Jekyll supports a lot of themes, which work quite well out of the box. A theme is a pre-defined set of styles, templates, and template variables. My site is based on the default Jekyll theme: minima. I had to do some customizations to make it work as I wish. Luckily, Jekyll allows customizations of almost everything of the theme. This post shows some of the customizations this site applies on top of minima.


Override theme defaults

The command bundle show minima can be used to find the location where the theme artifacts are installed, e.g.:

[]$ tree $(bundle show minima)
|-- LICENSE.txt
|-- _includes
|   |-- disqus_comments.html
|   |-- footer.html
|   |-- google-analytics.html
|   |-- head.html
|   |-- header.html
|   |-- icon-github.html
|   |-- icon-github.svg
|   |-- icon-twitter.html
|   `-- icon-twitter.svg
|-- _layouts
|   |-- default.html
|   |-- home.html
|   |-- page.html
|   `-- post.html
|-- _sass
|   |-- minima
|   |   |-- _base.scss
|   |   |-- _layout.scss
|   |   `-- _syntax-highlighting.scss
|   `-- minima.scss
`-- assets
    `-- main.scss

5 directories, 20 files

To override the theme defaults, simply copy the related file from the theme installation location to your project, under the same folder. For example, the following customization adds feed link in the header:

[]$ diff .bundle/gems/minima-2.1.1/_includes/header.html _includes/header.html
>           <a class="page-link" href="/feed.xml"><i class="fa fa-rss" aria-hidden="true"></i></a>

As another example, to include custom styles, make a copy of the main.scss file and add lines to import from any custom style sheets.

[]$ diff .bundle/gems/minima-2.1.1/assets/main.scss assets/main.scss
> @import "custom";
[]$ ls _sass/

By default, bundler installs gems in a central location shared by all ruby projects. To change that, set BUNDLE_DISABLE_SHARED_GEMS to true in the bundler config file, e.g.:

cat .bundle/config

Pagination of the home page

By default, the minima’s home page shows the complete list of posts, which is not nice. What I would prefer are:

  1. split the home page into multiple pages, if that list become long
  2. control the number of posts displayed per page
  3. link from each page to the previous and next pages

It turns out that Jekyll already has some support for pagination. To enable it, one has to add a line to the _config.yml file, specifying the number of items per page, e.g.: paginator: 8. With pagination enabled, Jekyll populates a paginator liquid object.

The following diff shows my changes to the default home layout, demonstrating the use of the paginator object:

[]$ diff .bundle/gems/minima-2.1.1/_layouts/home.html _layouts/home.html
<   <h1 class="page-heading">Posts</h1>
>   <h1 class="post-title">Posts</h1>
<     {% for post in site.posts %}
>     {% for post in paginator.posts %}
>         {{ post.excerpt | strip_html | replace_first: 'Contents', '' | lstrip | truncatewords: 40, "" }}<a href="{{ post.url | relative_url }}">&hellip; read more &raquo;</a>
<   <p class="rss-subscribe">subscribe <a href="{{ "/feed.xml" | relative_url }}">via RSS</a></p>
>   {% include prev_next.html prev_url=paginator.previous_page_path prev_text='Previous page' next_url=paginator.next_page_path next_text='Next page' %}

Basically, instead of iterating over site.posts, one has to loop over paginator.posts. In addition, pagination only works with the index.html file, which references the home layout. I also had to rename the file (default) to index.html to fix this error:

Pagination: Pagination is enabled, but I couldn't find an index.html page to use as the pagination template. Skipping pagination.

The links to the previous and next pages are implemented as a macro in the prev_next.html file. The macro requires four named parameters: prev_url, prev_text, next_url, and next_text. This line includes the macro and passes the required parameters:

{% include prev_next.html prev_url=paginator.previous_page_path prev_text='Previous page' next_url=paginator.next_page_path next_text='Next page' %}

The same macro is reused by the post layout to render the links to the previous and next posts.

As a side note, Jekyll pagination automatically generates the <link> tags with rel="next" and rel="prev" attributes as recommended by Google. Those tags reside in the <head> section of of the HTML page. They are not to be mixed up with the hyperlinks generated by the above macro.

Categories and tags

Categories and tags are two largely overlapping concepts in Jekyll. From a product perspective, I doubt the necessity of having both implemented, which do not provide added value instead of confusing the users. The only difference seems to be that categories become a part of the post URL. That means, a post having the category: hadoop in the front matter would have a URL like, where hadoop is the category. That also means, posts published on the same date (or in the same month or year) will be put into different folders, if they are of different categories. I do not like that. One could also customize the permalink pattern in Jekyll to remove the categories from the URL. But I chose to set the categories of all posts to post, e.g., the front matter of this post is:

layout: post
title:  "Customizing Jekyll theme"
date:   2017-12-23 07:56:11 +0000
last_modified_at: 2017-12-31 14:05:16
category: post
tags: [Blogging, Jekyll]

This way all posts go to the post category, which is simple and clear. The tags are used to generate a tags page, where all the posts are indexed by tags. The page generation code can be found here.


This post showed how to customize a theme in Jekyll, how to paginate the home page, how to generate links to navigate to the neighbouring pages, and discussed a bit about categories and tags. A separate post covers how to automatically generate the table of contents in Jekyll.