How to configure mod_expires module in Apache?

To configure the mod\_expires module in Apache, follow the steps below:

1. Firstly, make sure that the mod\_expires module is enabled. You can do this by executing the following command:

`sudo a2enmod expires`

1. Once the module is enabled, you can configure it directly from your Apache configuration file (httpd.conf or apache2.conf depending on your OS), or via an .htaccess file in the directory of the files you want to apply the configuration to (the latter option is typically used for shared hosting).

1. In the configuration file, you can use the `ExpiresActive` directive to turn on the module, the `ExpiresDefault` to define the default expiration time and the `ExpiresByType` to specify different expiration times based on file type.

Here is an example configuration:

```
ExpiresActive On ExpiresDefault “access plus 1 month“ ExpiresByType image/jpg “access plus 1 year“ ExpiresByType image/jpeg “access plus 1 year“ ExpiresByType image/gif “access plus 1 year“ ExpiresByType image/png “access plus 1 year“ ExpiresByType text/css “access plus 1 month“ ExpiresByType text/html “access plus 1 month“ ExpiresByType application/pdf “access plus 1 month“ ExpiresByType text/x-javascript “access plus 1 month“ ExpiresByType application/x-shockwave-flash “access plus 1 month“ ExpiresByType image/x-icon “access plus 1 year”

```

In this sample configuration, images will be cached by web browsers for a year, while HTML, CSS, JavaScript, PDFs and Flash will be cached for a month.

1. Save the changes to the file, then restart Apache so the changes take effect. This can be done using the following command:

`sudo systemctl restart apache2`

Keep in mind that incorrect settings in the Apache configuration file can bring down your server, so always make sure to back up your configuration file before making any changes.