Verify the version of ubuntu running in a Docker container

Question

I have Docker Toolbox installed on windows 8.1 and I am creating an image based on ubuntu:latest (which should be 16.04). I want to make sure that my application is indeed run on 16.04. Here is my Dockerfile:

FROM ubuntu:latest
MAINTAINER xyz [email protected]
COPY apt.conf /etc/apt/
RUN apt-get -y update 
RUN apt-get -y  install cmake
RUN mkdir /usr/local/
COPY folder /usr/local/
RUN mkdir /usr/local/build
CMD cd /usr/local/build
CMD cmake /usr/local/

Once the image is built, i try to run :

docker run image uname -r

But it always returns with 4.4.12 boot2docker

Now i know that boot2docker is the lightweight linux VM on top of which containers are spun on windows, however shouldn't running the image give me version of ubuntu it's running? How can i verify this?

Answer 1

The uname command is pulling specs from the kernel running on the host. If I enter a Ubuntu container on my Debian host, the uname will answer with a Debian build of the kernel.

To know the version of Ubuntu you are running, do a

$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04.3 LTS"

It's simple variables that are shell script friendly, so you can run

#!/bin/sh

if [ ! -f /etc/lsb-release ]; then
  echo "lsb-release missing, unlikely to be a Ubuntu system"
  exit 1
fi
. /etc/lsb-release
if [ "$DISTRIB_ID" != "Ubuntu" -o "$DISTRIB_RELEASE" != "16.04" ]; then
  echo "Linux install doesn't appear to be Ubuntu 16.04"
  exit 1
fi
...