Editing Rsync (section)

{{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).