Metalink

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Metalink

Filename extension	.metalink
Internet media type	application/metalink+xml
Type of format	File distribution
Extended from	XML

Metalink is a cross-platform and cross-application open standard/framework/file format for programs that download, including download managers, BitTorrent clients, Web browsers, FTP clients, and P2P programs. For increased convenience, it stores the multiple download locations for a file (FTP/HTTP/P2P) in a single metafile with the extension .metalink. This provides 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).

Other features include automatic checksum verification of finished downloads, automatic repair of downloads with errors, listing multiple files to be added to a download queue, and automatic OS/language selection.

Metalink is extensible, and supports listing multiple partial and full file hashes/checksums along with PGP signatures. Most clients only support verifying MD5, SHA-1, & SHA-256, however. Besides FTP and HTTP mirror locations and rsync, it also supports listing the P2P methods BitTorrent, ed2k, and magnet link.

Client programs

• aria2 (GPL) is a Unix/Windows command line "high speed download utility" that supports BitTorrent and Metalink (HTTP/FTP/BitTorrent).
• DownThemAll (GPL), a Firefox extension and download manager that has basic Metalink support.
• FlashGot (GPL), a Firefox extension for integrating with many Download Managers, supports Metalink.
• Free Download Manager (GPL), a Windows Download Manager, supports Metalink (HTTP/FTP) in version 2.5.
• GetRight 6, a Windows Download Manager, supports Metalink (HTTP/FTP/BitTorrent).
• GGet (GPL) is a modern download manager for GNOME, with Metalink support via Metalink Checker.
• KGet (GPL), KDE's native download manager, supports Metalink in KDE 4.
• libmetalink (MIT License) is a Metalink library written in C language. It is intended to add Metalink functionality, such as parsing Metalink XML files, to programs written in C.
• Metadl (LGPL) is a NSIS download plugin based on cURL that supports Metalink and downloads from one URL, supports download resume, and verifies checksums. Metadl is used by Wubi, the Windows-based Ubuntu installer.
• Metalink Checker (GPL) is a cross platform command line downloader written in Python that supports multi-source downloads, as well as checking mirrors listed in .metalinks.
• Mini Downloader is a stand alone downloader in a small Windows .exe that downloads Metalinks.
• Offline Explorer is a program that allows you to download an unlimited number of your favorite Web and FTP sites for later offline viewing, editing or browsing.
• Orbit Downloader, a Windows Download Manager, supports Metalink (HTTP/FTP).
• Net Transport, a Windows Download Manager, supports Metalink.
• Phex (GPL), a Mac/Unix/Windows Gnutella client, supports Metalink downloads along with exporting a library to Metalink for sharing between users.
• Retriever is a cross platform Java download manager that supports Metalink and BitTorrent.
• SmartFTP, a Windows GUI FTP client, supports Metalink for adding files to an FTP transfer queue and checksum verification (does not supported segmented downloads).
• Speed Download, a Mac Download Manager, supports Metalink (HTTP/FTP) as of version 4.1.0.
• TheWorld Browser is a Web Browser on Windows that has built-in Metalink (HTTP/FTP) support.
• VeryCD easyMule (GPL) is a version of eMule with Metalink support.
• wxDownload Fast (GPL) is a Mac/Unix/Windows download manager that supports Metalink (HTTP/FTP).

See Comparison of download managers or below for details on which of them support Metalink and have other features.

In use

Mandriva Linux has integrated Metalink into package management with urpmi 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."

Metalink is also being tested with Arch Linux's Pacman which is used for package management.

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.

The following distributions use Metalink for ISO image distribution: 64 Studio, Adios, Arch Linux, Bayanihan Linux, BeleniX, Berry Linux, BLAG Linux and GNU, Bluewhite64 Linux, Damn Small Linux, DesktopBSD, GoboLinux, Granular Linux, KateOS, Linux Mint, MidnightBSD, openSUSE, PC-BSD, Pardus Linux, PCLinuxOS, PuppyLinux, redWall Firewall, Sabayon Linux, StartCom Enterprise Linux, SUSE Linux, TrueBSD, Ubuntu, Ubuntu Christian Edition.

Metalink client feature comparison

A guide to which client support which Metalink features:

No clients support rsync at this time.

Metalink generation

Metalink is XML so they can be hand crafted or XML tools can be used for automation. These tools are specifically for Metalink.

• Bouncer is "database driven mirror management app that has three main components - a bounce script, a sentry script to check mirrors and files for integrity and a set of web-based administration tools." Bouncer supports Metalink via a patch that has not yet been integrated upstream.
• Geo McFly (GPL) is an on the fly generator of metalinks based on the downloader's geographical location, written in Python.
• Metalink Editor (GPL) is a Cross Platform GUI Metalink editor written in Python which allows you to create and edit Metalinks.
• Metalink Library (GPL) is a Cross Platform Metalink library for Python and PHP based on Metalink Editor with many automatic features and an easy command-line interface to generate Metalink and Torrent files.
• Metalink Generator can also be used to create Metalinks by filling out a Web form.
• Metalink tools (GPL) Unix/Windows command line tools for generating Metalinks with checksums and mirror/p2p lists.

• Metamirrors Metagenerate provides an easy to use Web UI to create Metalinks.
• MirrorManager (MIT X11 License) is used by the Fedora Project for dynamically listing mirrors.
• The MirrorBrain (GPL, Apache License) is a real-time Metalink generator and download redirector. It can either return Metalinks, or automatically redirect non-Metalink clients (per HTTP redirection) to a mirror server near them. Advanced features, as transparent negotiation of Metalinks, or embedding of PGP signatures, are fully supported. It is used by openSUSE.

• Origo is a new and easy to use software development and hosting platform for open and closed source projects. Among many features, it has easy release management and mirroring with automatic metalink generation.
• RoPkg::Metalink / Metalink @ Packages Resources (GPL) for automated Metalink generation.
• Simba (GPL), the mirroring tool, includes automatic Metalink generation as one of its features.

Example .metalink file

.metalink is an XML text file.

 <?xml version="1.0" encoding="UTF-8"?>
 <metalink version="3.0" xmlns="http://www.metalinker.org">
   <files>
     <file name="example.ext">
       <verification>
         <hash type="md5">example-md5-hash</hash>
         <hash type="sha1">example-sha1-hash</hash>
         <signature type="pgp"/>
       </verification>
       <resources>
         <url type="ftp" location="us" preference="90">ftp://ftp.example.com/example.ext</url>
         <url type="ftp" location="uk" preference="90">ftp://ftp.example.net/example.ext</url>
         <url type="http" location="us" preference="90">http://example.com/example.ext</url> 
         <url type="http" location="de" preference="90">http://example.net/example.ext</url>
         <url type="bittorrent" preference="100">http://example.org/example.ext.torrent</url>
         <url type="rsync"/>
         <url type="magnet"/>
         <url type="ed2k"/>
       </resources>
     </file>
   </files>
 </metalink>

External links

• Metalink homepage
• Metalink 3.0 Specification
• Making Metalinks.