Post-Installation Checklist

This page outlines steps that may be required to configure ddcutil after it has been installed.

Kernel Module i2c-dev

ddcutil requires kernel module i2c-dev. If it is not built into your kernel, it must be loaded explicly. To do so, add a file into directory /etc/modules-load.d with the single line:

i2c-dev

As of release 1.4, ddcutil installation should automatically install this file, making manual configuration unnecessary.

For details, see Kernel Module Configuration.

I2C Device Permissions

Permissions must be granted in order for users other than root to run ddcutil.

As of release 2.0, ddcutil installation automatically installs files /usr/lib/udev/rules.d/60-ddcutil-i2c.rules and /usr/lib/udev/rules.d/60-usb.rules.
Using tag uaccess, these rules grant the logged on user read/write access to /dev/i2c devices associated with monitors.

For releases prior to 2.0, or if installing on a system that does not support udev (i.e. does not run systemd), manual configuration may be required. For details, see I2C Device Permissions.

Proprietary Nvidia Driver

The proprietary Nvidia video driver sometimes requires special settings for I2C communication. See Special Nvidia Driver Settings.

Configuration Diagnostics

If ddcutil installs successfully but execution fails, command ddcutil environment can be used to probe the I2C environment and may provide clues as to the problem. For USB connected monitors, use command ddcutil usbenvironment. See Secondary Commands.

Linux command i2cdetect (found in required package i2ctools) provides an independent check of whether the DDC slave address (X37) is active on an I2C bus.

Shared Library Configuration

When installing from source, additional configuration may be required to use shared library libddcutil if it is installed under /usr/local. See Shared Library Configuration. Note that libddcutil is NOT required to run ddcutil.