A Comprehensive Guide to Completely Removing OpenCV from Ubuntu Systems

Introduction

OpenCV is a popular open-source library for computer vision tasks, but manual installations or multiple versions on Ubuntu systems can lead to file residues and compilation errors. For instance, users report errors pointing to deleted OpenCV source directories, often due to not executing make uninstall. This article provides a complete solution to thoroughly remove OpenCV, ensuring a clean system state.

Problem Analysis

When OpenCV is compiled from source without using make uninstall, files may remain in system directories such as /usr/local/lib and /usr/local/bin. This causes compilation errors that reference non-existent paths, e.g., errors pointing to /home/anant/opencv/OpenCV-2.3.1/ even after deletion. Version conflicts are common, where installations from different sources like PPAs and manual compilations overwrite files, leading to dependency issues.

Solution Methods

Using the Find Command

The Linux find command can search for and delete all OpenCV-related files. This method is comprehensive but requires caution to avoid removing essential system files. The command traverses the entire filesystem, finding files with "opencv" in their names and interactively prompting for deletion.

sudo find / -name "*opencv*" -exec rm -i {} \;

Using the -i flag adds interactivity, requiring user confirmation for each deletion to minimize risks.

Recompilation and Uninstallation

If the original build directory is available, recompiling OpenCV and running make uninstall can properly clean the installation. This relies on the install manifest generated during installation, but it may not be feasible if the directory is deleted.

cd /path/to/opencv/build
sudo make uninstall

Ensure compilation parameters match the previous setup to generate the correct uninstall script.

Manual Deletion

For cases where the install prefix is known, files can be manually deleted from specific directories. By default, OpenCV installs to /usr/local/, so removing files from /usr/local/bin and /usr/local/lib is common.

sudo rm /usr/local/bin/*opencv*
sudo rm /usr/local/lib/*opencv*

Adjust the path if a different prefix was used during installation.

Code Examples

The following code snippets demonstrate the application of the discussed commands. Note that these require sudo privileges and should be executed after verifying paths to prevent system damage.

# Using find to remove OpenCV files
sudo find / -name "*opencv*" -exec rm -i {} \;

This command may take time on large systems; alternatively, target specific directories:

# Manual removal from common locations
sudo rm -rf /usr/local/include/opencv*
sudo rm -rf /usr/local/lib/*opencv*

Precautions

Before performing deletions, always back up critical data and use interactive commands like rm -i to confirm each action. Incorrect removal can break system functionality. Additionally, check OpenCV dependencies, as removal might affect other packages. Based on user experiences, a complete removal followed by reinstallation from official sources or PPAs can resolve conflicts effectively.

Conclusion

Thoroughly removing OpenCV requires systematic handling of residual files. Methods such as using the find command, recompilation for uninstallation, or manual deletion enable users to clean their systems and avoid version conflicts. After removal, reinstalling OpenCV from reliable sources ensures stable operation, addressing compilation errors and improving system maintenance efficiency.