File: //etc/apache2/conf-available/cache.conf
<IfModule mod_expires.c>
    ExpiresActive On
    ExpiresDefault "access plus 1 hour"
    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 application/javascript "access plus 1 month"
    ExpiresByType text/javascript "access plus 1 month"
    ExpiresByType text/html "access plus 1 hour"
</IfModule>
<IfModule mod_cache.c>
    CacheRoot /var/cache/apache2/mod_cache_disk
    CacheEnable disk /
    CacheDirLevels 2
    CacheDirLength 1
</IfModule>