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Disclaimer: This manual is NOT a Squid tutorial. It is only a reference material that provides detailed explanation of all configuration parameters available in Squid 2.6. The reader is expected to have prior knowledge of basic Squid installation and configuration. For Complete tutorial on Squid, please visit http://www.squid-cache.org

Squid 2.6 Configuration Manual OPTIONS FOR EXTERNAL SUPPORT PROGRAMS External support programs could be viewed as a simple means of modular design, allowing third parties to write modules to improve the features of Squid. That's being said, some of Squid's standard functionality is also provided by helper programs. The standard helper programs include dnsserver, pinger, and several authentication modules. Third party modules include redirectors, ad blockers, and additional authentication modules. ftp_user ftp_list_width ftp_passive ftp_sanitycheck ftp_telnet_protocol check_hostnames allow_underscore cache_dns_program dns_children dns_retransmit_interval dns_timeout dns_defnames dns_nameservers hosts_file diskd_program unlinkd_program pinger_program url_rewrite_program url_rewrite_children url_rewrite_concurrency url_rewrite_host_header url_rewrite_access location_rewrite_program location_rewrite_children location_rewrite_concurrency location_rewrite_access auth_param authenticate_cache_garbage_interval authenticate_ttl authenticate_ip_ttl external_acl_type Recommended minimum configuration

TAG NAME                   ftp_user Description  This is the email address Squid uses to login to remote FTP servers anonymously Build Option  Default Usage  ftp_user username Default  ftp_user squid@ Synopsis For login to some servers, an anonymous email address is to be used. This tag is used to provide the anonymous email address for the login. This can simply be a user name followed by an @ symbol, which your domain name can be automatically attached to. Or it can be a full email address. This should be something reasonable for your domain, such as wwwuser@mydomain.com, or in the domainless case first mentioned, squid@, which happens to be the default for this option. Arguments username  User name to be used while login Example(s) ftp_user squid@squid.visolve.com       TAG NAME                   ftp_list_width Description  The column width for auto-generated Web pages of FTP sites queried through Squid when Squid is in forward proxy  mode Build Option  Default Usage  ftp_list_width number Default  ftp_list_width 32 Synopsis This tag gives some control over how Squid formats the resulting file lists. Squid provides limited FTP proxy features to allow browsers (even older, non-FTP aware browsers) to communicate with FTP servers. Arguments number  Column width Example(s) ftp_list_width 48       TAG NAME                   ftp_passive Description  If your firewall does not allow Squid to use passive connections, then turn off this option Build Option  Default Usage  ftp_passive on|off Default  ftp_passive on Synopsis Enable or disable passive connections. Arguments on/off  Enable or disable this option       TAG NAME                   ftp_sanitycheck Description  Squid performs sanity checks of the addresses of FTP data connections ensure the data connection is to the requested  server Build Option  Default Usage  ftp_sanitycheck on|off  Default  ftp_sanitycheck on Synopsis For security and data integrity reasons Squid by default performs sanity checks of the addresses of FTP data connections ensure the data connection is to the requested  server. If you need to allow FTP connections to servers using another IP address for the data connection then turn this off. Arguments on/off  Enable or disable sanity checks       TAG NAME                   ftp_telnet_protocol Description  Allows to use the telnet protocol as transport channel for the control connection. Build Option  Default Usage  ftp_telnet_protocol on|off  Default  ftp_telnet_protocol on Synopsis The FTP protocol is officially defined to use the telnet protocol as transport channel for the control connection. However, many implementations are broken and does not respect this aspect of the FTP protocol. If there is any trouble accessing files with ASCII code 255 in the path or similar problems involving this ASCII code you can try setting this directive to off. If that helps, report to the operator of the FTP server in question that their FTP server is broken and does not follow the FTP standard. Arguments on/off  Enable or disable telnet protocol as transport channel       TAG NAME                   check_hostnames Description  For security and stability reasons Squid by default checks hostnames for Internet standard RFC compliance Build Option  Default Usage  check_hostnames on|off  Default  check_hostnames on  Synopsis If you want Squid not to perform these checks then turn this directive off. If this directive is set to off, then squid disable the hostname validity/sanity checks before trying to look them up in DNS. Arguments on/off  Enable or disable hostname checks       TAG NAME                   allow_underscore Description  If it is enabled, the underscore character is allowed in the Internet Hostnames Build Option  Default Usage  allow_underscore on|off  Default  allow_underscore on  Synopsis Underscore character is strictly not allowed in Internet hostnames but nevertheless used by many sites. Set this to off if Squid sould be strict about the standard. Arguments on/off  Enable or disable underscore checks in URL       TAG NAME                  cache_dns_program Description  This helper program is used for DNS resolution Build Option  --disable-internal-dns Usage  cache_dns_program program Default  cache_dns_program /usr/local/Squid/libexec/dnsserver  Synopsis Squid requires a non-blocking resolver for its queries, an external program called dnsserver is included in the standard distribution. This tag is used to specify the path for the external dnsserver program. Arguments program  Path and the external dnsserver program Example(s) cache_dns_program /usr/local/libexec/dnsserver       TAG NAME                   dns_children Description  The number of processes spawn to service DNS name lookups Build Option  Default Usage  dns_children number (1 to 32) Default  dns_children 5 Synopsis Specifies the number of external DNS resolver processes that will be started in order to serve requests. The default value of five is enough for many networks, however, if your Squid serves a large number of users, this value may need to be increased to avoid errors. However, increasing the number of processes also increases the load on system resources and may actually hinder performance if set too high. More than 10 is probably overkill. Arguments number  Number of dns children program Example(s) dns_children 10       TAG NAME                   dns_retransmit_interval Description  Defines the initial retransmit time interval for DNS queries Build Option  Default Usage  dns_retransmit_interval time-units Default  dns_retransmit_interval 5 seconds  Synopsis The interval is doubled each time all configured DNS servers have been tried. Arguments time-units  Retransmit time interval Example(s) dns_retransmit_interval 15 seconds       TAG NAME                   dns_timeout Description  This defines the DNS query timeout Build Option  Default Usage  dns_timeout time-units Default  dns_timeout 5 minutes  Synopsis If no response is received to a DNS query within this time then all DNS servers for the queried domain is assumed to be unavailable. Arguments time-units  DNS timeout period Example(s) dns_timeout 10 minutes       TAG NAME                   dns_defnames Description  Enable/disable the dnsserver to add the local domain name to single component host names Build Option  Default Usage  dns_defnames on|off Default  dns_defnames off  Synopsis Normally the 'dnsserver' disables the RES_DEFNAMES resolver option (see res_init(3)).  This prevents caches in a hierarchy from interpreting single-component  hostnames locally.  To allow dnsserver to handle single-component names, enable this option. Arguments on/off  Enable or disable this option       TAG NAME                   dns_nameservers Description  Use this if you want to specify a list of DNS name servers (IP addresses) to use Build Option  Default Usage  dns_nameservers ip_address Default  none  Synopsis Normally defaults to resolve.conf, which simply means that Squid's parent DNS servers will be drawn from the /etc/resolve.conf file found on the system Squid runs on. It is possible to select other DNS servers if needed, for example to choose a more local caching DNS server, or a remote internet connected server. Arguments ip_address  IP address of the dns servers Example(s) dns_nameservers 10.0.0.1 192.172.0.4       TAG NAME                   hosts_file Description  Defines the location of the host-local IP name-address associations database Build Option  Default Usage  host_file path/filename Default  hosts_file /etc/hosts  Synopsis For Unix and Linux system this file is located at /etc/hosts Arguments path  Path to the file that contains the ip addresses filename  File that contains the ip addresses Example(s) hosts_file /hosts       TAG NAME                  diskd_program Description  Specifies the location of the diskd executable Build Option  Default Usage  diskd_program path/filename Default  diskd_program /usr/local/Squid/libexec/diskd  Synopsis This tag is used to specify the location where diskd program is located Note: This is only useful if you have compiled in diskd as one of the store io modules. Arguments path  Path where diskd program is located filename  File that performs diskd operation Example(s) diskd_program /usr/local/libexec/diskd       TAG NAME                  unlinkd_program Description  Specifies the location where executable for file deletion process is stored Build Option  Default Usage  unlinkd_program path/filename Default  unlinkd_program /usr/local/Squid/libexec/unlinkd  Synopsis The name of the helper program that deletes, or unlinks old files in the cache to make room for newer objects. Arguments path  Path where the program is located filename  File that performs the specified operation Example(s) unlinkd_program /usr/local/libexec/unlinkd       TAG NAME                  pinger_program Description  Specifies the location of the executable for the pinger process Build Option  --enable-icmp Usage  pinger_program path/filename Default  pinger_program /usr/local/Squid/libexec/pinger  Synopsis An external program that provides Squid with ICMP RTT information so that it can more effectively choose between multiple remote parent caches for request fulfillment. Arguments path  Path of the pinger executable program filename  File that performs the pinger process Example(s) pinger_program /usr/local/libexec/pinger       TAG NAME                  url_rewrite_program [previously called as redirect_program] Description  Specifies the location of the executable for the URL redirector Build Option  Default Usage  url_rewrite_program path/to/rewriter/program Default  none  Synopsis Specify the location of the executable for the URL rewriter. Since they can perform almost any function there isn't one included. For each requested URL, the rewriter will receive a line input with the following format URL <SP> client_ip "/" fqdn <SP> user <SP> method <SP> urlgroup <NL> The rewriter may return a rewritten URL. The other components of the request line does not need to be returned (ignored if they are). The rewriter can also indicate that a client-side redirect should be performed to the new URL. This is done by prefixing the returned URL with "301:" (moved permanently) or 302: (moved temporarily). It can also return a "urlgroup" that can subsequently be matched in cache_peer_access and similar ACL driven rules. An urlgroup is returned by prefixing the returned url with "!urlgroup!" By default, a URL rewriter is not used. Arguments path  Location of the rewriter program rewriter  Executable file that performs the rewrite process Example(s) url_rewrite_program /usr/local/squirm/bin/squirm       TAG NAME                  url_rewrite_children [previously called as redirect_children]  Description  The number of redirector processes to spawn. Build Option  Default Usage  url_rewrite_children number Default  url_rewrite_children 5             Synopsis The number of redirector processes to spawn. If you start too few Squid will have to wait for them to process a backlog of URLs, slowing it down. If you start too many they will use RAM and other system resources. Aguments number  Number of rewrite process to spawn Example(s) url_rewrite_children 15       TAG NAME                  url_rewrite_concurrency  Description  The number of requests each redirector helper can handle in parallel. Build Option  Default Usage  url_rewrite_concurrency number Default  url_rewrite_concurrency 0  Synopsis The number of requests each redirector helper can handle in parallel. Defaults to 0 which indicates that the redirector is a old-style singlethreaded redirector. Arguments number  Number of requests to be handle Example(s) url_rewrite_concurrency 10       TAG NAME                  url_rewrite_host_header [previously called as redirect_rewrites_host_header] Description  Enable/disable Squid rewriting any host header in redirected requests Build Option  Default Usage  url_rewrite_host_header on|off Default  url_rewrite_host_header on