How Do I Fix Nokogiri Installation Error on Ruby 1.8.7 in Linux

When I was setting up a Rails 3.2.1 project with Ruby 1.8.7 on a Linux WHM server, I ran into a frustrating issue while trying to install the Nokogiri gem. Nokogiri is essential because it helps with parsing XML and HTML, and in my case, I needed it for working with the Authorize.net gem.

I’ll walk you through what went wrong, how I figured it out, and how I tested Nokogiri with some practice coding once it was installed.

The First Code I Ran

The very first step I tried was installing Nokogiri with:

gem install nokogiri -v '1.5.0'

I expected it to just work. Instead, I got hit with this error:

checking for libxslt/xslt.h... no
libxslt is missing.

And later, when I tried to install libxslt-ruby, I ran into another error:

error: ruby/io.h: No such file or directory

Understanding the Error

At first glance, these errors seemed cryptic. But breaking them down made the root cause clear:

• libxslt missing: Nokogiri depends on two system libraries libxml2 and libxslt. My Linux server didn’t have the development headers for libxslt installed, so the gem couldn’t compile its native C extensions.
• ruby/io.h missing: This header file belongs to Ruby’s core development package. While Ruby was installed, the “-devel” package (which provides compilation headers like ruby/io.h) wasn’t. Without it, building gems with native extensions is impossible.

In short: my system was missing the development libraries Nokogiri needed.

Installing the Right Dependencies

The fix turned out to be installing the missing system packages. Depending on the Linux distribution, here’s how I did it:

For CentOS/RedHat:

yum install -y libxml2-devel libxslt-devel ruby-devel make gcc

For Ubuntu/Debian:

sudo apt-get install -y build-essential libxml2-dev libxslt1-dev ruby-dev zlib1g-dev

Once I had these installed, running:

gem install nokogiri -v '1.5.0'

finally worked.

Practicing with Nokogiri

After resolving the installation problem, I wanted to test Nokogiri right away. I wrote a small Ruby script to practice parsing an HTML page.

# test_nokogiri.rb
require 'nokogiri'
require 'open-uri'

# Fetch and parse an HTML document
url = "https://www.ruby-lang.org/en/"
doc = Nokogiri::HTML(URI.open(url))

puts "Page title: #{doc.at('title').text}"

# Extract all links
puts "\nLinks found on the page:"
doc.css('a').each_with_index do |link, i|
  puts "#{i + 1}. #{link.text.strip} -> #{link['href']}"
end

# Count paragraphs
paragraphs = doc.css('p')
puts "\nTotal paragraphs: #{paragraphs.count}"

# Show the first paragraph
if paragraphs.any?
  puts "\nFirst paragraph:\n#{paragraphs.first.text.strip}"
end

Running the script:

ruby test_nokogiri.rb

What it does:

• Reads the Ruby website homepage
• Prints the page <title>
• Lists all links with their text and URLs
• Counts how many <p> tags there are
• Displays the first paragraph

This gave me confidence that Nokogiri was working as expected.

Final Thoughts

At first, I thought the Nokogiri installation error was something wrong with RubyGems or the gem itself. But in reality, it was simply missing system dependencies. Once I installed libxml2, libxslt, and Ruby development headers, everything fell into place. The key takeaway for me is this: whenever a Ruby gem fails to build native extensions, check for missing development libraries. It saves hours of frustration.