Can't build Dockerfile on Ubuntu Server

Question

I'm working on a python project and I get this problem on the Ubuntu Server while working on my local Windows. It stops in the second step, when trying to run mkdir instruction. It seems that I can't run the typical Ubuntu instructions (apt-get clean, apt-get update)

Dockerfile

FROM python:3

RUN mkdir /code
WORKDIR /code
COPY requirements.txt /code/
RUN pip install --upgrade pip==20.0.2 && pip install -r requirements.txt
COPY . /code/

Output error

OCI runtime create failed: container_linux.go:349: starting container process caused "process_linux.go:297: applying cgroup configuration for process caused \"mountpoint for devices not found\"": unknown

Answer 1

Are you able to run the Docker hello-world image? If not, this may indicate a problem with your installation/configuration

$ docker run hello-world

More information about post-installation steps can be found here . Otherwise, first option is to try restarting Docker

$ sudo systemctl restart docker

The Docker daemon must run with root privileges in the background, I have experienced issues before where on a newly-installed machine the updated group permissions for the daemon have not been fully applied. Restarting the daemon, or logging out & in might fix this.

Furthermore, when you declare a WORKDIR inside a Dockerfile that path will automatically be created it if does not already exist. Once you have set your WORKDIR all your paths can and should be relative to it if possible. Knowing this, we can simplify the Dockerfile

FROM python:3

WORKDIR /code
COPY requirements.txt .
RUN pip install --upgrade pip==20.0.2 && pip install -r requirements.txt
COPY . .

That may be enough to solve your issue. In my experience the Docker build tracebacks can be rather vague at times, but it sounds like that particular error could be stemming from a failed attempt to create a directory, either from a permission issue on the host machine or a syntax issue inside the container.

Answer 2

I solved this problem by (re)installing with apt, instead of snap:

sudo snap remove docker
sudo apt install docker-io

Test with (now working):

sudo docker run hello-world