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Filename extension | .meta4, .metalink |
---|---|
Internet media type |
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Type of format | File distribution |
Extended from | XML, HTTP |
Standard | RFC 5854, RFC 6249 |
Metalink is an extensible metadata file format that describes one or more computer files available for download. It specifies files appropriate for the user's language and operating system; facilitates file verification and recovery from data corruption; and lists alternate download sources (mirror URIs).
The metadata is encoded in HTTP header fields and/or in an XML file with extension .meta4 or .metalink. The duplicate download locations provide reliability in case one method fails. Some clients also achieve faster download speeds by allowing different chunks/segments of each file to be downloaded from multiple resources at the same time (segmented downloading).
Metalink supports listing multiple partial and full file hashes along with PGP signatures. Most clients only support verifying MD5, SHA-1, and SHA-256, however. Besides FTP and HTTP mirror locations and rsync, it also supports listing the P2P methods BitTorrent, ed2k, magnet link or any other that uses a URI.
Metalink 3.0 was publicly released in 2005. It was designed to aid in downloading Linux ISO images and other large files on release day, when servers would be overloaded (each server would have to be tried manually) and to repair large downloads by replacing only the parts with errors instead of fully re-downloading them. It was initially adopted by download managers, and was used by open source projects such as OpenOffice.org and Linux distributions. A community developed around it, more download programs supported it (including proprietary ones) and it saw commercial adoption. In 2008, the community took their work to the Internet Engineering Task Force which resulted in Metalink 4.0 in 2010, described in a Standards Track RFC. [1] Metalink 3.0 (with the extension .metalink) and Metalink 4.0 (with the extension .meta4) are incompatible because they have a slightly different format. In 2011, another Standards Track RFC described Metalink in HTTP header fields. [2]
This section needs additional citations for verification .(October 2016) |
Tool | Debian-based | Fedora-based | Arch-based | BSD-based | Windows |
---|---|---|---|---|---|
aria2 [3] | Yes | Yes | Yes [4] | Yes [5] | |
cURL | No; built without Metalink support | No; built without Metalink support | |||
Wget | Yes; v1.17 or later built with metalink support | Yes; v1.17 or later built with metalink support | Yes; v1.17 or later built with metalink support | Yes; v1.17 or later built with metalink support | |
DownThemAll | not in repo | not in repo | not in repo | not in repo | |
FlashGot | not in repo | not in repo | not in repo | not in repo | |
Free Download Manager | not in repo | not in repo | not in repo | not in repo | |
GetRight | not in repo | not in repo | not in repo | not in repo | |
jDownloader | not in repo | not in repo | not in repo | not in repo | |
KGet | Yes | Yes | Yes | Yes | No |
Phex | not in repo | not in repo | not in repo | not in repo | |
SmartFTP | not in repo | not in repo | not in repo | not in repo | |
easyMule | not in repo | not in repo | not in repo | not in repo | |
ZYpp | not in repo | not in repo | not in repo | not in repo | |
Mandriva Linux has integrated Metalink into package management with urpmi and aria2. Fedora has integrated Metalink into package management with yum. openSUSE has integrated Metalink into package management with ZYpp and aria2.
Wubi, the Windows-based Ubuntu installer, uses Metadl (LGPL) to download Ubuntu ISO images and takes advantage of Metalink's features of higher availability and increased reliability. If there are errors in the download, they are repaired, instead of restarting the large download.
Appupdater (GPL) for Windows "is similar to apt-get or yum on Linux. It automates the process of installing and maintaining up to date versions of programs."[ citation needed ]
Currently, OpenOffice.org uses Metalinks to distribute their free office suite. cURL offers Metalinks of their downloads. UniProt Consortium also provides a Metalink for their large protein database. Dofus, a Flash MMORPG uses Metalinks for downloads and so does SageMath, the open-source mathematical software.
According to the main metalinker.org site, the software hosting and collaboration platform Origo generates Metalinks for all hosted releases. [6]
The following Linux distributions use Metalink for ISO image distribution:[ citation needed ] Adios, Bayanihan Linux, BeleniX, Berry Linux, BLAG Linux and GNU, Bluewhite64 Linux, Damn Small Linux, Fedora, GoboLinux, Granular Linux, KateOS, Linux Mint, openSUSE, Pardus Linux, PCLinuxOS, PuppyLinux, Sabayon Linux, StartCom Enterprise Linux, SUSE Linux, Ubuntu.
The following FreeBSD based distributions use Metalink for ISO image distribution: DesktopBSD, MidnightBSD, and TrueOS.
A guide to which clients support which Metalink features:
Client | wget | cURL | DownThemAll | Free Download Manager | GetRight | KGet | Phex | SmartFTP |
---|---|---|---|---|---|---|---|---|
Licensing | Free Software (GNU General Public License) | Free Software (MIT/X derivate license) | Free Software (GNU General Public License) | Free Software (GNU General Public License) | Proprietary / $29.95 for Standard, $49.95 for Pro | Free Software (GNU General Public License) | Free Software (GNU General Public License) | Proprietary / Free 30 day Evaluation Multiple Editions/$39.99 Professional |
Interface | CLI | CLI | GUI | GUI | GUI | GUI | GUI | GUI |
Metalink 4.0 | Yes | Yes | Yes | No | No | Yes | No | Yes |
Runs on Linux | Yes | Yes | Yes | No | No | Yes | Yes | No |
Runs on Windows | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes |
Runs on Mac OS X | Yes | Yes | Yes | No | No | No | Yes | No |
Resume Downloads | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes [7] |
Segmented Downloads | ? | ? | Yes | Yes | Yes | Yes | Yes | No |
Multiple File support | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes |
"location" | ? | ? | Yes | No | No | No | No | No |
OS | ? | ? | Yes | Yes | No | No | No | No |
Language | ? | ? | Yes | No | No | No | No | No |
HTTP with Transparent Negotiation | ? | ? | Yes | No | No | No | No | No |
Metalink/HTTP | ? | ? | No | No | No | No | No | No |
HTTP | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
FTP | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
BitTorrent | ? | No | Yes | Yes | Yes | No | No | |
magnet | ? | ? | No | No | No | No | Yes | No |
MD5 Hashes | ? | Yes | Yes | Yes | Yes | Yes | Yes | |
SHA-1 Hashes | ? | Yes | Yes | Yes | Yes | Yes | Yes | |
SHA-256 Hashes | ? | Yes | Yes | No | No | No | Yes | |
Piece Hashes | ? | ? | No | No | No | No | No | No |
PGP Signatures | ? | ? | No | No | No | No | No | No |
No clients support rsync at this time.
Metalink is formatted as XML so it can be either hand-crafted or created with an XML library, useful for automation. These tools are specifically for Metalink.
Metalink 4.0 files have the extension .meta4 and are XML text files. They are served with the application/metalink4+xml Internet media type.
<?xml version="1.0" encoding="UTF-8"?><metalinkxmlns="urn:ietf:params:xml:ns:metalink"><published>2009-05-15T12:23:23Z</published><filename="example.ext"><size>14471447</size><identity>Example</identity><version>1.0</version><language>en</language><description>Adescriptionoftheexamplefilefordownload. </description><hashtype="sha-256">3d6fece8033d146d8611eab4f032df738c8c1283620fd02a1f2bfec6e27d590d</hash><urllocation="de"priority="1">ftp://ftp.example.com/example.ext</url><urllocation="fr"priority="1">http://example.com/example.ext</url><metaurlmediatype="torrent"priority="2">http://example.com/example.ext.torrent</metaurl></file></metalink>
Metalink in HTTP header fields makes use of existing standard HTTP header fields such as ETags, Link header fields (for mirrors and P2P), and Instance Digests (for hashes).
Etag: "thvDyvhfIqlvFe+A9MYgxAfm1q5=" Link: <http://www2.example.com/example.ext>; rel=duplicate Link: <ftp://ftp.example.com/example.ext>; rel=duplicate Link: <http://example.com/example.ext.torrent>; rel=describedby; type="application/x-bittorrent" Link: <http://example.com/example.ext.meta4>; rel=describedby; type="application/metalink4+xml" Link: <http://example.com/example.ext.asc>; rel=describedby; type="application/pgp-signature" Digest: SHA-256=MWVkMWQxYTRiMzk5MDQ0MzI3NGU5NDEyZTk5OWY1ZGFmNzgyZTJlODYzYjRjYzFhOTlmNTQwYzI2M2QwM2U2MQ==
Metalink 3.0 files have the extension .metalink and are XML text files.
<?xml version="1.0" encoding="UTF-8"?><metalinkversion="3.0"xmlns="http://www.metalinker.org/"><files><filename="example.ext"><verification><hashtype="md5">example-md5-hash</hash><hashtype="sha1">example-sha1-hash</hash><signaturetype="pgp"/></verification><resources><urltype="ftp"location="us"preference="90">ftp://ftp.example.com/example.ext</url><urltype="ftp"location="uk"preference="90">ftp://ftp.example.net/example.ext</url><urltype="http"location="us"preference="90">http://example.com/example.ext</url><urltype="http"location="de"preference="90">http://example.net/example.ext</url><urltype="bittorrent"preference="100">http://example.org/example.ext.torrent</url><urltype="rsync"/><urltype="magnet"/><urltype="ed2k"/></resources></file></files></metalink>
Konqueror is a free and open-source web browser and file manager that provides web access and file-viewer functionality for file systems. It forms a core part of the KDE Software Compilation. Developed by volunteers, Konqueror can run on most Unix-like operating systems. The KDE community licenses and distributes Konqueror under GNU GPL-2.0-or-later.
Shareaza is a peer-to-peer file sharing client running under Microsoft Windows which supports the Gnutella, Gnutella2 (G2), eDonkey, BitTorrent, FTP, HTTP and HTTPS network protocols and handles magnet links, ed2k links, and the now deprecated gnutella and Piolet links. It is available in 30 languages.
eDonkey2000 was a peer-to-peer file sharing application developed by US company MetaMachine, using the Multisource File Transfer Protocol. It supported both the eDonkey2000 network and the Overnet network.
rsync is a utility for transferring and synchronizing files between a computer and a storage drive and across networked computers by comparing the modification times and sizes of files. It is commonly found on Unix-like operating systems and is under the GPL-3.0-or-later license.
Squid is a caching and forwarding HTTP web proxy. It has a wide variety of uses, including speeding up a web server by caching repeated requests, caching World Wide Web (WWW), Domain Name System (DNS), and other network lookups for a group of people sharing network resources, and aiding security by filtering traffic. Although used for mainly HTTP and File Transfer Protocol (FTP), Squid includes limited support for several other protocols including Internet Gopher, Secure Sockets Layer (SSL), Transport Layer Security (TLS), and Hypertext Transfer Protocol Secure (HTTPS). Squid does not support the SOCKS protocol, unlike Privoxy, with which Squid can be used in order to provide SOCKS support.
BitTorrent, also referred to simply as torrent, is a communication protocol for peer-to-peer file sharing (P2P), which enables users to distribute data and electronic files over the Internet in a decentralized manner. The protocol is developed and maintained by Rainberry, Inc., and was first released in 2001.
GNU Wget is a computer program that retrieves content from web servers. It is part of the GNU Project. Its name derives from "World Wide Web" and "get". It supports downloading via HTTP, HTTPS, and FTP.
BitComet is a cross-protocol BitTorrent, HTTP and FTP client written in C++ for Microsoft Windows and available in 52 different languages. Its first public release was version 0.28. The current BitComet logo has been used since version 0.50.
FileZilla is a free and open-source, cross-platform FTP application, consisting of FileZilla Client and FileZilla Server. Clients are available for Windows, Linux, and macOS. Both server and client support FTP and FTPS, while the client can in addition connect to SFTP servers. FileZilla's source code is hosted on SourceForge.
Magnet is a URI scheme that defines the format of magnet links, a de facto standard for identifying files (URN) by their content, via cryptographic hash value rather than by their location.
In computer hypertext, a URI fragment is a string of characters that refers to a resource that is subordinate to another, primary resource. The primary resource is identified by a Uniform Resource Identifier (URI), and the fragment identifier points to the subordinate resource.
Gajim is an instant messaging client for the XMPP protocol which uses the GTK toolkit. The name Gajim is a recursive acronym for Gajim's a jabber instant messenger. Gajim runs on Linux, BSD, macOS, and Microsoft Windows. Released under the GPL-3.0-only license, Gajim is free software. A 2009 round-up of similar software on Tom's Hardware found version 0.12.1 "the lightest and fastest jabber IM client".
BitTorrent is a proprietary adware BitTorrent client developed by Bram Cohen and Rainberry, Inc. used for uploading and downloading files via the BitTorrent protocol. BitTorrent was the first client written for the protocol. It is often nicknamed Mainline by developers denoting its official origins. Since version 6.0 the BitTorrent client has been a rebranded version of μTorrent. As a result, it is no longer open source. It is currently available for Microsoft Windows, Mac, Linux, iOS and Android. There are currently two versions of the software, "BitTorrent Classic" which inherits the historical version numbering, and "BitTorrent Web", which uses its own version numbering.
In computing, Java Web Start is a deprecated framework developed by Sun Microsystems that allows users to start application software for the Java Platform directly from the Internet using a web browser. The technology enables seamless version updating for globally distributed applications and greater control of memory allocation to the Java virtual machine.
Free Download Manager is a download manager for Windows, macOS, Linux and Android.
The following is a general comparison of BitTorrent clients, which are computer programs designed for peer-to-peer file sharing using the BitTorrent protocol.
CrushFTP is a proprietary multi-protocol, multi-platform file transfer server originally developed in 1999. CrushFTP is shareware with a tiered pricing model. It is targeted at home users on up to enterprise users.
Lphant was a peer-to-peer file sharing client for the Microsoft Windows, Linux and Mac OS operating systems, which supports the eDonkey Network and the BitTorrent protocol. It was available in 19 languages. The name and logo of the original Lphant application has been replicated in a program called "Lphant 6.0".
In the BitTorrent file distribution system, a torrent file or meta-info file is a computer file that contains metadata about files and folders to be distributed, and usually also a list of the network locations of trackers, which are computers that help participants in the system find each other and form efficient distribution groups called swarms. Torrent files are normally named with the extension .torrent
.
Mirror sites or mirrors are replicas of other websites. The concept of mirroring applies to network services accessible through any protocol, such as HTTP or FTP. Such sites have different URLs than the original site, but host identical or near-identical content. Mirror sites are often located in a different geographic region than the original, or upstream site. The purpose of mirrors is to reduce network traffic, improve access speed, ensure availability of the original site for technical or political reasons, or provide a real-time backup of the original site. Mirror sites are particularly important in developing countries, where internet access may be slower or less reliable.