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  • Book Overview & Buying Squid Proxy Server 3.1: Beginner's Guide
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Squid Proxy Server 3.1: Beginner's Guide

Squid Proxy Server 3.1: Beginner's Guide

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Squid Proxy Server 3.1: Beginner's Guide

Squid Proxy Server 3.1: Beginner's Guide

4.7 (13)
Buy this Book

Overview of this book

Squid Proxy Server enables you to cache your web content and return it quickly on subsequent requests. System administrators often struggle with delays and too much bandwidth being used, but Squid solves these problems by handling requests locally. By deploying Squid in accelerator mode, requests are handled faster than on normal web servers making your site perform quicker than everyone else's! Squid Proxy Server 3.1 Beginner's Guide will help you to install and configure Squid so that it is optimized to enhance the performance of your network. The Squid Proxy Server reduces the amount of effort that you will have to put in, saving your time to get the most out of your network. Whether you only run one site, or are in charge of a whole network, Squid is an invaluable tool that improves performance immeasurably. Caching and performance optimization usually requires a lot of work on the developer's part, but Squid does all that for you. This book will show you how to get the most out of Squid by customizing it for your network. You will learn about the different configuration options available and the transparent and accelerated modes that enable you to focus on particular areas of your network. Applying proxy servers to large networks can be a lot of work as you have to decide where to place restrictions and who should have access, but the straightforward examples in this book will guide you through step by step so that you will have a proxy server that covers all areas of your network by the time you finish the book.
Table of Contents (20 chapters)
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Squid Proxy Server 3.1 Beginner's Guide
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Squid Proxy Server 3.1 Beginner's Guide
Credits
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Credits
About the Author
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About the Author
About the Reviewers
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About the Reviewers
www.PacktPub.com
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www.PacktPub.com
Preface
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Preface
Lock Free Chapter
1
Getting Started with Squid
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Getting Started with Squid
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Proxy server
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Reverse proxy
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Getting Squid
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Time for action – identifying the right version
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Time for action – downloading Squid
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Time for action – using Bazaar to obtain source code
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Installing Squid
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Time for action – running the configure command
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Time for action – compiling the source
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Time for action – installing Squid
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Time for action – exploring Squid files
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Summary
2
Configuring Squid
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Configuring Squid
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Quick start
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Syntax of the configuration file
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HTTP port
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Time for action – setting the HTTP port
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Access control lists
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Time for action – constructing simple ACLs
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Controlling access to the proxy server
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Time for action – combining ACLs and HTTP access
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Cache peers or neighbors
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Time for action – adding a cache peer
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Caching web documents
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Time for action – specifying space for memory caching
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Time for action – creating a cache directory
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Time for action – adding a cache directory
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Tuning Squid for enhanced caching
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Time for action – preventing the caching of local content
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Time for action – calculating the freshness of cached objects
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Playing around with HTTP headers
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DNS server configuration
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Time for action – adding DNS name servers
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Logging
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URL rewriters and redirectors
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Other configuration directives
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Summary
3
Running Squid
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Running Squid
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Command line options
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Time for action – listing the options
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Time for action – finding out the Squid version
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Time for action – creating cache directories
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Time for action – debugging output in the console
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Time for action – testing our configuration file
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Automatically starting Squid at system startup
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Time for action – adding the init script
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Summary
4
Getting Started with Squid's Powerful ACLs and Access Rules
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Getting Started with Squid's Powerful ACLs and Access Rules
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Access control lists
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Time for action – constructing ACL lists using IP addresses
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Time for action – using a range of IP addresses to build ACL lists
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Time for action – constructing ACL lists using domain names
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Time for action – building ACL lists using destination ports
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Time for action – using a request protocol to construct access rules
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Time for action – enforcing proxy authentication
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Access list rules
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Time for action – denying miss_access to neighbors
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Mixing ACL lists and rules – example scenarios
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Time for action – avoiding caching of local content
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Time for action – blocking video content
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Time for action – writing rules for special access
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Testing access control with squidclient
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Time for action – testing our access control example with squidclient
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Time for action – testing a complex access control
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Summary
5
Understanding Log Files and Log Formats
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Understanding Log Files and Log Formats
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Log messages
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Cache log or debug log
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Time for action – understanding the cache log
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Access log
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Time for action – understanding the access log messages
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Time for action – analyzing a syntax to specify access log
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Time for action – learning log format and format codes
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Time for action – customizing the access log with a new log format
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Selective logging of requests
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Time for action – using access_log to control logging of requests
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Referer log
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Time for action – enabling the referer log
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Time for action – translating the referer logs to a human-readable format
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User agent log
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Time for action – enabling user agent logging
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Emulating HTTP server-like logs
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Time for action – enabling HTTP server log emulation
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Log file rotation
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Other log related features
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Summary
6
Managing Squid and Monitoring Traffic
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Managing Squid and Monitoring Traffic
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Cache manager
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Time for action – installing Apache Web server
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Time for action – configuring Apache to use cachemgr.cgi
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Log file analyzers
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Time for action – installing Calamaris
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Time for action – generating stats in plain text format
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Time for action – generating graphical reports with Calamaris
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Summary
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Protecting your Squid Proxy Server with Authentication
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Protecting your Squid Proxy Server with Authentication
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HTTP authentication
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Basic authentication
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Time for action – exploring Basic authentication
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Time for action – configuring NCSA authentication
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Time for action – configuring PAM service
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Time for action – configuring MSNT authentication
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Time for action – configuring Squid to use SASL authentication
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Time for action – configuring RADIUS authentication
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Digest authentication
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Time for action – configuring Digest authentication
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Microsoft NTLM authentication
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Negotiate authentication
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Time for action – configuring Negotiate authentication
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Using multiple authentication schemes
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Writing a custom authentication helper
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Time for action – writing a helper program
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Making non-concurrent helpers concurrent
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Common issues with authentication
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Summary
8
Building a Hierarchy of Squid Caches
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Building a Hierarchy of Squid Caches
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Cache hierarchies
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Reasons to use hierarchical caching
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Problems with hierarchical caching
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Joining a cache hierarchy
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Time for action – joining a cache hierarchy
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Controlling communication with peers
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Time for action – configuring Squid for domain-based forwarding
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Time for action – forwarding requests to cache peers using ACLs
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Time for action – configuring Squid to switch peer relationship
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Peer communication protocols
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Summary
9
Squid in Reverse Proxy Mode
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Squid in Reverse Proxy Mode
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What is reverse proxy mode?
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Configuring Squid as a server surrogate
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HTTP port
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HTTPS port
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Time for action – adding backend web servers
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Logging messages in web server log format
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Time for action – configuring Squid to ignore the browser reloads
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Access controls in reverse proxy mode
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Summary
10
Squid in Intercept Mode
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Squid in Intercept Mode
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Interception caching
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Time for action – understanding interception caching
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Advantages of interception caching
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Problems with interception caching
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Diverting HTTP traffic to Squid
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Time for action – enabling IP forwarding
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Time for action – redirecting HTTP traffic to Squid
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Summary
11
Writing URL Redirectors and Rewriters
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Writing URL Redirectors and Rewriters
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URL redirectors and rewriters
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Squid, URL redirectors, and rewriters
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Time for action – exploring the message flow between Squid and redirectors
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Time for action – writing a simple URL redirector program
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Writing our own URL redirector program
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Time for action – writing our own template for a URL redirector
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Configuring Squid
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A special URL redirector – deny_info
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Popular URL redirectors
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Summary
12
Troubleshooting Squid
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Troubleshooting Squid
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Some common issues
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Time for action – changing the ownership of log files
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Time for action – fixing cache directory permissions
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Time for action – creating swap directories
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Time for action – finding the program listening on a specific port
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Debugging problems
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Time for action – debugging HTTP requests
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Time for action – debugging access control
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Summary
1
Pop Quiz Answers
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Pop Quiz Answers
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Chapter 1, Getting Started with Squid
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Chapter 2, Configuring Squid
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Chapter 3, Running Squid
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Chapter 4, Getting Started with Squid’s Powerful ACLs and Access Rules
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Chapter 5, Understanding Log Files and Log Formats
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Chapter 6, Managing Squid and Monitoring Traffic
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Chapter 7, Protecting your Squid with Authentication
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Chapter 8, Building a Hierarchy of Squid Caches
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Chapter 9, Squid in Reverse Proxy Mode
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Chapter 10, Squid in Intercept Mode
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Chapter 11: Writing URL Redirectors and Rewriters
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Chapter 12: Troubleshooting Squid
2
Index
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Index

Time for action – debugging access control

Normally, it's easy to construct ACLs using various ACL types and they will work as expected. However, as our configuration gets bigger, ACLs may get confusing and it'll be hard to point out the exact culprit ACL causing problems such as, access denied messages or allowing access to a denied object. To debug our ACLs in such a situation, we can take advantage of the debug_options directive so that we can see the step-by-step processing of ACLs by Squid. We'll learn to debug our example configuration.

Consider the following access control lines in our configuration file:

acl example dstdomain .example.com
acl png urlpath_regex -i \.png$

http_access deny png example
http_access allow localhost
http_access allow localnet
http_access deny all

If we consult the table of section numbers for the Squid components, the section number for access control is 28. So, we will add the following line to our configuration file:

debug_options ALL,1 28,3

The previous...

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