How to set up Mono in Amazon Web Services

We want to run Mono in an AWS EC2 Linux instance but the default yum package for Mono is really out of date: soooo out of date that it won't even compile the latest source code (remember that to compile Mono source you need an already functioning, recent version of Mono)!

So we're going to have to build from scratch. Before we start, you will need to:

• Start an EC2 instance of Amazon's version of Linux
• Connect to that instance with an SSH client

This article was pulled together from multiple sources - but Brad's post was particularly useful.

Setting up the Prerequisites

We want the latest version of all build components, plus the Extra Packages For Enterprise Linux for which yum is already configured but which is disabled by default.  So, edit the repository definition to enable the first EPEL entry (which is the run-time) by entering the following commands:

cd /etc/yum.repos.d
sed '0,/^enabled=0/s/enabled=1/' <epel.repo >/tmp/epel.repo
sudo cp /tmp/epel.repo .

Now we can update all repositories to their latest versions:

sudo yum update

And get some build tools that aren't installed by default:

sudo yum install autoconf libtool gettext make automake gcc gcc-c++

Getting the Sources

Install git so that we can download the sources (the git install at time of writing is about 10MB):

sudo yum install git

Make somewhere to download the Mono sources and download them (be cognisant of the size):

mkdir src
cd src
git clone https://github.com/mono/mono

Compiling the Sources

Build the Mono bootstrapper:

cd mono
./autogen.sh --prefix=/usr/local
make get-monolite-latest

Use the bootstrapper to build Mono, then install it:

make EXTERNAL_MCS="${PWD}/mcs/class/lib/monolite/basic.exe"
sudo make install

But that's not enough.  If you were to return to the source tree and make check you would find that one or two of the tests fail - in particular, one around unhandled exceptions in mscorlib.  We can't accept that but at least the newly installed Mono is better than the monolite version.  So let's clean up and compile again: this time with our newly built version as the compiler.

make clean
./autogen.sh --prefix=/usr/local
make
sudo make install

You should make check now if you have time, just to prove that the new version is clean.
If you wish to try out your new toy, copy the text below into a file called HelloWorld.cs:

public class HelloWorld {
    public static void Main() {
        System.Console.WriteLine("Hello World");
    }
}

Then compile and execute, by:

mcs HelloWorld.c
mono HelloWorld.exe