http://rsync.samba.org/
用的是rsync-3.0.6-12.el6.x86_64
Rsync version 3.1.1 released
June 22nd, 2014
Rsync version 3.1.1 has been released. This is a bug-fix release.
rsync is an open source utility that provides fast incremental file transfer. rsync is freely available under the GNU General Public License and is currently being maintained by Wayne Davison.
rsync是一个提供快速增量文件传输的开源工具。它在GNU gpl下自由可得，当前由Wayne Davison维护。
rsync features
rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand.
rsync是unix下的一个文件传输程序。它使用rsync 算法，这个算法提供一个非常快速的方法将远程文件带进sync。通过链路只发送有差异的文件，不用事先查询两组文件都存在于链路的其中一端
Some features of rsync include
- can update whole directory trees and filesystems
- optionally preserves symbolic links, hard links, file ownership, permissions, devices and times
- requires no special privileges to install
- internal pipelining reduces latency for multiple files
- can use rsh, ssh or direct sockets as the transport
- supports anonymous rsync which is ideal for mirroring
不需要什么特殊的权限来安装
内部的流水线为多个文件减少了延迟
能使用rsh,ssh,或直接sockets作为运输工具。
man rsync
Rsync is a fast and extraordinarily versatile file copying tool. It can copy locally, to/from another host over any remote shell, or to/from a remote rsync daemon.
rsync是一个快速的，非常全面的文件拷贝工具。它能本地拷贝，通过任意远程shell远程拷贝，或
It offers a large number of options that control every aspect of its behavior and permit very flexible specification of the set of files to be copied.
它提供大量的选项来控制行为的每一方面并且允许很灵活地指定要拷贝的组文件。
It is famous for its delta-transfer algorithm, which reduces the amount of data sent over the network by sending only the differences between the source files and the existing files in the destination.
rsync因delta-transfer算法而闻名，这个算法减少了通过网络发送的数据量，在源文件与目的地中已存在的文件之间只发送差异
Rsync is widely used for backups and mirroring and as an improved copy command for everyday use.
rsync广泛用于备份与镜像，和作为一个每天使用的copy命令的改进。
Rsync finds files that need to be transferred using a "quick check" algorithm (by default) that looks for files that have changed in size or in last-modified time.
rsync查找需要被传送的文件，使用一个快速检查算法，这个算法按大小或最近修改时间来寻找已经更改的文件。
Any changes in the other preserved attributes (as requested by options) are made on the destination file directly when the quick check indicates that the file's data does not need to be updated.
保留属性的任何更改，当快速检查指示文件的数据不需要被更新时直接生成目的文件
Some of the additional features of rsync are:
rsync的一些额外特性是：
support for copying links, devices, owners, groups, and permissions
exclude and exclude-from options similar to GNU tar
a CVS exclude mode for ignoring the same files that CVS would ignore
can use any transparent remote shell, including ssh or rsh
does not require super-user privileges
pipelining of file transfers to minimize latency costs
support for anonymous or authenticated rsync daemons (ideal for mirroring)