I am currently running 2.5.3. Official Jekyll docs provide the resource Upgrading from 2.x to 3.x, which outlines some of the known changes I will need to make to older Jekyll sites. I will document any useful findings as I upgrade.

First, update Jekyll gem.

sudo gem update jekyll

Updating installed gems
Updating jekyll Fetching: jekyll-3.0.1.gem (100%)^[[C
Successfully installed jekyll-3.0.1
Parsing documentation for jekyll-3.0.1
Installing ri documentation for jekyll-3.0.1
Installing darkfish documentation for jekyll-3.0.1
Done installing documentation for jekyll after 9 seconds
Parsing documentation for jekyll-3.0.1
Done installing documentation for jekyll after 2 seconds
Gems updated: jekyll

That was nice. Now, I’ll run this site locally and see what I’ll need to address.

$ cd jvaage && jekyll serve --watch

Liquid Exception: Liquid syntax error: Unknown tag ‘gist’

This was expected as the jekyll-gist gem is listed as no longer included.

Concerning Dependencies

We dropped a number of dependencies the Core Team felt were optional. As such, in 3.0, they must be explicitly installed and included if you use any of the features. - Jekyll Docs: Dropped Dependencies.

Explicitly install some formally included plugins. Easy enough.

gem install jekyll-gist.rb

Another former dependecy, Pygments, provided syntax highlighting. Now, Rouge is the Jekyll default. Note: the highlight tag will still work, however you should read about what changes might affect your usage of that tag. If you are not adverse to explicitly installing gems and want to continue using Pygments:

gem install pygments.rb

That is all. I will update this post with any findings I make running the several other Jekyll sites I manage.