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Unison is a multi-platform file-synchronization tool. It stores two replicas of a collection of files and directories on different hosts (or different disks on the same host), can modify them separately, and then updates them by propagating the changes in each replica to the other. NON-conflicting updates are propagated automatically; conflicting updates are detected and displayed. Unison can deal with updates to both replicas of a distributed directory structure. It works across platforms, and is a user-level program- users do not need superuser privileges on either host. It works between any pair of machines connected to the internet, communicating over either a direct socket link or tunneling over an rsh or an encrypted ssh connection. It conserves bandwidth, and runs well over slow links such as PPP connections. Transfers of small updates to large files are optimized using a compression protocol similar to rsync.


User manual available in HTML format from

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LicenseVerified byVerified onNotes
GPLv2Janet Casey17 July 2003

Leaders and contributors

Benjamin Pierce Maintainer
Matthieu Goulay Contributor
Sylvain Gommier Contributor

Resources and communication

Audience Resource type URI
Developer VCS Repository Webview
Help E-mail
Developer E-mail
Bug Tracking,Support E-mail

Software prerequisites

This entry (in part or in whole) was last reviewed on 11 May 2005.


Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the page “GNU Free Documentation License”.

The copyright and license notices on this page only apply to the text on this page. Any software or copyright-licenses or other similar notices described in this text has its own copyright notice and license, which can usually be found in the distribution or license text itself.

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