Using sudo inside non-priviledged docker container not working

Question

I don't want to be root inside a docker container.

But I have to modify some files which belong to root in a script.

I want to use sudo for this.

This is my docker file:

FROM ubuntu:16.04
RUN apt-get update
RUN apt-get install -y curl wget python openssh-server sudo
RUN mkdir /grader
RUN mkdir /grader/week1
RUN mkdir /grader/week1/assignment2
ADD executeGrader.sh /grader/
RUN groupadd -g 1000 coursera
RUN useradd -g 1000 -u 1000 --shell /bin/bash coursera
RUN usermod -a -G sudo coursera
RUN mkdir /home/coursera
RUN chown coursera:coursera /home/coursera
RUN echo "StrictHostKeyChecking no" >> /etc/ssh/ssh_config
RUN echo "coursera ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
RUN chmod 777 /etc/hostname
USER coursera
EXPOSE 8080
EXPOSE 8081
ENTRYPOINT ["/grader/executeGrader.sh"]

executeGrader.sh contains this one:

#!/bin/bash
id
sudo -u root -H bash -c "hostname localhost"

But I get this one :/

>>docker run -h sdfsdfsdf323 -u 1000:1000 -P stackoverflow 
uid=1000(coursera) gid=1000(coursera) groups=1000(coursera)
hostname: you must be root to change the host name

Any ideas?

Answer 1

Thanks for all your support, this one was finally working for me:

export temphostname=`hostname`
sudo su -c "echo 127.0.0.1 $temphostname >> /etc/hosts"