How to Install Mono on CentOS 8

Mono is a platform for developing and running cross-platform applications based on the ECMA/ISO Standards. It is a free and open-source implementation of Microsoft’s .NET framework.

This tutorial describes how to install Mono on CentOS 8.

Prerequisites #

The instructions assume that you are logged in as root or user with sudo privileges
.

Installing Mono on CentOS #

The easiest and the recommended way to install Mono on CentOS 8 is to install it from Mono’s repositories. It is a relatively simple process and will only take a few minutes.

1. Start by importing the repository’s GPG key:

   sudo rpm --import 'http://pool.sks-keyservers.net/pks/lookup?op=get&search=0x3fa7e0328081bff6a14da29aa6a19b38d3d831ef'

   On success, no output is produced.

2. Add the Mono repository to your system by running the command below:

   dnf config-manager --add-repo https://download.mono-project.com/repo/centos8-stable.repo

   The output should look something like the following:

   Adding repo from: https://download.mono-project.com/repo/centos8-stable.repo

3. Once the repository is enabled install Mono:

   sudo dnf install mono-complete 

   mono-complete is a meta-package that installs the Mono runtime, development tools, and all libraries.

4. Verify the installation by running the following command that prints the Mono version:

   mono --version

   At the time of writing this article, the latest stable version of Mono is 6.8.0.105:

   Mono JIT compiler version 6.8.0.105 (tarball Tue Feb  4 19:28:42 UTC 2020)
   Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
       TLS:           __thread
       SIGSEGV:       altstack
       Notifications: epoll
       Architecture:  amd64
       Disabled:      none
       Misc:          softdebug 
       Interpreter:   yes
       LLVM:          yes(610)
       Suspend:       hybrid
       GC:            sgen (concurrent by default)

That’s it. You have successfully installed Mono on your CentOS system, and you can start using it.

Getting Started with Mono #

To ensure that everything is set up correctly, we’re going to build a Hello World program that prints the classic “hello world” message.

Open your text editor
and create a file named hello.cs with the following content:

hello.cs

using System;

public class HelloWorld
{
    public static void Main(string[] args)
    {
        Console.WriteLine ("Hello World!");
    }
}

Use the csc compiler to build the program:

csc hello.cs

The command above will create an executable named hello.exe.

Run the program using the command below:

mono hello.exe

The output should look something like this:

Hello, World

If you want to execute the program only by typing its name, you’ll need to set an executable flag
:

chmod +x hello.exe

You can now run the hello.exe file by typing:

./hello.exe

Conclusion #

The latest stable Mono release packages are available for installation from the official Mono package repository.

If you hit a problem or have feedback, leave a comment below.