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Comments and suggestions concerning this book should be mailed to gmourani@videotron.ca © Copyright 1999-2000 Gerhard Mourani and Open Network Architecture ® 348 This option “cache_mem” specifies the amount of memory (RAM) to be used for caching the so called: In-Transit objects, Hot Objects, Negative-Cached objects. This is an optimization feature. It’s important to note that Squid can uses much more MB than the value you specify in this parameter and for this reason, if you have 48 MB free for Squid, you must put 48/3 = 16 MB here. cache_dir ufs /cache 200 16 256 This option “cache_dir” specify in order: which  kind of storage system to use (ufs), the  name of the cache directory (/cache) of Squid, the disk space in megabytes to use under this directory (200 Mbytes), the number of first-level subdirectories to be created under the cache directory (16 Level-1), and the number of second-level subdirectories to be created under each first-level cache directory (256 Level-2). In accelerator mode, this option is directly related with the size of all files you want to serve with your Apache web server. emulate_httpd_log on This option “emulate_httpd_log” if set to “ON” specifies Squid to emulate the log file format of Apache web server. This is very useful if you want to use a third party program like Webalizer to analyze Web Server (httpd) log file. redirect_rewrites_host_header off This option “redirect_rewrites_host_header” if set to “OFF”, specify Squid to not rewrites any Host: header in redirected requests. It’s recommended to set this option to “OFF” if you are running Squid in accelerator mode. replacement_policy GDSF This option “replacement_policy” specify the cache policy Squid will use to determine which objects in the cache must be replaced when the proxy need to make disk space. The Squid LRU policy is used by default if you are not specifying the “--enable-heap-replacement” option during the compile time. In our configuration, we choose the GDSF (Greedy-Dual Size Frequency) policy as our default policy. See  http://www.hpl.hp.com/techreports/1999/HPL-1999-69.html and http://fog.hpl.external.hp.com/techreports/98/HPL-98-173.html for more information. acl all src 0.0.0.0/0.0.0.0 and http_access allow all These options “acl and http_access” specifies and define an access control lists to be applied on the proxy server Squid. Our “acl” and “http_access” options are not restriction and allow every one to connect on the proxy server since we use this proxy to accelerate the public Apache Web Server. See your Squid documentation for more information when using Squid in non-accelerator mode. cache_mgr admin This option “cache_mgr” specify the email-address of the administrator responsible of the Squid proxy server. This person is the one who will receive mail if Squid encounter problems. You can specify the name or the complete email address in this option. cache_effective_user squid and cache_effective_group squid These options “cache_effective_user and cache_effective_group” specify the UID/GID the cache will run on. Don’t forget to never run Squid as “root”. In our configuration we use the UID “squid” and the GID “squid”. httpd_accel_host 208.164.186.3 and httpd_accel_port 80 These options “httpd_accel_host and httpd_accel_port” specify to Squid the IP address and port number where the real HTTP Server (i.e. Apache) is. In our configuration, the real HTTP Web Server is on the IP address 208.164.186.3 (www.openarch.com) and on the port (80). The www.openarch.com is another host name on our network and since the Squid Proxy Server doesn’t reside on the same host of Apache HTTP Web Server, then we can use the port (80) for our Squid Proxy Server, and the port (80) for our Apache Web Server and the illusion is perfect.