Docker compose could not open directory permisson denied - django

Question

I am totally a newbie when it comes to Docker. And I am trying to understand it with a dummy project.
I have a django project and my Dockerfile is inside the Django project's root folder. And my docker-compose.yml file is under the top root folder which contains django project folder and other config files.
my docker-compose.yml
version: '3'
services:
db:
image: postgres
container_name: dummy_project_postgres
volumes:
- ./data/db:/var/lib/postgresql/data
event_planner:
build: ./dummy_project
container_name: dummy_project
volumes:
- .:/web
ports:
- "8000:8000"
depends_on:
- db
links:
- db:postgres
and my Dockerfile
FROM python:3
ENV PYTHONUNBUFFERED 1
RUN mkdir /web
WORKDIR /web
ADD requirements.txt /web/
RUN pip install -r requirements.txt
ADD . /web/
I am trying to run the following commands
# stop and remove the existing containers
docker-compose stop
docker-compose rm -f
# up and run the container
docker-compose build
docker-compose up -d
docker-compose exec dummy_project bash
When I do docker-compose up -d, I see this error.
docker-compose up -d
dummy_project_postgres is up-to-date
Starting dummy_project ... done
warning: could not open directory 'data/db/': Permission denied
I know this question asked before, but I didn't quite get the solution I need and I am stuck for hours now.
EDIT: I have all the permissions for all the folders under the top folder
EDIT2: sudo docker-compose up -d also results the same error.

Answer 1

I solved by adding ":z" to end of volume defintion
version: '3'
services:
db:
image: postgres
container_name: dummy_project_postgres
volumes:
- ./data/db:/var/lib/postgresql/data:z
event_planner:
build: ./dummy_project
container_name: dummy_project
volumes:
- .:/web
ports:
- "8000:8000"
depends_on:
- db
links:
- db:postgres
What ":z" means
Labeling systems like SELinux require that proper labels are placed on
volume content mounted into a container. Without a label, the security
system might prevent the processes running inside the container from
using the content. By default, Docker does not change the labels set
by the OS.
To change the label in the container context, you can add either of
two suffixes :z or :Z to the volume mount. These suffixes tell Docker
to relabel file objects on the shared volumes. The z option tells
Docker that two containers share the volume content. As a result,
Docker labels the content with a shared content label. Shared volume
labels allow all containers to read/write content. The Z option tells
Docker to label the content with a private unshared label. Only the
current container can use a private volume.
https://docs.docker.com/engine/reference/commandline/run/#mount-volumes-from-container---volumes-from
what is 'z' flag in docker container's volumes-from option?

Answer 2

You're trying to mount ./data/db in /var/lib/postgresql/data and you're executing docker-compose with a non-privileged user.
So, we can have two possibilities:
Problem with ./data/db permissions.
Problem with /var/lib/postgresql/data
The simpiest solution is execute docker-compose with a privileged user (root), but if you don't want to do that, you can try this:
Give permissions to ./data/db (I see your EDIT that you've already done it).
Give permissions to /var/lib/postgresql/data
How can you give /var/lib/postgresql/data permissions? Read the following lines:
First, note that /var/lib/postgresql/data is auto-generated by postgre
docker, so, you need to define a new Dockerfile which modifies these
permissions. After that, you need also modify docker-compose to use
this new Dockerfile.
./docker-compose.yml
version: '3'
services:
db:
build:
context: ./mypostgres
dockerfile: Dockerfile_mypostgres
container_name: dummy_project_postgres
volumes:
- ./data/db:/var/lib/postgresql/data
event_planner:
build: ./dumy_project
container_name: dummy_project
volumes:
- .:/web
ports:
- "8000:8000"
depends_on:
- db
links:
- db:postgres
./dumy_project/Dockerfile --> Without changes
./mypostgres/Dockerfile_mypostgres
FROM postgres
RUN mkdir -p /var/lib/postgresql/data
RUN chmod -R 777 /var/lib/postresql/data
ENTRYPOINT docker-entrypoint.sh

Answer 3

This solution is for case that your user is not present in docker group.
First check if your user is in docker group:
grep 'docker' /etc/group
Add user to docker group:
If the command return is empty, then create docker group:
sudo groupadd docker
Else if your user is not present in command return then add him to the group:
sudo usermod -aG docker $USER
Reboot your system
Test it again:
docker run hello-world
Tip: Remember to have the docker service started
If it works, try your docker-compose command again.