Can I run one Craft install on multiple domains and/or subdomains? Is it possible to have one Craft install running multiple domains and/or subdomains?

For example having the same Craft install running a blog Channel at blog.example.com and also an about Single at example.com/about.
Update for Craft 3

Craft 3 includes native support for multi-site installation. Here's a link to the official docs and here's a link to another question with more resources.

Old answer for Craft 1 &amp; 2

Credit to @LukeHolder for the original answer, but here's a bit more detailed and technical answer. Note, this might not be possible on all hosts.

Place the craft folder above both domains, add Craft's index.php file to both domain web roots and set the $craftPath variables in them to point to the same craft folder.

To make a template (say for a blog) only load on its own subdomain instead of whenever any of its slugs are requested on any domains you can run this quick check:

{% set domain = craft.request.getServerName() %}

{% if not domain starts with 'blog' %}
    {% redirect '404' %}
{% endif %}


This will make "blog.example.com/some-blog-post" load, but "example.com/some-blog-post" will redirect to the 404 page.

Links to posts can formatted like this to add the subdomain to the URL:

http://blog.example.com/{{ entry.uri }}


While this isn't an end all solution, it is a functional workaround, especially if it's only for page or two. Use Craft 3 if you can.