a specified attribute only

Code:

modinfo -F author|description|license|parm|filename kernel_module

Motivation:

Sometimes, you might only be interested in a specific aspect of a kernel module, such as the author or the license it is distributed under. This use case is particularly useful when you need to quickly verify module details without sifting through all its attributes, saving time and streamlining the information retrieval process.

Explanation:

• modinfo: This retains its function of querying module information.
• -F: This option specifies that you want to filter the output to only include the specified field(s).
• author|description|license|parm|filename: These are placeholder options representing the specific attribute you are interested in. Replace one of these with the desired field such as author to only see the author’s information.
• kernel_module: Just like before, replace this with the actual name of the module you are interested in.

Example Output:

author: Matthew Dharm <mdharm@one-eyed-alien.net>

With this command, if you were only interested in the author of the usb-storage module, the information is presented clearly without any additional details, demonstrating the efficiency of the -F option in retrieving specific attributes.

Conclusion

The modinfo command serves as a powerful tool for gaining knowledge about Linux kernel modules, which are essential components for system operation and extension. By using modinfo, you are equipped with the ability to either view all attributes or focus on specific details of a kernel module, thereby simplifying system management and aiding in the resolution of any compatibility or licensing questions that may arise.