How to enable SSI (Server Side Include) support on an Apache web server
Server Side Include (or SSI) is a useful feature that enables
you to do things like include files into your web pages. The most
common use for this feature is to allow you to design a navigation bar,
put it in a separate file and then include that in all of your web
pages. When you need to change the navigation bar you change just the
include file, not every web page on your server. The change in the
include file simply propogates through all the pages that include it.
Configuring Apache to enable SSI
The first thing to do is ensure that your server has the mod_include
module installed and enabled. Most Linux systems come with this
preconfigured so you should not have to worry about this.
The next step is to edit your httpd.conf file to enable Includes. You
will typically find this file in /etc/httpd/conf. The directive that
needs to be set is as follows:
Not all files will automatically support SSI and the recommended
practice is that you do not configure your server so that all files
support SSI. Web pages that support SSI must be scanned by the server
for includes before they are displayed putting a extra overhead on the
performance of the system. It is better to only have the server perform
that for pages that actually contain includes. This can be achieved in
a number of ways:
- Apache can be configured to parse any file with a particular file
extension, such as .shtml, with the following directives
in the http.conf file:
This is a great approach when you know in advance whether a page
needs to use server side includes or not but can be a problem if you
need to change an existing page since you would have to rename the page
to use the new filename extension and also change any links that point
to this file.
- Use the XBitHack directive in the httpd.conf file:
XBitHack tells the Apache server to parse files for SSI
directives if they have the execute bit set. In other words, to add SSI
directives to an existing page, you simply need to make the file
executable using the chmod command. For example:
chmod +x mypage.html
NOTE: When experimenting with
pages that support SSI it is important to ensure the pages are actually
served up by the Apache web server. A common mistake web designers make
is to work on local HTML files in a work directory and directly open
the web pages in a browser. In this situation the SSI includes are not
activated because the pages are not being handled by the web server.
When testing always upload the pages to the web server.
Example SSI Directives
Now that you have SSI working on your Apache web server here are some
useful examples SSI directive in action.