Over the years, I've deployed myriad servers and services onto local area networks for use at home, for businesses, for clients, and more. I've also had to install such software to either review or use on my home LAN.

Also: How to create a Linux virtual machine with VirtualBox 

There are times when I'm too busy to install an operating system, install the service in question on the OS, and then configure the service to run properly. When I find myself in such a situation, I'll often turn to virtual appliances.

What are virtual appliances?

A virtual appliance is essentially an operating system pre-configured with certain server-based services included for a single purpose. For example, you might want to install the open-source cloud platform Nextcloud, but you don't want to first install an OS, then install the necessary dependencies, create a database, and then install the software.

Why do all of that when you can deploy a virtual appliance that already has Nextcloud installed? All you would have to do is install a simple-to-use app and launch the Nextcloud instance.

Virtual appliances really do make the process that easy.

The difference between a virtual machine and a virtual appliance

This is pretty simple: A virtual machine is an operating system that's installed as a guest on a host running a virtual machine manager. WIth virtual machines, you create a host on the manager, connect a downloaded ISO to the guest, start the guest, install the operating system, reboot, login, and install the software that you need. A virtual appliance, on the other hand, skips most of that because everything is pre-installed for you. 

Also: How to spin up a Linux virtual machine quickly with Boxes

The pros of using a virtual appliance over a virtual machine are:

• Easy deployment: Virtual appliances can be quickly spun up on demand, saving time and effort.
• Simplified management: With all the necessary pieces bundled together, virtual appliances are easier to monitor, update, and maintain.
• Improved security: Virtual appliances run in an isolated environment, with each appliance shielded from one another and from the guest OS.

The cons of using a virtual appliance are:

• Vendor lock-in: This isn't always the case, but some virtual appliances do lock you into a system software stack.
• Monolithic architecture: Virtual appliance code is tightly coupled together, making it difficult to modify or upgrade various components without affecting the entire system.
• Limited customization: Virtual appliances are often limited in terms of configuration options and customizations, whereas using a virtual machine gives you all the customization you need.

What do you need to use virtual appliances?

There are a couple of ways to deploy VirtualAppliances: via a virtual machine manager or the Multipass virtual machine manager. Once upon a time, it was easy to find virtual appliances for managers like VirtualBox, but those files are becoming sparse. The best way now is via the Multipass command line tool, which can be installed on Linux, MacOS (via Homebrew), and Windows (via Linux Subsystem for Windows). 

Don't let the idea of a command line virtual machine manager keep you from using virtual appliances because they aren't that hard to use. Most virtual appliances can be deployed with a single command, so they are quick and easy.

To that end, you'll need Multipass installed. I'll show you how to install Multipass on an Ubuntu-based distribution (it can be installed on any distribution that supports Snap).

Installing multipass

What you'll need: To get all of this up and running, you'll need an instance of Linux and a user with sudo privileges. I'll also offer the commands to install Multipass on MacOS. To install it on Windows, you need to install the Mulitpass installer.

sudo snap install multipass

If you're on a MacOS machine, you have to first install homebrew and then install Multiplass. The commands for installation are:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
brew install --cask multipass

multipass launch appliance:nextcloud

This can take some time because it has to download the appliance. Give it 2-10 minutes (depending on the speed of your network).

multipass list

You should see Nextcloud listed with an IP address.

That's how easy it is to deploy a virtual machine. If you want to know what other appliances are available, you can issue themultipass findcommand to see a full list.

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