How to run sudo commands in Docker? - docker

Question

I'm trying to build a docker container containing Sqlite3 and Flask. But Sqlite isn't getting installed because sudo needs a password. How is this problem solved?
The error:
Step 6/19 : RUN sudo apt-get install -y sqlite3
---> Running in 9a9c8f8104a8
sudo: a terminal is required to read the password; either use the -S option to read from standard input or configure an askpass helper
The command '/bin/sh -c sudo apt-get install -y sqlite3' returned a non-zero code: 1
The Dockerfile:
FROM ubuntu:latest
RUN apt-get -y update && apt-get -y install sudo
RUN useradd -m docker && echo "docker:docker" | chpasswd && adduser docker sudo
USER docker
CMD /bin/bash
RUN sudo apt-get install -y sqlite3
RUN mkdir /db
RUN /usr/bin/sqlite3 /db/test.db
CMD /bin/bash
RUN sudo apt-get install -y python
WORKDIR /usr/src/app
ENV FLASK_APP=__init__.py
ENV FLASK_DEBUG=1
ENV FLASK_RUN_HOST=0.0.0.0
ENV FLASK_ENV=development
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
COPY . .
CMD ["flask", "run"]

Answer 1

sudo is not necessary as you can install everything before switching users.
You should think of consistent layers.
Each version of your image should replace only delta parts.
https://docs.docker.com/develop/develop-images/dockerfile_best-practices/
Please find below an example of what you could use instead of the provided dockerfile.
The idea is that you install dependencies and then run some configuration commands.
Be aware that CMD can be replaced at runtime.
docker run myimage <CMD>
# Base image, based on python installed on debian
FROM python:3.9-slim-bullseye
# Arguments used to run the app
ARG user=docker
ARG group=docker
ARG uid=1000
ARG gid=1000
ARG app_home=/usr/src/app
ARG sql_database_directory=/db
ARG sql_database_name=test.db
# Environment variables, user defined
ENV FLASK_APP=__init__.py
ENV FLASK_DEBUG=1
ENV FLASK_RUN_HOST=0.0.0.0
ENV FLASK_ENV=development
# Install sqlite
RUN apt-get update \
&& apt-get install -y sqlite3 \
&& apt-get clean
# Create app user
RUN mkdir -p ${app_home} \
&& chown ${uid}:${gid} ${app_home} \
&& groupadd -g ${gid} ${group} \
&& useradd -d "${app_home}" -u ${uid} -g ${gid} -s /bin/bash ${user}
# Create sql database directory
RUN mkdir -p ${sql_database_directory} \
&& chown ${uid}:${gid} ${sql_database_directory}
# Switch to user defined by arguments
USER ${user}
RUN /usr/bin/sqlite3 ${sql_database_directory}/${sql_database_name}
# Copy & Run application (by default)
WORKDIR ${app_home}
COPY . .
RUN pip install --no-cache-dir --no-warn-script-location -r requirements.txt
CMD ["python", "-m", "flask", "run"]