View source for Rsync

{{short description|File synchronization protocol and software}}
{{lowercase}}
{{Use dmy dates|date=July 2020}}
{{Infobox software
| name                   = rsync
| logo                   = Newrsynclogo.png
| screenshot             = <!-- [[File: ]] -->
| caption                = rsync logo
| collapsible            =
| author                 = [[Andrew Tridgell]], [[Paul Mackerras]]<ref name="rsyncrel" />
| developer              = Wayne Davison<ref name="rsync-website" />
| released               = {{Start date and age|1996|06|19}}<ref name="rsyncrel">{{Cite newsgroup |url=http://groups.google.com/group/comp.os.linux.announce/msg/3bb93f6484065f20 |title=First release of rsync – rcp replacement |last=Tridgell |first=Andrew |date=19 June 1996 |newsgroup=comp.os.linux.announce |message-id=cola-liw-835153950-21793-0@liw.clinet.fi |archive-url=https://web.archive.org/web/20111108064132/http://groups.google.com/group/comp.os.linux.announce/msg/3bb93f6484065f20 |archive-date=8 November 2011 |access-date=19 July 2007 |url-status=live}}</ref>
| discontinued           =
| latest release version = {{wikidata|property|preferred|reference|edit|Q283774|P348|P548=Q2804309}}
| latest release date    = {{start date and age|{{wikidata|qualifier|Q283774|P348|P548=Q2804309|P577}}}}
| latest preview version = {{wikidata|property|preferred|reference|edit|Q283774|P348|P548=Q51930650}}
| latest preview date    = {{start date and age|{{wikidata|qualifier|Q283774|P348|P548=Q51930650|P577}}}}
| programming language   = [[C (programming language)|C]]
| operating system       =
| platform               = [[Cross-platform software|Cross-platform]]
| size                   =
| genre                  = [[Data transfer]], [[differential backup]]
| license                = 2007: [[GNU General Public License|GPL-3.0-or-later]]{{efn|GPL-3.0-or-later since 2007-07-10, pre-release 3.0.0pre1 on 2007-10-05, stable 3.0.0 on 2008-03-01.}}<ref name="NEWS">{{cite web|url=https://download.samba.org/pub/rsync/NEWS#3.0.0|title=News}}</ref><ref name="GPL-3.0-or-later">{{cite web|url=https://git.samba.org/rsync.git/?p=rsync.git;a=commitdiff;h=8e41b68e8f975c02a5d9281be780ba5d1a385107|title=tweaking the license text a bit more}}</ref><ref name="GPL.html">{{cite web|url=https://rsync.samba.org/GPL.html|title=rsync's license}}</ref><br />2007: [[GNU General Public License|GPL-3.0-only]]{{efn|GPL-3.0-only from 2007-07-07 until 2007-07-09.}}<br />2007: [[GNU General Public License|GPL-2.0-only]]{{efn|GPL-2.0-only from 2007-02-04 until 2007-07-07.}}<br />1996: [[GNU General Public License|GPL-2.0-or-later]]{{efn|GPL-2.0-or-later from 1996-06-16 until 2007-01-31, versions 0.1 to 2.6.9.}}<ref name="GPL2.html">{{cite web|url=http://rsync.samba.org/GPL2.html|title=rsync's license}}</ref>
| website                = 
}}

'''rsync''' (remote sync) is a utility for [[file transfer|transferring]] and [[file synchronization|synchronizing]] [[computer file|files]] between a computer and a storage drive and across [[computer network|networked]] [[computer]]s by comparing the [[timestamping (computing)|modification times]] and sizes of files.<ref name="man page">{{Cite web |title=rsync(1) – Linux man page |url=https://linux.die.net/man/1/rsync |url-status=live |archive-url=https://web.archive.org/web/20170101060106/https://linux.die.net/man/1/rsync |archive-date=1 January 2017 |access-date=2 February 2017 |website=linux.die.net}}</ref> It is commonly found on [[Unix-like]] [[operating system]]s and is under the [[GNU General Public License|GPL-3.0-or-later]] license.<ref name="NEWS" /><ref name="GPL-3.0-or-later" /><ref name="Sayood">{{Cite book |last=Sayood |first=Khalid |url=https://books.google.com/books?id=Duz1wQEBkb8C&q=rsync+widely+used&pg=PA280 |title=Lossless compression handbook |date=18 December 2002 |publisher=Elsevier |isbn=9780080510491 |access-date=18 August 2014}}</ref><ref>{{Cite book |url=https://archive.org/details/springer_10.1007-1-4020-2258-1 |title=Web content caching and distribution: proceedings of the 8th International Workshop |publisher=Springer Science & Business Media |year=2004 |page=[https://archive.org/details/springer_10.1007-1-4020-2258-1/page/n323 316] |isbn=9781402022579 |quote=rsync widely used. |access-date=18 August 2014 |via=[[Internet Archive]]}}</ref><ref>Rasch, David; Burns, Randal; [http://hssl.cs.jhu.edu/ip-rsync/ip-rsync.pdf ''In-Place Rsync: File Synchronization for Mobile and Wireless Devices''] {{Webarchive|url=https://web.archive.org/web/20160413200016/http://hssl.cs.jhu.edu/ip-rsync/ip-rsync.pdf |date=13 April 2016 }}, Department of Computer Science, Johns Hopkins University</ref><ref>{{Cite journal |last1=Dempsey |first1=Bert J. |last2=Weiss |first2=Debra |date=30 April 1999 |title=Towards an Efficient, Scalable Replication Mechanism for the I2-DSI Project |journal=Technical Report TR-1999-01 |citeseerx=10.1.1.95.5042}}</ref>

rsync is written in [[C (programming language)|C]] as a single-[[Thread (computing)|threaded]] application.<ref>{{Cite web |title=Bash - Speed up rsync with Simultaneous/Concurrent File Transfers? - Stack Overflow |url=https://stackoverflow.com/questions/24058544/speed-up-rsync-with-simultaneous-concurrent-file-transfers |url-status=live |archive-url=https://web.archive.org/web/20190806235906/https://stackoverflow.com/questions/24058544/speed-up-rsync-with-simultaneous-concurrent-file-transfers |archive-date=6 August 2019 |access-date=18 December 2019}}</ref> The rsync algorithm is a type of [[delta encoding]], and is used for minimizing network usage. [[zstd|Zstandard]], [[LZ4 (compression algorithm)|LZ4]], or [[Zlib]] may be used for additional [[data compression]],<ref name="man page" /> and [[Secure Shell|SSH]] or [[stunnel]] can be used for security.

rsync is typically used for synchronizing files and directories between two different systems. For example, if the command <code>rsync local-file user@remote-host:remote-file</code> is run, rsync will use SSH to connect as <code>user</code> to <code>remote-host</code>.<ref>{{Cite web |title=Using Rsync and SSH |url=https://troy.jdmz.net/rsync/index.html |access-date=18 August 2014 |publisher=Troy.jdmz.net}}</ref> Once connected, it will invoke the remote host's rsync and then the two programs will determine what parts of the local file need to be transferred so that the remote file matches the local one.  One application of rsync is the synchronization of [[Software repository|software repositories]] on [[Mirror site|mirror sites]] used by [[Package manager|package management systems]].<ref>{{Cite web |title=Using and running mirrors |url=https://www.gnu.org/server/mirror.html |url-status=live |archive-url=https://web.archive.org/web/20200416235132/https://www.gnu.org/server/mirror.html |archive-date=16 April 2020 |access-date=15 April 2020 |publisher=GNU Project}}</ref><ref>{{Cite web |title=How to create public mirrors for CentOS |url=https://wiki.centos.org/HowTos/CreatePublicMirrors |url-status=live |archive-url=https://web.archive.org/web/20200401031641/https://wiki.centos.org/HowTos/CreatePublicMirrors |archive-date=1 April 2020 |access-date=15 April 2020 |publisher=CentOS wiki}}</ref>

rsync can also operate in a [[Daemon (computing)|daemon]] mode (rsyncd), serving and receiving files in the native rsync protocol (using the <code>rsync://</code> syntax).

== History ==
[[Andrew Tridgell]] and [[Paul Mackerras]] wrote the original rsync, which was first announced on 19 June 1996.<ref name="rsyncrel" /> It is similar in function and invocation to '''rdist''' (<code>rdist -c</code>), created by [[Ralph Campbell (computing)|Ralph Campbell]] in 1983 and released as part of [[4.3BSD]].<ref name="rdistrel">{{Cite web |title=rdist(1) |url=https://man.freebsd.org/cgi/man.cgi?query=rdist&apropos=0&sektion=0&manpath=FreeBSD+1.0-RELEASE&arch=default&format=html}}</ref> Tridgell discusses the design, implementation, and performance of rsync in chapters 3 through 5 of his 1999 [[Doctor of Philosophy|Ph.D.]] thesis.<ref>Tridgell, Andrew; [//rsync.samba.org/~tridge/phd_thesis.pdf ''Efficient Algorithms for Sorting and Synchronization''], February 1999, retrieved 29 September 2009</ref> {{As of|2023||url=https://rsync.samba.org/}}, it is maintained by [[Wayne Davison]].<ref name="rsync-website">{{Cite web |title=rsync |url=http://rsync.samba.org |url-status=live |archive-url=https://web.archive.org/web/20141127111140/http://rsync.samba.org/ |archive-date=27 November 2014 |access-date=28 November 2014}}</ref>

Because of its flexibility, speed, and scriptability, <code>rsync</code> has become a standard Linux utility, included in all popular Linux distributions.{{cn|date=February 2022}} It has been ported to Windows (via [[Cygwin]], [[Grsync]], or [[Windows Services for UNIX|SFU]]<ref>{{Cite web |title=Tool Warehouse |url=http://www.suacommunity.com/tool_warehouse.aspx |archive-url=https://web.archive.org/web/20130406032657/http://www.suacommunity.com/tool_warehouse.aspx |archive-date=6 April 2013 |url-status=usurped |website=SUA Community}}</ref>), [[FreeBSD]],<ref>{{Cite web |title=FreeBSD Ports |url=https://svnweb.freebsd.org/ports/head/net/rsync/pkg-descr?view=markup |access-date=24 October 2016}}</ref> [[NetBSD]],<ref>{{Cite web |title=NetBSD Ports |url=http://ftp.netbsd.org/pub/pkgsrc/current/pkgsrc/net/rsync/README.html |url-status=live |archive-url=https://web.archive.org/web/20161025110838/http://ftp.netbsd.org/pub/pkgsrc/current/pkgsrc/net/rsync/README.html |archive-date=25 October 2016 |access-date=24 October 2016}}</ref> [[OpenBSD]],<ref>{{Cite web |title=OpenBSD Ports |url=http://cvsweb.openbsd.org/cgi-bin/cvsweb/ports/net/rsync/ |access-date=24 October 2016}}</ref> and [[macOS]].

== Use ==
Similar to '''[[cp (Unix)|<code>cp</code>]]''', '''[[rcp (Unix)|<code>rcp</code>]]''' and '''[[Secure copy|<code>scp</code>]]''', '''<code>rsync</code>''' requires the specification of a source and a destination, of which at least one must be local.<ref>See the [http://rsync.samba.org/ftp/rsync/README README file] {{Webarchive|url=https://web.archive.org/web/20071210003559/http://rsync.samba.org/ftp/rsync/README |date=10 December 2007 }}</ref>

Generic syntax:
<syntaxhighlight lang="bash">
rsync [OPTION] … SRC … [USER@]HOST:DEST
rsync [OPTION] … [USER@]HOST:SRC [DEST]
</syntaxhighlight>

where {{var|SRC}} is the file or directory (or a list of multiple files and directories) to copy from, {{var|DEST}} is the file or directory to copy to, and square brackets indicate optional parameters.

<code>rsync</code> can synchronize Unix clients to a central Unix server using <code>rsync</code>/<code>ssh</code> and standard Unix accounts. It can be used in desktop environments, for example to efficiently synchronize files with a backup copy on an external hard drive. A scheduling utility such as <code>[[cron]]</code> can carry out tasks such as automated encrypted <code>rsync</code>-based mirroring between multiple hosts and a central server.

== Examples ==
A command line to mirror [[FreeBSD]] might look like:<ref>{{Cite web |title=How to Mirror FreeBSD (With rsync) |url=http://www.freebsd.org/doc/en/articles/hubs/mirror-howto.html |access-date=18 August 2014 |publisher=Freebsd.org}}</ref>

<syntaxhighlight lang="bash">
$ rsync -avz --delete ftp4.de.FreeBSD.org::FreeBSD/ /pub/FreeBSD/
</syntaxhighlight>

The [[Apache HTTP Server]] supports rsync only for updating mirrors.<ref>{{Cite web |title=How to become a mirror for the Apache Software Foundation |url=http://www.apache.org/info/how-to-mirror.html |url-status=live |archive-url=https://web.archive.org/web/20140821040343/http://www.apache.org/info/how-to-mirror.html |archive-date=21 August 2014 |access-date=18 August 2014 |publisher=Apache.org}}</ref>

<syntaxhighlight lang="bash">
$ rsync -avz --delete --safe-links rsync.apache.org::apache-dist /path/to/mirror
</syntaxhighlight>

The preferred (and simplest) way to mirror a [[PuTTY]] website to the current directory is to use rsync.<ref>{{Cite web |date=20 December 2007 |title=PuTTY Web Site Mirrors: Mirroring guidelines |url=http://www.chiark.greenend.org.uk/~sgtatham/putty/mirrors.html#guidelines |url-status=live |archive-url=https://web.archive.org/web/20140819090430/http://www.chiark.greenend.org.uk/~sgtatham/putty/mirrors.html#guidelines |archive-date=19 August 2014 |access-date=18 August 2014 |publisher=Chiark.greenend.org.uk}}</ref>

<syntaxhighlight lang="bash">
$ rsync -auH rsync://rsync.chiark.greenend.org.uk/ftp/users/sgtatham/putty-website-mirror/ .
</syntaxhighlight>

A way to mimic the capabilities of [[Time Machine (macOS)]];<ref>{{Cite web |title=Rsync set up to run like Time Machine |url=http://blog.interlinked.org/tutorials/rsync_time_machine.html |url-status=live |archive-url=https://web.archive.org/web/20071115224128/http://blog.interlinked.org/tutorials/rsync_time_machine.html |archive-date=15 November 2007 |access-date=18 August 2014 |publisher=Blog.interlinked.org}}</ref>

<syntaxhighlight lang="bash">
$ date=$(date "+%FT%H-%M-%S") # rsync interprets ":" as separator between host and port (i.e. host:port), so we cannot use %T or %H:%M:%S here, so we use %H-%M-%S
$ rsync -aP --link-dest=$HOME/Backups/current /path/to/important_files $HOME/Backups/back-$date
$ ln -nfs $HOME/Backups/back-$date $HOME/Backups/current
</syntaxhighlight>
Make a full backup of system root directory:<ref>{{Cite web |title=Full system backup with rsync |url=https://wiki.archlinux.org/index.php/Full_system_backup_with_rsync |url-status=live |archive-url=https://web.archive.org/web/20150211163817/https://wiki.archlinux.org/index.php/Full_System_Backup_with_rsync |archive-date=11 February 2015 |access-date=15 December 2014 |publisher=wiki.archlinux.org}}</ref>
<syntaxhighlight lang="bash">
$ rsync -avAXHS --progress --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found"} / /path/to/backup/folder 
</syntaxhighlight>

Delete all files and directories, within a directory, extremely fast:
<syntaxhighlight lang="bash">
# Make an empty directory somewhere, which is the first path, and the second path is the directory you want to empty.
$ rsync -a --delete /path/to/empty/dir /path/to/dir/to/empty
</syntaxhighlight>

== Connection ==
An rsync process operates by communicating with another rsync process, a sender and a receiver. At startup, an rsync client connects to a peer process. If the transfer is local (that is, between file systems mounted on the same host) the peer can be created with fork, after setting up suitable pipes for the connection. If a remote host is involved, rsync starts a process to handle the connection, typically [[Secure Shell]]. Upon connection, a command is issued to start an rsync process on the remote host, which uses the connection thus established. As an alternative, if the remote host runs an rsync daemon, rsync clients can connect by opening a socket on TCP port 873, possibly using a proxy.<ref>{{Cite web |title=How Rsync Works |url=https://rsync.samba.org/how-rsync-works.html |url-status=live |archive-url=https://web.archive.org/web/20161216173537/http://rsync.samba.org/how-rsync-works.html |archive-date=16 December 2016 |access-date=24 January 2017}}</ref>

Rsync has numerous command line options and configuration files to specify alternative shells, options, commands, possibly with full path, and port numbers.  Besides using remote shells, tunnelling can be used to have remote ports appear as local on the server where an rsync daemon runs. Those possibilities allow adjusting security levels to the state of the art, while a naive rsync daemon can be enough for a local network.

One solution is the <code>[[Dry run (testing)|--dry-run]]</code> option, which allows users to validate their [[command-line argument]]s and to simulate what would happen when copying the data without actually making any changes or transferring any data.

== Algorithm ==
{{more citations needed section|date=March 2015}}

=== Determining which files to send ===
By default, rsync determines which files differ between the sending and receiving systems by checking the modification time and size of each file. If time or size is different between the systems, it transfers the file from the sending to the receiving system. As this only requires reading file directory information, it is quick, but it will miss unusual modifications which change neither.<ref name="man page" />

Rsync performs a slower but comprehensive check if invoked with <code>--checksum</code>. This forces a full checksum comparison on every file present on both systems. Barring rare [[hash collision|checksum collisions]], this avoids the risk of missing changed files at the cost of reading every file present on both systems.

=== Determining which parts of a file have changed ===
The rsync utility uses an [[algorithm]] invented by Australian computer programmer [[Andrew Tridgell]] for efficiently transmitting a structure (such as a file) across a communications link when the receiving computer already has a similar, but not identical, version of the same structure.<ref>{{Cite web |title=RSync – Overview |url=http://tutorials.jenkov.com/rsync/overview.html |url-status=live |archive-url=https://web.archive.org/web/20170410213853/http://tutorials.jenkov.com/rsync/overview.html |archive-date=10 April 2017 |access-date=9 April 2017}}</ref>

The recipient splits its copy of the file into chunks and computes two [[checksum]]s for each chunk: the [[MD5]] [[hash function|hash]], and a weaker but easier to compute '[[Rolling hash|rolling checksum]]'.<ref>{{cite web |url=http://rsync.samba.org/ftp/rsync/src/rsync-3.0.0-NEWS |title=News for rsync 3.0.0 |date=1 March 2008 |archive-url=https://web.archive.org/web/20080320001756/http://rsync.samba.org/ftp/rsync/src/rsync-3.0.0-NEWS |archive-date=20 March 2008 |url-status=dead}}</ref> It sends these checksums to the sender.

The sender computes the checksum for each rolling section in its version of the file having the same size as the chunks used by the recipient's. While the recipient calculates the checksum only for chunks starting at full multiples of the chunk size, the sender calculates the checksum for all sections starting at any address. If any such rolling checksum calculated by the sender matches a checksum calculated by the recipient, then this section is a candidate for not transmitting the content of the section, but only the location in the recipient's file instead. In this case, the sender uses the more computationally expensive MD5 hash to verify that the sender's section and recipient's chunk are equal. Note that the section in the sender may not be at the same start address as the chunk at the recipient. This allows efficient transmission of files which differ by insertions and deletions.<ref>{{cite web |author=Norman Ramsey |url=https://www.cs.tufts.edu/~nr/rsync.html |title=The Rsync Algorithm}}</ref> The sender then sends the recipient those parts of its file that did not match, along with information on where to merge existing blocks into the recipient's version. This makes the copies identical.

The [[rolling hash|rolling checksum]] used in rsync is based on Mark Adler's [[adler-32]] checksum, which is used in [[zlib]], and is itself based on [[Fletcher's checksum]].

If the sender's and recipient's versions of the file have many sections in common, the utility needs to transfer relatively little data to synchronize the files. If typical [[data compression]] algorithms are used, files that are similar when uncompressed may be very different when compressed, and thus the entire file will need to be transferred. Some compression programs, such as [[gzip]], provide a special "rsyncable" mode which allows these files to be efficiently rsynced, by ensuring that local changes in the uncompressed file yield only local changes in the compressed file.

Rsync supports other key features that aid significantly in data transfers or backup. They include compression and decompression of data block by block using [[zstd|Zstandard]], [[LZ4 (compression algorithm)|LZ4]], or [[zlib]], and support for protocols such as [[Secure Shell|ssh]] and [[stunnel]].

== Variations ==
The '''{{visible anchor|rdiff}}''' utility uses the rsync algorithm to generate [[Delta encoding|delta file]]s with the difference from file A to file B (like the utility [[diff]], but in a different delta format). The delta file can then be applied to file A, turning it into file B (similar to the [[patch (Unix)|patch]] utility). rdiff works well with [[binary file]]s.

The '''[[rdiff-backup]]''' script maintains a [[backup]] mirror of a file or directory either locally or remotely over the network on another server. rdiff-backup stores incremental rdiff deltas with the backup, with which it is possible to recreate any backup point.<ref>{{official website
 | 2 = rdiff-backup
 | 1 = rdiff-backup.net/
}}</ref>

The '''librsync''' library used by rdiff is an independent implementation of the rsync algorithm. It does not use the rsync network protocol and does not share any code with the rsync application.<ref name="pool">Pool, Martin; [http://librsync.sourcefrog.net/ "librsync"] {{Webarchive|url=https://web.archive.org/web/20131209003912/http://librsync.sourcefrog.net/ |date=9 December 2013 }}</ref> It is used by [[Dropbox (service)|Dropbox]], rdiff-backup, [[duplicity (software)|duplicity]], and other utilities.<ref name="pool" />

The '''acrosync''' library is an independent, cross-platform implementation of the rsync network protocol.<ref>{{Cite web |last=Chen |first=Gilbert |title=acrosync-library |url=https://github.com/gilbertchen/acrosync-library |url-status=live |archive-url=https://web.archive.org/web/20170210051004/https://github.com/gilbertchen/acrosync-library |archive-date=10 February 2017 |access-date=22 June 2016 |publisher=github.com}}</ref>  Unlike librsync, it is wire-compatible with rsync (protocol version 29 or 30). It is released under the [[Reciprocal Public License]] and used by the commercial rsync software '''Acrosync'''.<ref>{{Cite web |title=acrosync.com |url=https://acrosync.com |url-status=live |archive-url=https://web.archive.org/web/20191220113527/http://acrosync.com/ |archive-date=20 December 2019 |access-date=29 July 2020}}</ref>

The '''[[Duplicity (software)|duplicity]]''' backup software written in '''[[Python (programming_language)|python]]''' allows for incremental backups with simple storage backend services like local file system, [[SSH File Transfer Protocol|sftp]], [[Amazon S3]] and many others. It utilizes librsync to generate delta data against signatures of the previous file versions, encrypting them using [[GNU Privacy Guard|gpg]], and storing them on the backend. For performance reasons a local archive-dir is used to cache backup chain signatures, but can be re-downloaded from the backend if needed.

As of macOS 10.5 and later, there is a special <code>-E</code> or <code>--extended-attributes</code> switch which allows retaining much of the [[HFS Plus|HFS+]] file metadata when syncing between two machines supporting this feature. This is achieved by transmitting the [[Resource Fork]] along with the Data Fork.<ref>{{Cite web |title=Mac Developer Library |url=https://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man1/rsync.1.html |url-status=dead |archive-url=https://web.archive.org/web/20120926232217/http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man1/rsync.1.html |archive-date=26 September 2012 |access-date=18 August 2014 |publisher=Developer.apple.com}}</ref>

'''zsync''' is an rsync-like tool optimized for many downloads per file version. zsync is used by Linux distributions such as [[Ubuntu (operating system)|Ubuntu]]<ref>{{Cite web |title=Zsync Cd Image |url=https://help.ubuntu.com/community/ZsyncCdImage |access-date=6 January 2015 |website=ubuntu.com}}</ref> for distributing fast changing beta [[ISO image]] files. zsync uses the HTTP protocol and .zsync files with pre-calculated rolling hash to minimize server load yet permit diff transfer for network optimization.<ref>[http://zsync.moria.org.uk zsync web site]</ref>

'''[[Rclone]]''' is an open-source tool inspired by rsync that focuses on cloud and other high latency storage. It supports more than 50 different providers and provides an rsync-like interface for cloud storage.<ref>{{Cite web |last=Craig-Wood |first=Nick |title=Overview of cloud storage systems |url=https://rclone.org/overview/ |url-status=live |archive-url=https://web.archive.org/web/20171004030724/https://rclone.org/overview/ |archive-date=4 October 2017 |access-date=10 July 2017 |website=rclone.org}}</ref> However, Rclone does not support rolling checksums for partial file syncing (binary diffs) because cloud storage providers do not usually offer the feature and Rclone avoids storing additional metadata.<ref>{{Cite web |last=Craig-Wood |first=Nick |title=Rclone Frequently Asked Questions |url=https://rclone.org/faq/#why-doesn-t-rclone-support-partial-transfers-binary-diffs-like-rsync |url-status=live |archive-url=https://web.archive.org/web/20220510195418/https://rclone.org/faq/ |archive-date=10 May 2022 |access-date=13 May 2022 |website=rclone.org}}</ref>

== rsync applications ==
{| class="wikitable sortable"
|-
! rowspan="2" | Program !! colspan="3" | Operating system !! rowspan="2" | {{nowrap|[[Free software]]}} !! rowspan="2" | Description
|-
! Linux !! macOS !! Windows 
|-
| [[Back in Time (Linux software)|Back In Time]] || {{Yes}}||{{No}}||{{No}} || {{Yes}} ||
|-
| [[BackupAssist]] || {{No}}|| {{No}}|| {{Yes}} || {{No}} || Direct mirror or with history, VSS.
|-
| [[cwRsync]] || {{No}}|| {{No}}|| {{Yes}} || {{No}} || Based on [[Cygwin]].
|-
| [[Grsync]] || {{Yes}}|| {{Yes}}|| {{Yes}}<ref>{{Cite web |title=Grsync for Windows |url=https://sourceforge.net/projects/grsync-win/ |url-status=live |archive-url=https://web.archive.org/web/20190324193643/https://sourceforge.net/projects/grsync-win/ |archive-date=24 March 2019 |access-date=24 March 2019 |website=SourceForge|date=12 July 2016 }}</ref>|| {{Yes}} || Graphical Interface for rsync.
|-
| [[LuckyBackup]] || {{Yes}}|| {{Yes}}|| {{Yes}} || {{Yes}} ||
|-
| [[rclone]] || {{Yes}}|| {{Yes}}|| {{Yes}}|| {{Yes}}
|Inspired by rsync and supports more than 50 cloud storage providers and other high latency storage services. Does not actually use rsync or support rolling checksums and partial file synchronization.
|-
| [http://dragoman.org/tym tym]|| {{Yes}}|| {{Yes}}|| {{Yes}} || {{Yes}}||Time rsYnc Machine – backup à la [[Time Machine (macOS)|Time Machine]] – [[Bash_(Unix_shell)|Bash]] script
|-
| [[Unison (software)|Unison]]|| {{Yes}}|| {{Yes}}|| {{Yes}} || {{Yes}}||
|}

== See also ==
{{Portal|Free and open-source software}}
*[[casync]]
*[[Remote Differential Compression]]
*[[List of TCP and UDP port numbers]]
*[[Grsync]] – App based on RSync but with graphical user interface
* [[Comparison of file synchronization software]]

== Notes ==
{{notelist}}

== References ==
{{Reflist|30em}}

== External links ==
* {{Official website}}
* [http://rsync.samba.org/tech_report/ Rsync algorithm] – 1998-11-09
* [https://www.samba.org/~tridge/phd_thesis.pdf Doctoral thesis introducing the Rsync algorithm]
* [https://linuxconfig.org/rsync-command-examples/ Rsync examples in Linux (How to use rsync)]

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[[Category:1996 software]]
[[Category:Backup software for Linux]]
[[Category:Data synchronization software]]
[[Category:Free backup software]]
[[Category:Free file transfer software]]
[[Category:Free network-related software]]
[[Category:Free software programmed in C]]
[[Category:Network file transfer protocols]]
[[Category:Unix network-related software]]