Squid: Configuring an Ubuntu host to use a Squid proxy for internet access

Once you have a Squid proxy setup as described in my article here, the next challenge is configuring your Ubuntu servers so that they use this proxy by default instead of attempting direct internet connections.

There are several entities we want using Squid by default: apt package manager, interactive consoles and wget/curl, and Java applications.

Apt package manager

First we install some dependent packages:

> sudo apt-get install python-apt apt-transport-https python3-pycurl software-properties-common -y

Then create a file named ‘/etc/apt/apt.conf.d/00proxy’ with the content below.  Replace with the IP of your specific Squid host.

Acquire::http::Proxy "";
Acquire::https::Proxy "";
Acquire::ftp::Proxy "";

Then do an apt-get update:

> sudo apt-get update

Login to the squid server and open the ‘/var/log/squid3/access.log’ for evidence that the apt-get call was made through the proxy.

Unattended upgrades will use the proxy as well, if you want to enable unattended upgrades, read my article here.

Interactive console and wget/curl

Append the text below to ‘/etc/bash.bashrc’, ‘/etc/profile’, ‘/etc/environment’, and ‘/etc/wgetrc’.  We will pretend that the Squid proxy is located at, replace this with your squid server address.

export http_proxy=
export https_proxy=
export ftp_proxy=
export no_proxy=

In ‘/etc/wgetrc’, also add the line:


After logging out and logging back in, you should be able to use wget to retrieve page below if squid has whitelisted the domain:

> wget http://wiki.squid-cache.org

And for curl:

curl http://wiki.squid-cache.org

Login to the squid server and open the ‘/var/log/squid3/access.log’ for evidence that the call was made through the proxy.

If you want to force wget to use a proxy, you can pass the environment variables directly to wget:

wget -e use_proxy=yes -e http_proxy=\ https_proxy= http://wiki.squid-cache.org

If you want to force curl to use a proxy, you can pass the proxy host directly to curl:

curl -x http://wiki.squid-cache.org

Java applications

Java application needs JVM system properties set that refer to the Squid proxy: http.proxyHost, http.proxyPort, https.proxyHost, and https.proxyPort are the most pertinent to our conversation here, but here is a full listing.

Using the Java program below as an example:

import java.io.*;
 import java.net.*;

public class SquidTest {

public static void main(String args[]) throws Exception {

String urlToRead = "http://wiki.squid-cache.org";
 if(args.length>0) {
 urlToRead = args[0];
 System.err.println("urlToRead: " + urlToRead);

StringBuilder result = new StringBuilder();
 URL url = new URL(urlToRead);
 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
 BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
 String line;
 while ((line = rd.readLine()) != null) {

} // main

} // class

If you compile then run the application with the JVM system properties pointing to the Squid proxy, then you should see the request going through the Squid server access logs.

> javac -classpath . SquidTest.java

> java -classpath . \
-Dhttp.proxyHost= -Dhttp.proxyPort=3128 \
-Dhttps.proxyHost= -Dhttps.proxyPort=3128 \
 -Dhttp.agent=jvmtest \
SquidTest http://wiki.squid-cache.org