How to verify what modules are active on my server?

Question

While trying to solve a problem on my website, a recommendation about my .htaccess file I got was

First of all, please check on the server for all the different modules if they are enabled, and once they are, remove the

<IfModule
 ...></IfModule>

blocks. They are putting an unnecessary strain on your server.

I don't know where should I look to see if modules are active - is it in the CMS? in the httpd.conf file? in the files on my server? should I make a slight modification in the .htaccess as a test? But more than that, could the recommendation self be not appropriate? Thanks.

Here is the .htaccess file for which the recommendation has been made:

Options +FollowSymLinks -MultiViews
RewriteEngine on
AddHandler x-httpd-php .html .htm

<ifModule mod_gzip.c>
  mod_gzip_on Yes
  mod_gzip_dechunk Yes
  mod_gzip_item_include file \.(html?|txt|css|js|php|pl)$
  mod_gzip_item_include handler ^cgi-script$
  mod_gzip_item_include mime ^text/.*
  mod_gzip_item_include mime ^application/x-javascript.*
  mod_gzip_item_exclude mime ^image/.*
  mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*
</ifModule>

<ifModule mod_expires.c>
  ExpiresActive On
  ExpiresDefault "access plus 1 seconds"
  ExpiresByType text/html "access plus 1 seconds"
  ExpiresByType image/gif "access plus 2592000 seconds"
  ExpiresByType image/jpeg "access plus 2592000 seconds"
  ExpiresByType image/png "access plus 2592000 seconds"
  ExpiresByType text/css "access plus 2592000 seconds"
  ExpiresByType text/javascript "access plus 216000 seconds"
  ExpiresByType application/x-javascript "access plus 216000 seconds"
</ifModule>

<ifModule mod_headers.c>
  <filesMatch "\\.(ico|pdf|flv|jpg|jpeg|png|gif|swf)$">
    Header set Cache-Control "max-age=2592000, public"
  </filesMatch>

  <filesMatch "\\.(css)$">
    Header set Cache-Control "max-age=2592000, public"
  </filesMatch>

  <filesMatch "\\.(js)$">
    Header set Cache-Control "max-age=216000, private"
  </filesMatch>

  <filesMatch "\\.(xml|txt)$">
    Header set Cache-Control "max-age=216000, public, must-revalidate"
  </filesMatch>

  <filesMatch "\\.(html|htm|php)$">
    Header set Cache-Control "max-age=1, private, must-revalidate"
  </filesMatch>
</ifModule>

<ifModule mod_headers.c>
  Header unset ETag
</ifModule>

FileETag None

<ifModule mod_headers.c>
  Header unset Last-Modified
</ifModule>

RewriteCond %{HTTP_HOST} !^(www\.)?foo\.com$
RewriteRule .? http://foo.com%{REQUEST_URI} [R=301,L]

#BEGIN WordPress
<IfModule mod_rewrite.c>

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php

</IfModule>
# END WordPress

Answer 1

Assuming you mean apache modules you can run the below to list which modules you have loaded:

apachectl -t -D DUMP_MODULES

Answer 2

If PHP is run as apache module, you can use the phpinfo() function. Search for the Apache section (usually apache2handler) and look for the row with "Loaded Modules":

Answer 3

If you don't have those modules loaded then it doesn't look anything's going to break on your site, it's just not going to have the best cache control settings. So leave out the ifmodules as you can't even load them if they aren't loaded. The apache website says

In normal operation, directives need not be placed in sections.

http://httpd.apache.org/docs/2.0/mod/core.html#ifmodule