Install packages

## Ubuntu
sudo apt-get install ruby-full build-essential zlib1g-dev

## RHEL8/CentOS8
sudo dnf install ruby ruby-devel
sudo dnf group install "Development Tools"

Configure gem path

echo '# Install Ruby Gems to ~/gems' >> ~/.bashrc
echo 'export GEM_HOME="$HOME/gems"' >> ~/.bashrc
echo 'export PATH="$HOME/gems/bin:$PATH"' >> ~/.bashrc
source ~/.bashrc

Install jekyll & bundler

gem install jekyll bundler

Test your site

Goto your project directory

bundle exec jekyll serve

Updating the GitHub Pages gem

If the github-pages gem on your computer is out of date with the github-pages gem on the GitHub Pages server, your site may look different when built locally than when published on GitHub. To avoid this, regularly update the github-pages gem on your computer.

If you installed Bundler, run bundle update github-pages.
If you don’t have Bundler installed, run gem update github-pages.

If no Gemfile

bundle init
bundle add jekyll
bundle install --path vendor/bundle