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What is DKMS and How to Use It?

Ubuntu 11

Dynamic Kernel Module Support, or DKMS for short, is a framework used in Linux systems to have kernel modules whose sources reside outside the kernel source tree. It is a powerful tool that allows Linux to automatically manage and handle kernel module drivers so that they work seamlessly with core kernel updates. In this article, we will delve into what DKMS is, why it is important, and how to use it.

Quick Answer

DKMS, or Dynamic Kernel Module Support, is a framework used in Linux systems to automatically manage and handle kernel module drivers. It allows for seamless integration of kernel modules with core kernel updates, eliminating the need for manual reinstallation. To use DKMS, you need to place the module installation files in a specific directory and create a configuration file called dkms.conf. DKMS simplifies the management of kernel modules and ensures compatibility with the latest kernel updates.

Understanding DKMS

DKMS is an ingenious solution to an issue that has plagued Linux users for years – the problem of installing and updating kernel modules. Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system.

However, whenever the kernel is updated, all these modules need to be recompiled and reinstalled. This is where DKMS comes in. It automatically rebuilds and installs kernel modules when a new kernel is installed. This means that you don’t have to manually reinstall all your modules every time you upgrade your kernel.

How to Use DKMS

To use DKMS, you need to place the module installation files (source code or binary) in the /usr/src/<module_name>-<module_version>/ directory, along with a configuration file called dkms.conf. This file tells DKMS how to build and configure the module.

The dkms.conf File

The dkms.conf file should contain the necessary information such as the build and clean commands, module name, module location, package name, package version, and whether to remake the initrd image after installing the module. Here is an example of a dkms.conf file:

PACKAGE_NAME="module_name"
PACKAGE_VERSION="module_version"
CLEAN="make clean"
MAKE="make KDIR=/lib/modules/${kernelver}/build"
BUILT_MODULE_NAME[0]="module_name"
BUILT_MODULE_LOCATION[0]="."
DEST_MODULE_LOCATION[0]="/kernel/drivers/driver_dir"
AUTOINSTALL="yes"

Installing the Module

Once you have created the dkms.conf file, you can install the module into DKMS by copying the module installation files into the kernel source tree /usr/src/<module_name>-<module_version>/ and then running the following command:

sudo dkms add -m <module_name> -v <module_version>

This command adds the module to DKMS’s list of modules to build for future kernel installations.

Building and Installing the Module

To build and install the module into the current kernel, you can run the following commands:

sudo dkms build -m <module_name> -v <module_version>
sudo dkms install -m <module_name> -v <module_version>

These commands will build the module and copy it into the current kernel module tree.

Conclusion

DKMS is a powerful tool that simplifies the management of kernel modules. It ensures that your modules remain compatible with the latest kernel updates and saves you the hassle of manually reinstalling your modules every time you update your kernel. By placing module installation files in the /usr/src/<module_name>-<module_version>/ directory and creating a dkms.conf file, you can easily build, install, and update modules across kernel versions.

For more detailed information, you can refer to the DKMS man page or the Ubuntu man page. These resources provide comprehensive guides on setting up your favorite kernel module with DKMS.

What is the purpose of DKMS?

DKMS is used to automatically rebuild and install kernel modules when a new kernel is installed, ensuring compatibility between modules and kernel updates.

How does DKMS work?

DKMS works by placing module installation files in the /usr/src/<module_name>-<module_version>/ directory and using a dkms.conf file to provide instructions on how to build and configure the module. DKMS then automatically rebuilds and installs the module when a new kernel is installed.

Where should I place the module installation files for DKMS?

The module installation files should be placed in the /usr/src/<module_name>-<module_version>/ directory.

What should be included in the `dkms.conf` file?

The dkms.conf file should include information such as the build and clean commands, module name, module location, package name, package version, and whether to remake the initrd image after installing the module.

How do I add a module to DKMS?

To add a module to DKMS, you can use the command sudo dkms add -m <module_name> -v <module_version>. This adds the module to DKMS’s list of modules to build for future kernel installations.

How do I build and install a module using DKMS?

To build and install a module into the current kernel, you can use the commands sudo dkms build -m <module_name> -v <module_version> and sudo dkms install -m <module_name> -v <module_version>. These commands will build the module and copy it into the current kernel module tree.

Can I update modules across different kernel versions using DKMS?

Yes, DKMS allows you to easily update modules across different kernel versions. By placing module installation files in the /usr/src/<module_name>-<module_version>/ directory and creating a dkms.conf file, you can ensure compatibility and easily build, install, and update modules.

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