.NET Core Magic: Develop on one OS, run on another
I recently attempted to write a blog post about Angular and .NET Core 2.0 [Note: It will be posted as soon as the .NET Core 2.0 RPMs are released], using my Red Hat Enterprise Linux (RHEL) VM as the operating system. Even though the .NET Core 2.0 bits are not available yet from Red Hat, I gave it a shot by using a daily build. When I tried to run the code, however, I got an error related to the Roslyn compiler. Sometimes, when you play with fire — i.e. a daily build — you get burned.
And that’s when the creative juices, combined with the knowledge of .NET Core’s Self-contained deployment technology (you might also see it referred to as a “Standalone app”) came to the rescue. Since everything was working in Windows, what if I created, debugged and built the application on my Windows 10 machine, but deployed it to my RHEL VM? I don’t have docker for Windows on my PC, so I’d have to use some command line wizardry to pull this off. As it turns out the wizardry was as simple a third-grade magic trick.
Creating the Angular App
Creating the angular app was one command:
dotnet new angular. Boom … Angular app. Granted, it’s just scaffolding and a tiny demo app, but hey … this is about the underlying technology, not the app itself. Sometime in the future… (Dreams of writing a fantastic app using Angular, then remembers his existing technical debt) … yeah, where was I?
Creating the Angular app/scaffolding yields the following, by the way:
Running the Angular App
At this point, all I need to do is restore the dependencies and run the program:
Success! Now I simply open my browser and point it to
localhost:5000 and I have my Angular app. Here’s the browser screenshot:
Wait. What happened? This is supposed to be easy!
Flipping over to the PowerShell session where I launched my app, I found the following error:
Chocolatey to the Rescue
Aha! Angular needs Node.js to be installed. And this brought me to the coolest part of this exercise. On a whim, based on experience and knowing how things are supposed to work, I tried the following command to install Node.js:
choco install nodejs … and it worked!
Up and Running on Windows
I then ran
refreshenv (as chocolatey was kind enough to suggest) to reload my environment variables and PATH settings and tried running
dotnet run again. I refreshed my browser (which was still looking for localhost:5000) and was rewarded with a running app:
Running the Build on RHEL
So after installing Node.js, the app is running. Now I can build it to run on RHEL by using the following command:
dotnet publish -c Release -r rhel.7.2-x64. This creates a DLL in a directory under the project:
Because I have the directory (bin/Release/netcoreapp1.1/rhel.7.2-x64/publish) shared between my Windows 10 host machine and the RHEL VM, I can switch over to the VM and run the DLL.
But it occurs to me: I’ll need Node.js on my RHEL VM as well if I want this to work.
So, hopping over to my RHEL VM, I installed Node.js using the following commands (which I found at the Node.js website):
[Note: I had to log in as super user (su) in order for these commands to work.]
curl --silent --location https://rpm.nodesource.com/setup_8.x | bash - yum -y install nodejs
Now that my RHEL VM has Node.js installed, I should be able to run the DLL that I compiled from within Windows: The application, compiled on my Windows PC, is running on Linux. That is pretty cool.
Exposing the Web Site
But here’s the only problem: It’s using localhost. I need to expose the web server so it can be reached from outside of my VM, i.e. a browser running on my Windows PC. To accomplish this, I can use an environment variable, ASPNETCORE_URLS, as follows:
Now when I run
bin/Release/netcoreapp1.1/rhel.7.2-x64/publish/angular on my Linux VM — remember, the code was compiled on my Windows PC — I have the following:
Finally, I can point my browser to the IP address of the VM and see the Angular website, compiled on Windows, running on RHEL:
To review: In this particular case, the need to install Node.js complicated the issue. In a “Happy Path” scenario, it’s as simple as this:
- Build the code on your Windows PC, targeting RHEL.
- Install (or share) the created DLL on your RHEL system.
- Run the app on your RHEL system.
Hmmm … can this code run in a Linux container now? That’s for my next blog entry.
For additional information and articles on .NET Core visit our .NET Core web page for more on this topic.
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