Operation of the mkdir command with dockerfile - docker

Question

I cannot create a directory with the mkdir command in a container with dockerfile.
My Dockerfile file is simply ;
FROM php:fpm
WORKDIR /var/www/html
VOLUME ./code:/var/www/html
RUN mkdir -p /var/www/html/foo
In this way I created a simple php: fpm container.
and I wrote to create a directory called foo.
docker build -t phpx .
I have built with the above code.
In my docker-compose file as follows.
version: '3'
services:
web:
container_name: phpx
build : .
ports:
- "80:80"
volumes:
- ./code:/var/www/html
later; run the following code and I entered the container kernel.
docker exec -it phpx /bin/bash
but there is no a directory called foo in / var / www / html.
I wonder where I'm doing wrong.
Can you help me?

Answer 1

The reason is that you are mounting a volume from your host to /var/www/html.
Step by step:
RUN mkdir -p /var/www/html/foo creates the foo directory inside the filesystem of your container.
docker-compose.yml ./code:/var/www/html "hides" the content of /var/www/html in the container filesystem behind the contents of ./code on the host filesystem.
So actually, when you exec into your container you see the contents of the ./code directory on the host when you look at /var/www/html.
Fix: Either you remove the volume from your docker-compose.yml or you create the foo-directory on the host before starting the container.
Additional Remark: In your Dockerfile you declare a volume as VOLUME ./code:/var/www/html. This does not work and you should probably remove it. In a Dockerfile you cannot specify a path on your host.
Quoting from docker:
The host directory is declared at container run-time: The host directory (the mountpoint) is, by its nature, host-dependent. This is to preserve image portability. since a given host directory can’t be guaranteed to be available on all hosts. For this reason, you can’t mount a host directory from within the Dockerfile. The VOLUME instruction does not support specifying a host-dir parameter. You must specify the mountpoint when you create or run the container.

Answer 2

I am able to create a directory inside the 'workdir' for docker as follows:
Dockerfile content
COPY src/ /app
COPY logging.conf /app
COPY start.sh /app/
COPY Pipfile /app/
COPY Pipfile.lock /app/
COPY .env /app/
RUN mkdir -p /app/logs
COPY logs/some_log.log /app/logs/
WORKDIR /app
I have not mentioned the volume parameter in my 'docker-compose.yaml' file
So here is what I suggest: Remove the volume parameter from the 'Dockerfile' as correctly pointed by the Fabian Braun.
FROM php:fpm
RUN mkdir -p /var/www/html/foo
WORKDIR /var/www/html
And remove the volume parameter from the docker-compose file. It will work. Additionally, I would like to know how you tested of there is a directory named 'foo'.
Docker-compose file content
version: '3'
services:
web:
build:
context: .
dockerfile: Dockerfile # The name of your docker file
container_name: phpx
ports:
- "80:80"

Answer 3

You can use the SHELL instruction of Dockerfile.
ENV HOME /usr/local
SHELL ["/bin/sh", "-c"]
RUN mkdir $HOME/logs