Docker : execute commands as a non-root user - docker

Question

Earlier I used to run with the following command :
sudo docker run --pid=host -dit --restart unless-stopped --privileged -v /home/:/home/ --net=host ubuntu:latest bash -c "cd home && wget http://someurl.com/a.js -O /home/a.js && node a.js && tail -F anything"
This command would launch the container having a root user by default. So the wget http://someurl.com/a.js -O /home/a.js command used to work without any issues.
Now I want to get sound from the container. To make sure that the container and the host plays audio simultaneously I used pulseaudio socket otherwise I used to get device busy error as alsa captures the sound card.
Here is the new command I used to accomplish my requirement:
sudo docker run --pid=host -dit --restart unless-stopped --privileged --env PULSE_SERVER=unix:/tmp/pulseaudio.socket --env PULSE_COOKIE=/home/$USER/pulseaudio.cookie --volume /tmp/pulseaudio.socket:/tmp/pulseaudio.socket --volume /home/$USER/pulseaudio.client.conf:/etc/pulse/client.conf --user $(id -u):$(id -g) -v /home/:/home/ --net=host ubuntu:latest bash -c "cd home && wget http://someurl.com/a.js -O /home/a.js && node a.js && tail -F anything"
problem with pulseaudio is that it doesnt work when the user inside docker is a root user hence I have to use --user $(id -u):$(id -g) in the run command.
Now since the user is not root, the wget http://someurl.com/a.js -O /home/a.js command gives permission denied error.
I want this wget command to execute whenever I start my container.
I want to run the container as non-root as well as be able to execute the wget command also.
Is there any workaround for this?

Answer 1

1- Execute docker command with non-root user
If this is your case and don't want to run docker command with root user, follow this link .
create a docker group and add your current user to it.
$ sudo groupadd docker
$ sudo usermod -aG docker $USER
2- Execute commands inside docker! with non-root user
If I'm right you want to use a non-root user inside docker not the root!
The uid given to your user in the docker is related to the root docker images you are using, for example alphine or ubuntu:xenial as mentioned in this article
But you can simple change the user inside docker by changing a little bit as follow in your Dockerfile and add a new user and user it. like this:
RUN adduser -D myuser
USER myuser
ENTRYPOINT [“sleep”]
CMD [“1000”]
then in the docker file, if you gain the /bin/bash and execute id command in it, you will see that the id of user inside docker is changed.
Update:
If you have a ready to use Dockerfile, then create a new Dockerfile, for example it's name is myDocker, and put code below in it:
from myDockerfile
RUN adduser -D myuser
USER myuser
ENTRYPOINT [“sleep”]
CMD [“1000”]
then save this file,and build it:
$ docker build -t myNewDocker .
$ docker run myNewDocker <with your options>

Answer 2

I solved the issue by using a simple chmod 777 command.
First I executed docker run command without the -c flag or the wget command etc
sudo docker run --pid=host -dit --restart unless-stopped --privileged -v /home/:/home/ --net=host ubuntu:latest bash
Once the container was running I entered this container as a root user using this command :
sudo docker exec -it --user="root" bash
Now once inside the container I executed the command chmod 777 /home/a.js
Then I commited a new image with the above changes.
Run the new image with the wget command
sudo docker run --pid=host -dit --restart unless-stopped --privileged -v /home/:/home/ --net=host ubuntunew:latest bash -c "cd home && wget http://someurl.com/a.js -O /home/a.js && node a.js && tail -F anything"
Now the wget works perfectly in non-root mode

Answer 3

Create the docker group.
$ sudo groupadd docker
Add your user to the docker group.
$ sudo usermod -aG docker $USER
Log out and log back in so that your group membership is
re-evaluated.
On Linux, you can also run the following command to
activate the changes to groups:
$ newgrp docker
Verify that you can run docker commands without sudo.
$ docker run hello-world