Docker Error: Failed To Compute Cache Key: How to Fix It

Introduction:

Docker Error “Failed To Compute Cache Key” occurs when Docker is unable to calculate a valid cache key for a build process. This issue usually arises due to changes in the build context, such as modified files or configurations, leading to cache inconsistencies during image creation. Resolving this error involves addressing the changes causing the cache discrepancy or using cache control options to mitigate the problem.

1. Understand the Error:

Before we look at how to fix the problem, let’s figure out why this error happens. During the build process, Docker gives the error message “failed to compute cache key” when it can’t find the appropriate files or Dockerfile. This problem is usually caused by the ‘docker build’ command not being run correctly or by wrong file names.

2. Fix the error: “Failed to Compute Cache Key”

To fix the mistake, do the following:

• First, go to Parent Directory.
  Make sure you are in the right parent folder, where the Dockerfile is. You can switch to the parent location by using the ‘cd’ command:

  $ cd /home/rwagh/my-project/parent

  Run the Docker Build command
  Run the ‘docker build’ command while providing the path to the Dockerfile in the child directory:

  $ docker build -f child-dir/Dockerfile

3. Be aware of possible problems:

Sometimes, the first fix may not fix the problem. Here are a few more things you can do to fix the problem:

• a. Look at the file called “.dockerignore”:
  Check the .dockerignore file to make sure it has all of the files that are needed for the build process. The “failed to compute cache key” error could be caused by a .dockerignore file that isn’t full.
• b. Think about Docker environment settings:
  If you run into problems using Docker support in Visual Studio or with Windows as the Docker environment, you might want to run Docker in a Linux environment (WSL). Changing the Docker environment settings to Linux and then running the steps in the terminal will let you do this.

4. Final Steps:

After making the above fixes, run the ‘docker build’ command again as follows:

$ docker build -t containername/tag ProjectFolder/Dockerfile

Conclusion

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