adding .net core to docker container with Jenkins - docker

Question

I'm trying to create a dockerfile that will build an image with .net core 2.0 and Jenkins. I'm kind of new to Docker but want to include .net core 2.0 in my container with Jenkins so I don't have to worry about .net core being installed on the target machine and can build .net core apps with Jenkins in my container. Am I missing something here?
it builds fine up until it runs the apt-get update command and I get the following error:
E: Malformed entry 1 in list file /etc/apt/sources.list.d/dotnetdev.list (component)
E: The list of sources could not be read.
I'm using the steps to install on ubuntu at this link:
https://learn.microsoft.com/en-us/dotnet/core/linux-prerequisites?tabs=netcore2x
My Dockerfile looks like this:
FROM jenkins
# Install .NET Core SDK
USER root
RUN mkdir -p /jenkins
WORKDIR /jenkins
ENV DOTNET_CORE_SDK_VERSION 2.0
RUN curl https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor >/jenkins/microsoft.gpg
RUN mv microsoft.gpg /etc/apt/trusted.gpg.d/microsoft.gpg
RUN sh -c 'echo "deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-ubuntu-xenial-prod xenial main" > /etc/apt/sources.list.d/dotnetdev.list'
RUN apt-get update
RUN apt-get install dotnet-sdk-2.0.0

Answer 1

As of this response you can use the following Dockerfile to get .NetCore 2 installed into the Jenkins container. You can obviously take this further and install the needed plugins and additional software as needed. I hope this helps you out!
FROM jenkins/jenkins:lts
# Switch to root to install .NET Core SDK
USER root
# Just for my sanity... Show me this distro information!
RUN uname -a && cat /etc/*release
# Based on instructiions at https://learn.microsoft.com/en-us/dotnet/core/linux-prerequisites?tabs=netcore2x
# Install depency for dotnet core 2.
RUN apt-get update \
&& apt-get install -y --no-install-recommends \
curl libunwind8 gettext apt-transport-https && \
curl https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.gpg && \
mv microsoft.gpg /etc/apt/trusted.gpg.d/microsoft.gpg && \
sh -c 'echo "deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-debian-stretch-prod stretch main" > /etc/apt/sources.list.d/dotnetdev.list' && \
apt-get update
# Install the .Net Core framework, set the path, and show the version of core installed.
RUN apt-get install -y dotnet-sdk-2.0.0 && \
export PATH=$PATH:$HOME/dotnet && \
dotnet --version
# Good idea to switch back to the jenkins user.
USER jenkins

Answer 2

You can run these commands inside the Docker container in order to install .NET Core. They can also be stored in a Dockerfile (as per #Zooly57)
Install the latest .NET Core 2.0:
sudo apt install libunwind8 gettext apt-transport-https
curl -sSL https://dot.net/v1/dotnet-install.sh | bash /dev/stdin --channel 2.0
Or LTS version of .NET Core
sudo apt install libunwind8 gettext apt-transport-https
curl -sSL https://dot.net/v1/dotnet-install.sh | bash /dev/stdin --channel LTS
Contents of the script here:
https://github.com/dotnet/cli/blob/master/scripts/obtain/dotnet-install.sh

Answer 3

Fantastic answer by Dennis, it's exactly what I ended up doing. It was a nice introduction to Docker as well :-)
Here's my Dockerfile for Jenkins 2.249.2 (LTS at the time of writing) on Debian 9 (stretch):
# Extend Jenkins 2.249.2 on Debian 9 (stretch)
FROM jenkins/jenkins:2.249.2-lts
# Switch to root user to install .NET SDK
USER root
# Print kernel and distro info
RUN echo "Distro info:" && uname -a && cat /etc/*release
# Install needed tools and upgrade installed packages
RUN apt-get update \
&& apt-get install -y --no-install-recommends \
curl apt-transport-https software-properties-common \
&& apt-get upgrade -y
# Add Microsoft repository for .NET SDK
RUN curl -sSL https://packages.microsoft.com/keys/microsoft.asc | apt-key add -
RUN apt-add-repository https://packages.microsoft.com/debian/9/prod/
# Install .NET SDK
RUN apt-get update \
&& apt-get install -y dotnet-sdk-3.1
# Switch back to jenkins user
USER jenkins
The dotnet command worked without setting any paths.
I guess when a newer version of Jenkins is released that uses Debian 10, I'll just update the FROM line then the Microsoft repository URL.

Answer 4

I believe you should follow below approach instead:
Develop your asp.net core app and check in to Git(Any source control)
Have a build server which has Jenkins, .Net Core, Docker installed
Configure Jenkins to communicate with Git (webhook/polling - to see if there is a check in)
And configure a Jenkins job which will do the following
Pull the latest from Git,
Restore,
Build,
Publish the asp.net core application,
Create a docker image which has a capability to run the asp.net core app in it
Upload the docker image just created to your Docker Hub
You may not want to do it exactly as mentioned above especially the source control part. But this approach works well.
I have followed this link while I made the above setup.
Hope it helps. Thanks!

Answer 5

For anyone who is struggling with this topic recently, this is what I added to the bottom of my Dockerfile to install the .NET SDK;
USER root
# Install dependencies
RUN apt-get install wget
RUN wget https://packages.microsoft.com/config/ubuntu/18.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
RUN dpkg -i packages-microsoft-prod.deb
RUN rm packages-microsoft-prod.deb
# Install .NET SDK 6.0
RUN apt-get update;
RUN apt-get install -y apt-transport-https
RUN apt-get update
RUN apt-get install -y dotnet-sdk-6.0
RUN dotnet --version
This is based on installing the SDK on Ubuntu 18.04 as this is the version that AKS uses which was perfect for my scenario
https://learn.microsoft.com/en-us/dotnet/core/install/linux-ubuntu#dependencies