How to Fix the mkmf.rb Error in Ruby on Rails on Ubuntu 20.04

Struggling with bundle update failures in Ruby on Rails on Ubuntu 20.04? Discover the solution to the `mkmf.rb` error and get your gems installed successfully!
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This video is based on the question https://stackoverflow.com/q/75703201/ asked by the user 'doggie015' ( https://stackoverflow.com/u/21374875/ ) and on the answer https://stackoverflow.com/a/75751834/ provided by the user 'Taryn East' ( https://stackoverflow.com/u/219883/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting Bundle Update Issues in Ruby on Rails on Ubuntu 20.04

If you're running Ruby on Rails on an Ubuntu 20.04 server and having trouble with your bundle update commands, you're not alone. Many developers encounter frustrating errors, particularly involving the mkmf.rb script when attempting to install multiple gems. This often relates to missing development libraries necessary for building native extensions of Ruby gems. In this post, we will help you understand why this occurs and how to resolve the issue effectively.

Understanding the Problem

When you execute a bundle update, Bundler attempts to install and update all the listed gems as specified in your Gemfile. If you encounter errors like the following:

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It's typically a sign that some essential Ruby development packages are not installed on your system. This missing infrastructure can lead to a cascade of errors, preventing necessary gems from compiling and installing correctly.

The Solution: Installing Required Development Libraries

To address the mkmf.rb error, you will need to ensure that the Ruby development headers are installed correctly. Here's how to do that step-by-step:

Step 1: Install Ruby Development Package

Open your terminal.

Run the following command to install the Ruby development package, which includes the necessary header files that are required to build native extensions:

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This command downloads and installs the Ruby development package (or its equivalent, ruby-devel if you're on a different RPM-based system).

Step 2: Retry Bundle Update

After successfully installing the development packages, try running the bundle update command again in your project directory:

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This should help resolve the issues encountered previously.

Additional Considerations

If you encounter errors related to specific gems after resolving the above issue, consider the following:

Clean Gem Cache: If you're still facing issues, you can clear your gem cache:

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Update RubyGems: Sometimes, updating RubyGems can also be beneficial if they were installed via a package manager. Note that this might require uninstalling system-installed RubyGems and reinstalling them manually.

RVM and Other Ruby Managers: If you were trying to switch between Ruby version managers like RVM and rbenv and have run into residual configuration errors (as indicated by the rvm_path error), ensure any previous configurations are completely removed before trying the new setup.

Docker Considerations: Since your setup involves Docker, make sure your Dockerfile includes all necessary commands to install the Ruby development libraries if the Ruby/Rails application is running in a Docker container.

Conclusion

Dealing with Ruby gems and their dependencies on Ubuntu can sometimes be complex, but by following the steps outlined above, you should be able to resolve common installation issues linked with gem native extensions. If you keep encountering problems, consider reaching out to community forums for additional support or documenting the specific error messages for targeted troubleshooting.

With patience and the right tools, you'll have your Ruby on Rails application running smoothly in no time!