<?xml version="1.0" encoding="utf-8" standalone="no"?> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [ <!ENTITY % aptent SYSTEM "apt.ent"> %aptent; <!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent"> %aptverbatiment; <!ENTITY % aptvendor SYSTEM "apt-vendor.ent"> %aptvendor; ]> <refentry> <refentryinfo> &apt-author.team; &apt-email; &apt-product; <!-- The last update date --> <date>2017-11-22T00:00:00Z</date> </refentryinfo> <refmeta> <refentrytitle>apt-transport-http</refentrytitle> <manvolnum>1</manvolnum> <refmiscinfo class="manual">APT</refmiscinfo> </refmeta> <!-- Man page title --> <refnamediv> <refname>apt-transport-http</refname> <refpurpose>APT transport for downloading via the Hypertext Transfer Protocol (HTTP)</refpurpose> </refnamediv> <refsect1><title>Description</title> <para>This APT transport allows the use of repositories accessed via the Hypertext Transfer Protocol (HTTP). It is available by default and probably the most used of all transports. Note that a transport is never called directly by a user but used by APT tools based on user configuration.</para> <para>HTTP is an unencrypted transport protocol meaning that the whole communication with the remote server (or proxy) can be observed by a sufficiently capable attacker commonly referred to as a "man in the middle" (MITM). However, such an attacker can <emphasis>not</emphasis> modify the communication to compromise the security of your system, as APT's data security model is independent of the chosen transport method. This is explained in detail in &apt-secure;. An overview of available transport methods is given in &sources-list;.</para> </refsect1> <refsect1><title>Options</title> <para>Various options can be set in an &apt-conf; file to modify its behavior, ranging from proxy configuration to workarounds for specific server limitations.</para> <refsect2><title>Proxy Configuration</title> <para>The environment variable <envar>http_proxy</envar> is supported for system wide configuration. Proxies specific to APT can be configured via the option <literal>Acquire::http::Proxy</literal>. Proxies which should be used only for certain hosts can be specified via <literal>Acquire::http::Proxy::<replaceable>host</replaceable></literal>. Even more finegrained control can be achieved via proxy autodetection, detailed further below. All these options use the URI format <literal><replaceable>scheme</replaceable>://[[<replaceable>user</replaceable>][:<replaceable>pass</replaceable>]@]<replaceable>host</replaceable>[:<replaceable>port</replaceable>]/</literal>. Supported URI schemes are <literal>socks5h</literal> (SOCKS5 with remote DNS resolution), <literal>http</literal> and <literal>https</literal>. Authentication details can be supplied via &apt-authconf; instead of including it in the URI directly.</para> <para>The various APT configuration options support the special value <literal>DIRECT</literal> meaning that no proxy should be used. The environment variable <envar>no_proxy</envar> is also supported for the same purpose.</para> <para>Furthermore, there are three settings provided for cache control with HTTP/1.1 compliant proxy caches: <literal>Acquire::http::No-Cache</literal> tells the proxy not to use its cached response under any circumstances. <literal>Acquire::http::Max-Age</literal> sets the allowed maximum age (in seconds) of an index file in the cache of the proxy. <literal>Acquire::http::No-Store</literal> specifies that the proxy should not store the requested archive files in its cache, which can be used to prevent the proxy from polluting its cache with (big) .deb files.</para> </refsect2> <refsect2><title>Automatic Proxy Configuration</title> <para><literal>Acquire::http::Proxy-Auto-Detect</literal> can be used to specify an external command to discover the HTTP proxy to use. The first and only parameter is a URI denoting the host to be contacted, to allow for host-specific configuration. APT expects the command to output the proxy on stdout as a single line in the previously specified URI format or the word <literal>DIRECT</literal> if no proxy should be used. No output indicates that the generic proxy settings should be used.</para> <para>Note that auto-detection will not be used for a host if a host-specific proxy configuration is already set via <literal>Acquire::http::Proxy::<replaceable>host</replaceable></literal>.</para> <para>See the &squid-deb-proxy-client; and &auto-apt-proxy; packages for example implementations.</para> <para>This option takes precedence over the legacy option name <literal>Acquire::http::ProxyAutoDetect</literal>.</para> </refsect2> <refsect2><title>Connection Configuration</title> <para>The option <literal>Acquire::http::Timeout</literal> sets the timeout timer used by the method; this value applies to the connection as well as the data timeout.</para> <para>The used bandwidth can be limited with <literal>Acquire::http::Dl-Limit</literal> which accepts integer values in kilobytes per second. The default value is 0 which deactivates the limit and tries to use all available bandwidth. Note that this option implicitly disables downloading from multiple servers at the same time.</para> <para>The setting <literal>Acquire::http::Pipeline-Depth</literal> can be used to enable HTTP pipelining (RFC 2616 section 8.1.2.2) which can be beneficial e.g. on high-latency connections. It specifies how many requests are sent in a pipeline. APT tries to detect and work around misbehaving webservers and proxies at runtime, but if you know that yours does not conform to the HTTP/1.1 specification, pipelining can be disabled by setting the value to 0. It is enabled by default with the value 10.</para> <para><literal>Acquire::http::AllowRedirect</literal> controls whether APT will follow redirects, which is enabled by default.</para> <para><literal>Acquire::http::User-Agent</literal> can be used to set a different User-Agent for the http download method as some proxies allow access for clients only if the client uses a known identifier.</para> <para><literal>Acquire::http::SendAccept</literal> is enabled by default and sends an <literal>Accept: text/*</literal> header field to the server for requests without file extensions to prevent the server from attempting content negotiation.</para> </refsect2> </refsect1> <refsect1><title>Examples</title> <literallayout> Acquire::http { Proxy::example.org "DIRECT"; Proxy "socks5h://apt:pass@127.0.0.1:9050"; Proxy-Auto-Detect "/usr/local/bin/apt-http-proxy-auto-detect"; No-Cache "true"; Max-Age "3600"; No-Store "true"; Timeout "10"; Dl-Limit "42"; Pipeline-Depth "0"; AllowRedirect "false"; User-Agent "My APT-HTTP"; SendAccept "false"; }; </literallayout> </refsect1> <refsect1> <title>See Also</title> <para>&apt-conf; &apt-authconf; &sources-list; </para> </refsect1> &manbugs; </refentry>