dkms Command Linux: Complete Guide to Dynamic Kernel Module Support

Dynamic Kernel Module Support (DKMS) is a powerful framework that automatically rebuilds kernel modules when you install a new kernel version. The dkms command is essential for managing third-party drivers and kernel modules that aren’t included in the mainline Linux kernel.

What is DKMS?

DKMS stands for Dynamic Kernel Module Support, a framework designed to automatically rebuild kernel modules whenever you upgrade your kernel. This eliminates the need to manually recompile drivers after each kernel update, making system maintenance much more efficient.

Key benefits of DKMS include:

• Automatic module rebuilding on kernel updates
• Version tracking and rollback capabilities
• Simplified third-party driver management
• Consistent module installation across different kernel versions

Installing DKMS

Before using the dkms command, you need to install the DKMS package on your system.

Ubuntu/Debian Systems

sudo apt update
sudo apt install dkms

Red Hat/CentOS/Fedora Systems

# For RHEL/CentOS
sudo yum install dkms

# For Fedora
sudo dnf install dkms

Arch Linux

sudo pacman -S dkms

DKMS Command Syntax

The basic syntax for the dkms command is:

dkms [action] [module/version] [options]

Where:

• action: The operation to perform (add, build, install, remove, etc.)
• module/version: The module name and version
• options: Additional parameters for the specific action

Essential DKMS Commands

1. Adding a Module to DKMS

To add a module to DKMS for management:

sudo dkms add -m module_name -v version_number

Example:

sudo dkms add -m nvidia -v 470.141.03

Expected output:

Creating symlink /var/lib/dkms/nvidia/470.141.03/source ->
                 /usr/src/nvidia-470.141.03
DKMS: add completed.

2. Building a Module

After adding a module, you need to build it for your current kernel:

sudo dkms build -m module_name -v version_number

Example:

sudo dkms build -m nvidia -v 470.141.03

Sample output:

Kernel preparation unnecessary for this kernel. Skipping...
Building module:
cleaning build area...
make -j8 KERNELRELEASE=5.15.0-56-generic...
cleaning build area...
DKMS: build completed.

3. Installing a Module

To install a built module into the kernel:

sudo dkms install -m module_name -v version_number

Example:

sudo dkms install -m nvidia -v 470.141.03

Output example:

nvidia:
Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/5.15.0-56-generic/updates/dkms/
depmod...
DKMS: install completed.

4. Listing DKMS Modules

To view all modules managed by DKMS:

dkms status

Sample output:

nvidia, 470.141.03, 5.15.0-56-generic, x86_64: installed
virtualbox, 6.1.38, 5.15.0-56-generic, x86_64: built
broadcom-wl, 6.30.223.271, 5.15.0-56-generic, x86_64: installed

5. Removing a Module

To uninstall a DKMS module:

sudo dkms remove -m module_name -v version_number --all

Example:

sudo dkms remove -m nvidia -v 470.141.03 --all

Output:

-------- Uninstall Beginning --------
Module: nvidia
Version: 470.141.03
Kernel: 5.15.0-56-generic (x86_64)
-------------------------------------

Status: Before uninstall, this module version was ACTIVE on this kernel.
nvidia:
 - Uninstallation
   - Deleting from: /lib/modules/5.15.0-56-generic/updates/dkms/
 - Original module
   - No original module was found for this module on this kernel.

depmod...
DKMS: uninstall completed.
-------------------------------------
Deleting module version: 470.141.03
completely from the DKMS tree.
-------------------------------------
Done.

Advanced DKMS Operations

Building for Specific Kernels

You can build modules for specific kernel versions:

sudo dkms build -m module_name -v version_number -k kernel_version

Example:

sudo dkms build -m nvidia -v 470.141.03 -k 5.15.0-58-generic

Autoinstall Feature

To automatically install a module for all future kernels:

sudo dkms autoinstall

This command builds and installs all DKMS modules for the current kernel.

Creating Module Archives

You can create binary archives of built modules:

sudo dkms mkbmdeb -m module_name -v version_number

This creates a .deb package (on Debian-based systems) containing the compiled module.

DKMS Configuration Files

DKMS uses configuration files to define how modules should be built. The main configuration file is dkms.conf, typically located in the module’s source directory.

Example dkms.conf:

PACKAGE_NAME="example-driver"
PACKAGE_VERSION="1.0.0"
BUILT_MODULE_NAME[0]="example"
DEST_MODULE_LOCATION[0]="/kernel/drivers/misc"
AUTOINSTALL="yes"

Troubleshooting DKMS Issues

Common Problems and Solutions

Module Build Failures

If a module fails to build, check the build log:

sudo dkms status -v

Look for detailed error messages in:

/var/lib/dkms/module_name/version/build/make.log

Missing Dependencies

Ensure you have the necessary development packages:

# Ubuntu/Debian
sudo apt install build-essential linux-headers-$(uname -r)

# RHEL/CentOS
sudo yum groupinstall "Development Tools"
sudo yum install kernel-devel

Kernel Headers Not Found

Install kernel headers for your current kernel:

# Check current kernel version
uname -r

# Install matching headers
sudo apt install linux-headers-$(uname -r)

Debugging DKMS Operations

Enable verbose output for detailed information:

sudo dkms build -m module_name -v version_number --verbose

DKMS Best Practices

Module Version Management

• Always use specific version numbers when adding modules
• Keep track of module versions for different kernel releases
• Test modules thoroughly before deploying in production

Backup and Recovery

• Create module archives before major system updates
• Keep source code backups for custom modules
• Document module dependencies and configurations

Performance Considerations

• Use parallel compilation when possible (make -j$(nproc))
• Remove unused modules to reduce rebuild times
• Consider using precompiled modules for common drivers

DKMS Integration with Package Managers

Many third-party drivers integrate seamlessly with DKMS through package managers:

Installing NVIDIA Drivers with DKMS

sudo apt install nvidia-driver-470-dkms

This automatically handles DKMS registration and module building.

VirtualBox Integration

sudo apt install virtualbox-dkms

VirtualBox kernel modules are automatically managed through DKMS.

Monitoring DKMS Operations

You can monitor DKMS operations through system logs:

# View DKMS-related log entries
journalctl | grep -i dkms

# Monitor real-time DKMS activities
sudo journalctl -f | grep -i dkms

Security Considerations

When working with DKMS modules:

• Only install modules from trusted sources
• Verify module signatures when available
• Be cautious with modules that require kernel modifications
• Keep modules updated to patch security vulnerabilities

Conclusion

The dkms command is an essential tool for Linux system administrators and users who need to manage kernel modules dynamically. It simplifies the process of maintaining third-party drivers across kernel updates and provides a robust framework for module version control.

By understanding the core DKMS commands and best practices outlined in this guide, you can effectively manage kernel modules, troubleshoot issues, and maintain system stability while keeping your drivers up to date. Whether you’re managing NVIDIA graphics drivers, VirtualBox modules, or custom hardware drivers, DKMS provides the flexibility and automation needed for modern Linux systems.

Remember to always test DKMS operations in a safe environment before applying them to production systems, and maintain proper backups of your module configurations and source code.