A Complete Guide to Downgrading Node.js on Ubuntu

As a full-stack developer, there are many scenarios where downgrading to an older Node.js version is necessary – testing compatibility issues, comparing performance across versions, and mimicking production environments. Thankfully, Node.js makes downgrading incredibly simple by leveraging node version manager tools like nvm.

In this comprehensive 2600+ word guide, we will cover:

• The benefits and common use cases of downgrading Node.js
• An overview of Node.js release cycle and versioning scheme
• A detailed walkthrough of downgrading Node.js on Ubuntu 20.04 with nvm
• Best practices when managing multiple Node.js versions
• Alternative downgrading options
• Troubleshooting advice
• And more…

So let‘s get started!

Why Downgrade Node.js?

Before we dive into the step-by-step downgrading process, it‘s important we first understand the motivations and use cases that require installing an older version of Node.js.

Here are some of the most common scenarios full-stack developers encounter:

Testing Backwards Compatibility

Node.js has a fast release cycle, shipping new versions every 6 months. With each release, there is risk of breaking changes to the core API or breaking changes to dependencies in the larger JavaScript ecosystem.

When developing and maintaining modules that get used across projects, downgrading Node allows thorough compatibility testing against previous versions before publishing updates.

For example, you may test that a module originally written for Node.js v10 continues to work without issues all the way back to v6 using this technique.

Comparing Performance Across Versions

The performance profile of Node.js can drastically change between major releases depending on the V8 engine updates and architecture changes introduced.

Developers will often benchmark the same app workload across different major versions to quantify these performance differences. The results inform upgrade timing and strategy when balancing between new version features and slower performance.

Mimicking Production Environments

In a testing environment, it‘s useful to install the exact Node.js versions that are running your production infrastructure to prevent unexpected issues.

The same app code can behave differently between Node.js 8 and Node.js 16 for example due to changes in the JavaScript language support. Replicating production environment versions thus helps catch bugs that only manifest in older versions.

Using Deprecated Modules

The JavaScript package ecosystem evolves extremely quickly, and modules become outdated or unsupported on newer Node.js releases.

In cases where a project relies on a deprecated module without maintenance, downgrading to the latest supported Node.js version avoids having to immediately refactor to alternatives.

Now that we‘ve covered some of the common use cases for downgrading, let‘s look at how to interpret Node.js version numbers before moving onto the downgrade process.

Node.js Releases and Versioning Scheme

Node.js follows a rapid-release cycle, with a major version shipping every 6 months. Releases are identified by semantic version identifiers like v14.13.5 with the following meaning:

• v – Denotes a Node.js version number
• 14 – Represents the major version number
• 13 – Represents the minor version number
• 5 – Represents the patch version number

Major Releases

The major version (e.g. v14) focuses on major architecture changes and language feature updates powered by a new V8 JavaScript engine release.

They occur every 6 months in April and October, aligned with Google‘s V8 release cycle. These usually introduce breaking changes to Node.js APIs or change behavior in some way.

Minor Releases

The minor version contains incremental improvements to stability and performance on top of the major version features.

Minor releases happen monthly and are generally backwards compatible with the corresponding major release.

Patch releases

Patch releases (e.g. v14.13.5) consist of critical bug and security fixes. They try to avoid any breaking changes or behavior shifts when possible.

Patches are created whenever necessary, roughly every 1-2 weeks.

Understanding this release model informs whether a specific Node.js version meets your compatibility and support requirements when downgrading.

With this context covered, let‘s now look at how to downgrade Node.js on Ubuntu 20.04 LTS using the node version manager nvm.

Downgrading Node.js on Ubuntu 20.04 with nvm

nvm stands for Node Version Manager. As the name suggests, it allows you to easily install, manage and switch between multiple Node.js versions on your system.

Before we install nvm however, let‘s confirm our current Node.js version that will be downgraded:

node -v
# v18.12.1 - Current version

We are running the latest Current release of Node.js v18. Our aim is to downgrade to the previous Long-term Support version, v16.15.0, to mimic a common production environment version.

So first, we need to install nvm:

Step 1: Install nvm

To install or update nvm, run the installation script via curl:

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.3/install.sh | bash

This clones the nvm repository to ~/.nvm and adds the source lines to your profile (~/.bash_profile, ~/.zshrc, ~/.profile, or ~/.bashrc).

By default, you should restart your terminal or shell session anytime nvm is installed/updated for changes to apply.

Let‘s confirm everything works – check the version to verify it is installed:

nvm --version

# 0.39.3

Now we can leverage nvm to install and manage Node.js versions!

Step 2: Install Target Node Version

Checking the available versions, we can see v16.15.0 is among those available to install:

nvm ls-remote --lts

Run the following to install our target v16.15.0 LTS release:

nvm install 16.15.0

This will take a minute or two to download, compile, and install the version.

Step 3: Switch Versions

By default, the original Node.js v18 is still active. To activate the v16.15.0 version we just installed, enter:

nvm use 16.15.0

Check it is now running by printing the version:

node -v 

# v16.15.0

Success! We have downgraded from v18 to v16.15.0 LTS!

Note: This will only apply to the current shell session. When you open a new terminal or tab, it will default back to v18.

Let‘s make v16 the permanent default:

Step 4: Set Default Version

To set v16.15.0 as the new default Node.js version automatically, run:

nvm alias default 16.15.0

Now Node.js v16.15.0 will be loaded by default in all new shell sessions.

The full flow to downgrade is summarized below:

And within a few short commands, we have successfully downgraded Node.js to a older LTS version! Pretty easy right?

Next let‘s discuss some best practices when managing multiple versions.

Best Practices for Managing Multiple Versions

When working with different Node.js versions, here are some tips for avoiding headaches from my experience:

1. Isolate global packages

By default npm will install packages (like npm, @vue/cli, etc) in /usr/local/lib. This can cause conflicts across Node versions.

Instead, configure version-specific prefix configs in ~/.npmrc:

# ~/.npmrc
node_16_npm_prefix=/home/user/.nvm/v16.15.0/lib/node_modules
node_18_npm_prefix=/home/user/.nvm/v18.12.1/lib/node_modules 

npm_config_prefix=${node_16_npm_prefix} # Set dynamically based on version

This keeps global packages separate.

2. Reinstall version-specific dependencies

The node_modules folder housing your app dependencies is also version specific.

When switching between major versions with nvm use, run npm install to match the locked package requirements against the new Node.js capabilities.

3. Delete unused versions

Removing unused Node.js versions saves disk space. To delete e.g. v16.15.0, run:

nvm uninstall 16.15.0

Make sure any projects are not relying on the version first!

Having looked at some best practices, let‘s now compare a few other methods for downgrading.

Alternative Downgrading Options

While nvm is one of the most popular node version managers, here are a few alternatives worth mentioning:

NodeSource

NodeSource provides deb/rpm packages containing official Node binaries. You can install older versions by specifying the desired major Nodejs version:

# Install Node.js v4 Argon
curl -sL https://deb.nodesource.com/setup_4.x | sudo -E bash -
sudo apt-get install -y nodejs

node -v # v4.9.1

Manual Install

You can manually compile and install specific Node.js versions from source. While more complex, this offers maximum control.

This lets you dictate compile-time options and base system dependencies.

Distro Packages

Linux distributions ship packaged versions of Node.js in their repositories, but tend to heavily lag behind the latest releases.

If running a Ubuntu LTS version for stability however, the distro package might meet your version needs without requiring extra setup.

Evaluate whether any of these options better fit your specific downgrading use case!

With the various methods covered, let‘s round up with some troubleshooting tips for common issues.

Troubleshooting Downgrades

Here are solutions to a few common problems faced when downgrading Node.js versions:

Version not changing in shell

If issuing nvm use 8 for example doesn‘t update the node version in the same shell, run:

hash -r

This clears the cached path for Node executables so the shell picks up the new version.

Permissions errors

If seeing "Permission denied" errors when installing Node.js with nvm, prefix the install command with sudo:

sudo nvm install 10.15.0 

This temporary overrides permissions to install system-wide.

Missing Python / build tools

Some Node.js version installations rely on local compile-time dependencies like Python and Make.

Resolving error messages about missing packages with your distribution‘s package manager will unblock the nvm install process.

With this general troubleshooting advice, you should be equipped to resolve the most common downgrading issues.

Key Takeaways and Next Steps

We have covered a lot of ground discussing the ins and outs of downgrading Node.js!

Here are some key takeways as a quick recap:

• Downgrading Node.js enables testing backwards compatibility, performance comparisons, mimicking production, and using deprecated modules
• Node.js follows semantic versioning – understanding the difference between major, minor and patches informs compatibility decisions
• nvm enables seamless Node.js downgrades by enabling version switching
• Follow version management best practices around global packages and dependencies
• Alternative version managers like NodeSource and manual installs are also an option

Now you have a complete guide to confidently downgrade Node.js versions directly on Ubuntu systems as a developer!

Let me know in the comments if you have any other questions as you implement these learnings in practice. And as always, happy coding!