sudo apt-get install varnish

vim /etc/default/varnish

DAEMON_OPTS="-a :80 \
             -T localhost:6082 \
             -f /etc/varnish/default.vcl \
             -S /etc/varnish/secret \
             -s file,/var/lib/varnish/$INSTANCE/varnish_storage.bin,1G

vim /etc/varnish/default.vcl

backend apache {
        .host = "127.0.0.1";
        .port = "8008";
}
acl purge {
        "localhost";
        "127.0.0.1";
}
sub vcl_recv {
        // Strip cookies for static files:
        if (req.url ~ "\.(jpg|jpeg|gif|png|ico|css|zip|tgz|gz|rar|bz2|pdf|txt|tar|wav|bmp|rtf|js|flv|swf|html|htm)$") {
                unset req.http.Cookie;
                return(lookup);
        }
        // Remove has_js and Google Analytics __* cookies.
        set req.http.Cookie = regsuball(req.http.Cookie, "(^|;\s*)(__[a-z]+|has_js)=[^;]*", "");
        // Remove a ";" prefix, if present.
        set req.http.Cookie = regsub(req.http.Cookie, "^;\s*", "");
        // Remove empty cookies.
        if (req.http.Cookie ~ "^\s*$") {
                unset req.http.Cookie;
        }
        if (req.request == "PURGE") {
                if (!client.ip ~ purge) {
                        error 405 "Not allowed.";
                }
                purge("req.url ~ " req.url " && req.http.host == " req.http.host);
                error 200 "Purged.";
        }
}
sub vcl_hash {
  if (req.http.Cookie) {
    set req.hash += req.http.Cookie;
  }
}
sub vcl_fetch {
        // Strip cookies for static files:
        if (req.url ~ "\.(jpg|jpeg|gif|png|ico|css|zip|tgz|gz|rar|bz2|pdf|txt|tar|wav|bmp|rtf|js|flv|swf|html|htm)$") {
                unset beresp.http.set-cookie;
        }
        // Varnish determined the object was not cacheable
        if (!beresp.cacheable) {
                set beresp.http.X-Cacheable = "NO:Not Cacheable";
        } elsif(req.http.Cookie ~"(UserID|_session)") {
            // You don't wish to cache content for logged in users
                set beresp.http.X-Cacheable = "NO:Got Session";
                return(pass);
        }  elsif ( beresp.http.Cache-Control ~ "private") {
                 // You are respecting the Cache-Control=private header from the backend
                set beresp.http.X-Cacheable = "NO:Cache-Control=private";
                return(pass);
        } elsif ( beresp.ttl < 1s ) {
                // You are extending the lifetime of the object artificially
                set beresp.ttl   = 300s;
                set beresp.grace = 300s;
                set beresp.http.X-Cacheable = "YES:Forced";
        }  else {
                // Varnish determined the object was cacheable
                set beresp.http.X-Cacheable = "YES";
        }
        return(deliver);
}

vim /etc/apache2/ports.conf

NameVirtualHost *:8008
Listen 8008

vim /etc/apache2/sites-enabled/000-default
<Virtualhost *:8008>
 ...
</Virtualhost>

service apache2 restart
service varnish restart

curl -I http://www.euperia.com/linux/setting-up-varnish-with-apache-tutorial/

HTTP/1.1 200 OK
Server: Apache
X-Pingback: http://www.euperia.com/xmlrpc.php
Link: ; rel=shortlink
Vary: Accept-Encoding,User-Agent
Content-Type: text/html; charset=UTF-8
X-Cacheable: YES
Content-Length: 22992
Date: Wed, 05 Jan 2011 22:01:22 GMT
X-Varnish: 769719461 769719459
Age: 7
Via: 1.1 varnish
Connection: keep-alive