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There seems to have been a change recently on ImageMagick which breaks conversion from pdf to png. My investigation let me to the policy.xml file and this line:
<policy domain="coder" rights="none" pattern="PDF" />
which needs to be changed to this
<policy domain="coder" rights="read|write" pattern="PDF" />
(Note: I didn't have this problem before).
I am able to change that on my personal machine but now I need to change it on a docker container configured through a Dockerfile. How can I do that?
I have tried something using environment variables without success. You can see my dockerfile here:
https://github.com/VivianePons/public-notebooks
Thank you for your help
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When i tested into docker container what's goes wrong, i see error from imagemagick about lost fonts. If you use lightweight version of smth images like linux-alpine or smth else, your images cannot have any important tools like your local machine or VM.
There are two ways you can modify a docker image. Through Dockerfiles. Using the command docker container commit. I'll explain both methods, and at the end, I'll also add which use case would be better for the method in context. How to confirm that Docker has been installed successfully?
In any case, you want to publish your images to a Docker registry. They can be published to a cloud-based registry, like the Docker Hub which, by the way, is the default if you don’t explicitly specify the registry. First create a free Docker ID, then login:
Now go to Docker Hub and check the image is there: In Docker Hub with free registration, you can have one private repository, with unlimited public repositories. Otherwise, you may want to run your own Docker registry, which can be done with one command:
This change to your Dockerfile should work
ARG imagemagic_config=/etc/ImageMagick-6/policy.xml
RUN if [ -f $imagemagic_config ] ; then sed -i 's/<policy domain="coder" rights="none" pattern="PDF" \/>/<policy domain="coder" rights="read|write" pattern="PDF" \/>/g' $imagemagic_config ; else echo did not see file $imagemagic_config ; fi
At runtime (docker run), use a bind mounted volume to overwrite the policy.xml inside the container.
A good, straightforward example of doing this can be found in the How to use this image section of the official Nginx image on Docker Hub.
docker run --name some-nginx -v /some/content:/usr/share/nginx/html -d nginx
Here, the -v flag is your bind mount. -v /some/content:/usr/share/nginx/html says "replace /usr/share/nginx/html in the container with the contents of /some/content on my host. The end result for the user -- if /some/content has an index.html or other default home page as determined in the nginx.conf of the container, Nginx will require no configuration changes because the default Nginx configuration is already looking for index.html at that file system location.
NOTE: Bind mounting isn't additive. The directory on the image will be entirely replaced by whats being mounted.
Or at build time (docker build) use COPY in your Dockerfile to bake your updated policy.xml right into the container, no bind mounting required.
COPY ./path/to/policy.xml /path/in/docker/image/policy.xml
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