Introduction
When dockerizing a Laravel application, is it common to find errors related to permissions and the lack of an application key. At least that happened to me the first time I did it, and I know it is common because, if it is not mentioned in the documentation, then it is not obvious and can happen to many people. In this brief article, we'll see how to fix it.
Key generation
Laravel uses an application key that is placed in an APP_KEY environment variable for anything to do with encryption, as stated in the documentation. This is done by default after installing Laravel, but for some reason it wouldn't occur automatically when using my application's Docker image. Therefore, it is necessary to generate it manually through the following command:
php artisan key:generate
This way, it will be set automatically in the APP_KEY variable of our .env file.
Setting permissions
When using a PHP Docker image that in turn uses PHP-FPM, the www-data user and group are provided. Because of this, it is necessary that this user has the required permissions to create files, for example for logs or files that are stored in a Docker volume connected to the Laravel public folder. Assuming that the working directory of our application's Docker image is /var/www, we need to assign the owner by using the following command:
chown -R www-data:www-data /var/www
Entrypoint file for the Docker image
To simplify this process, a file that acts as entrypoint can be placed in the Docker image, so that when the image is mounted in the container, this file is executed. To do this, we create a file /bin/docker-entrypoint.sh in our project that will work as entrypoint, then, we have to copy this file in the Dockerfile to the filesystem of the container, make it executable and specify that it will be the entrypoint. The above would look like this at the end of the Dockerfile:
# Copy the entrypoint file to the working directory
COPY /bin/docker-entrypoint.sh /usr/local/bin/
# Make the file executable
RUN chmod +x /usr/local/bin/docker-entrypoint.sh
# Set the entrypoint of the container
ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
The content of this file will be the key generation, the configuration of permissions, and the creation of a link between the storage and the public folders (another common mistake, but the title couldn't be that long, right?).
#!/bin/sh
# Set permissions
chown -R www-data:www-data /var/www
# Link storage and public folders
php artisan storage:link
# Generate application key (--force is needed in production to bypass the confirmation)
php artisan key:generate --force
# Execute the specified command in the Dockerfile (CMD ["command"])
exec "$@"
Conclusion
While these types of errors may seem obvious to more experienced people, to people just starting out in the world of Docker or Laravel they are not. Using a file for the container entrypoint provides a great deal of flexibility and power because all the commands we need when running the container can be placed there, so I strongly recommend to use it when needed.
I hope this helps you in case your application doesn't work properly due to any of these problems. If you have questions or want to share something, leave it in the comments :)