I'm using this guide to Build a Voice Kit with Amazon Lex and a Raspberry Pi, but I need to use Docker. The problem is that the script that the guide curls and runs requires access to /dev/tty. I can grant access to /dev/tty when running docker containers, but I don't know how to do that when building containers.
My Dockerfile looks like this:
FROM resin/rpi-raspbian
WORKDIR /app
ADD . /app
#The script requires these
RUN apt-get update
RUN apt-get install iputils-ping
#The script has to be run with sudo priviliges but not as root
USER root
ADD /sudoers.txt /etc/sudoers
RUN chmod 440 /etc/sudoers
RUN useradd -ms /bin/bash lex
RUN echo 'lex:test' | chpasswd
RUN curl https://get.pimoroni.com/phatdac | bash
USER lex
EXPOSE 80
#Comment the last RUN command and uncomment this
#CMD curl https://get.pimoroni.com/phatdac | bash
And when I try to build the container with
docker build -t raspi1 .
it crashes on the script, because it can't access /dev/tty.
When running a container, I can use this script to grant access to /dev/tty and /dev/snd
#!/bin/sh
docker run -ti --rm \
-v /dev/snd:/dev/snd \
--privileged \
raspi7
and then try to use the script on the startup with CMD in the Dockerfile. But if I do that, then I need to use the script every time when running and I also need to do RUN on other stuff after the script has finished which would be nice to have on the Dockerfile when building.
TLDR; How to grant privileges to /dev/tty and /dev/snd when building a docker image?
The moby 's issue mentioned by @Greg has been closed.
It is now possible to build images with privileged rights with docker buildx
:
# syntax=docker/dockerfile:1.3-labs
--security=insecure
option to the RUN
commands that require privileged operations: RUN somecommand
becomesRUN --security=insecure somecommand
docker buildx create --driver-opt image=moby/buildkit:master \ --use --name insecure-builder \ --buildkitd-flags '--allow-insecure-entitlement security.insecure' docker buildx use insecure-builder docker buildx build --allow security.insecure...(other build args)... docker buildx rm insecure-builder
However, note that this method has some restrictions so far. A docker-container driver has no access to docker image
( ref ), so all the images referenced by FROM
need to be in a image registry. And for the built image to be visible to docker image
, you may need to add the output
option in the docker buildx build
command.
Docker currently doesn't support exposing devices, or for that matter privileged operations when building.
According to @cpuguy83 what you are doing now - building a portable image without access to the host and completing the configuration when the container is first started - is the right thing to do:
Doing this kind of stuff at first container start is exactly the right way to go. It's a runtime configuration it shouldn't be in the image.
See bountysource .
There is also and old but still open moby 's issue.
Your problem is probably that /dev/snd doesn't exist inside your docker image. When you run your container, you are actually mounting your host OS /dev/snd inside the container so that your script can be run. Take a look at the following:
[INSERT] > cat Dockerfile
FROM resin/rpi-raspbian
RUN ls /dev && ls /dev/tty && ls /dev/snd
[INSERT] > docker build .
Sending build context to Docker daemon 39.94kB
Step 1/2 : FROM resin/rpi-raspbian
---> d008ca006edc
Step 2/2 : RUN ls /dev && ls /dev/tty && ls /dev/snd
---> Running in 0b738007c71c
core
fd
full
mqueue
null
ptmx
pts
random
shm
stderr
stdin
stdout
tty
urandom
zero
/dev/tty
/bin/ls: cannot access /dev/snd: No such file or directory
The command '/bin/sh -c ls /dev && ls /dev/tty && ls /dev/snd' returned a non-zero code: 2
As you can see, /dev/tty exists, and you have access to it. /dev/snd does not exist, and you aren't inside a running container so you can't mount it as a volume (which you are doing when running the container). I would recommend trying to more fully understand what the script you are running is doing, assess whether it needs access to the host machine's /dev/snd, and if so you may only run the script inside the running container as an image doesn't have any concept of a host machine.
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