Can't build Dockerfile -: Not a directory Error using ADD command

Question

I am trying to make a dockerfile for a python/flask webapp and keep running into issues inspite of multiple changes based off what I've read

The Dockerfile I have at present is as follows:

FROM ubuntu:latest

#Update OS
RUN sed -i 's/# \(.*multiverse$\)/\1/g' /etc/apt/sources.list
RUN apt-get update
RUN apt-get -y upgrade

# Install Python
RUN apt-get install -y python-dev python-pip

# Add requirements.txt
ADD requirements.txt /webapp
ADD requirements.txt .

# Install uwsgi Python web server
RUN pip install uwsgi

# Install app requirements
RUN pip install -r requirements.txt

# Create app directory
ADD . /webapp

# Set the default directory for our environment
ENV HOME /webapp
WORKDIR /webapp

# Expose port 8000 for uwsgi
EXPOSE 8000


ENTRYPOINT ["uwsgi", "--http", "127.0.0.1:8000", "--module", "app:app", "--processes", "1", "--threads", "8"]
#ENTRYPOINT ["python"]
CMD ["app.py"]

Attempting to run this Dockerfile with the command sudo docker build -t imgcomparer .

gives the error:

Step 10/15 : ADD . /webapp
Error processing tar file(exit status 1): Error setting up pivot dir: mkdir /var/lib/docker/aufs/mnt/53420471c832e61b7f75ac5fc5268d64b932a4d589a8464c63bf5868f127ff04/webapp/.pivot_root981494252: not a directory

After some research, I discovered that putting a trailing / at the end of the path would work (see this question and this one)

Upon doing that (and the same on the following lines) I have the following in my dockerfile:

# Create app directory
ADD . /webapp/

# Set the default directory for our environment
ENV HOME /webapp/
WORKDIR /webapp/

that gives this error:

Step 10/15 : ADD . /webapp/
stat /var/lib/docker/aufs/mnt/f37b19a8d72d39cbbdfb0bae6359aee499fab0515e2415e251a50d528708bdd3/webapp/: not a directory

Last, I tried removing the problematic line altogether. When I have

# Create app directory
# ADD . /webapp

# Set the default directory for our environment
ENV HOME /webapp
WORKDIR /webapp

The docker file successfully builds! But, unsurprisingly, trying to run it gives an error:

sudo docker run -t imgcomparer

docker: Error response from daemon: oci runtime error: container_linux.go:247: starting container process caused "chdir to cwd (\"/webapp\") set in config.json failed: not a directory"
: Are you trying to mount a directory onto a file (or vice-versa)? Check if the specified host path exists and is the expected type.

Directory Structure is as follows

app.py
image_data.db
README.txt
requirements.txt
Dockerfile
templates
 - index.html
static/
 - image.js
 - main.css
 img/
   - camera.png
 images/
   - empty

Fiat you need to create the webapp directory, something like RUN mkdir /webapp — user2915097
– user2915097, Commented Apr 25, 2017 at 5:26
I put that immediately before the ADD command and it gives the error: mkdir: cannot create directory '/webapp/': File exists — Brian C
– Brian C, Commented Apr 25, 2017 at 5:29
I think the problem is that earlier you are using ADD requirements.txt /webapp, which is probably creating a file called webapp. Therefore, you can't then treat it as a directory — jorgeh
– jorgeh, Commented Apr 25, 2017 at 5:33
BTW, I don't think the python tag applies to this question — jorgeh
– jorgeh, Commented Apr 25, 2017 at 5:34
I added it to before the ADD requirements.txt line and now it builds... but it does not run! I get an error that imgcomparer unable to load configuration from app.py — Brian C
– Brian C, Commented Apr 25, 2017 at 5:39

akoeltringer · Accepted Answer · 2017-04-25 05:40:08Z

2

I believe you have to create the directory before referencing to it:

RUN mkdir /webapp

edit:

(before ADD requirements.txt /webapp)

With

ADD somefile.ext /folder

(without trailing slash to the folder) you reference a file, so you get a file named folder at the root directory, with the contents of somefile.ext in it. Be careful when you need to reference a directory and when a file.

Thus you could also:

ADD requirements.txt /webapp/

Besides: why do you add requirements.txt twice? You should aim for a little steps as possible in a Dockerfile, so you could do:

[...]
RUN apt-get install -y python-dev python-pip && \
    pip install uwsgi
ADD . /webapp/
RUN pip install -r /webapp/requirements.txt
[...]

edited Apr 25, 2017 at 5:40

answered Apr 25, 2017 at 5:25

akoeltringer

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5 Comments

Brian C Over a year ago

Hmmm... That gives

mkdir: cannot create directory '/webapp/': File exists The command '/bin/sh -c mkdir /webapp/' returned a non-zero code: 1

I put it immediately before the ADD line that is giving me trouble.

akoeltringer Over a year ago

Did you put it BEFORE ADD requirements.txt /webapp?

Brian C Over a year ago

Ah! I had it before ADD . /webapp Moving it further back made it properly build.... but (of course) it does not run. I get an error that imgcomparer unable to load configuration from app.py

akoeltringer Over a year ago

I think that has nothing to do with Docker. See for example here: stackoverflow.com/questions/31164127/…

user2915097 Over a year ago

In fact you had to docker build --no-cache . in order to not use the cache and moving that instruction further back invalidated the cache :-)

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