File Upload by docker container

Question

I have a spring boot app. Docker container has no permission to create a file.

docker file:

FROM openjdk:8-jdk-alpine

VOLUME /tmp

ADD /build/libs/file-upload-service-2.0.0.jar app.jar

ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

Image Build Command:

docker build -t file-upload-service .

Image Run Command:

docker run -d --name file-upload-service -p 9104:9104 file-upload-service:latest

Folder Permissions:

sudo chown -R  root:docker  /home/storage/

sudo chmod -R 777 /home/storage/

When running with java -jar then the application can create the file.

Answer 1

Problem

You're expecting your code inside docker container to locate a file in your host's filesystem. A docker container is fully contained(as the name suggests) runtime environment which has its own filesystem, network etc. You can not directly access host's filesystem from your docker container unless you have some requisite configurations (mounting) in your docker run .. command or the compose file.

Solution

You'll have to mount the volume /home/storage inside docker container to read/write from/to that location from within the container. To do so, after changing the filesystem permissions in your host (which you have already), use following run command to start the container:

docker run -d --name file-upload-service -v /home/storage:/home/storage -p 9104:9104 file-upload-service:latest

-v flag in the above command tells docker to mount /home/storage directory of the host machine (the left side of :) to the /home/storage directory of the container (the right side of :). You can change these directories as per your convenience.