rsync

Synchronize file trees across local disks, directories or across a network. (Samba)

SYNTAX

   rsync [OPTION]... SRC [SRC]... [USER@]HOST:DEST

   rsync [OPTION]... [USER@]HOST:SRC DEST

   rsync [OPTION]... SRC [SRC]... DEST

   rsync [OPTION]... [USER@]HOST::SRC [DEST]

   rsync [OPTION]... SRC [SRC]... [USER@]HOST::DEST

   rsync [OPTION]... rsync://[USER@]HOST[:PORT]/SRC [DEST]

DESCRIPTION

rsync is a program that behaves in much the same way that rcp does, but has 
many more options and uses the rsync remote-update protocol to greatly 
speed up file transfers when the destination file already exists.

The rsync remote-update protocol allows rsync to transfer just the 
differences between two sets of files across the network link, using 
an efficient checksum-search algorithm described in the technical report 
that accompanies this package.

Some of the additional features of rsync are:

# 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 rsh or ssh
# does not require root privileges
# pipelining of file transfers to minimize latency costs
# support for anonymous or authenticated rsync servers (ideal for mirroring)

GENERAL

There are six different ways of using rsync. They are:

# for copying local files. This is invoked when neither source nor 
  destination path contains a : separator

# for copying from the local machine to a remote machine using a remote
  shell program as the transport (such as rsh or ssh). 
  This is invoked when the destination path contains a single : separator.

# for copying from a remote machine to the local machine using a remote 
  shell program. This is invoked when the source contains a : separator.

# for copying from a remote rsync server to the local machine.
  This is invoked when the source path contains a :: separator or a rsync:// URL.

# for copying from the local machine to a remote rsync server.
  This is invoked when the destination path contains a :: separator.

# for listing files on a remote machine. This is done the same way as rsync 
  transfers except that you leave off the local destination.

Note that in all cases (other than listing) at least one of the source and 
destination paths must be local.

SETUP

See the file README for installation instructions.

Once installed you can use rsync to any machine that you can use rsh to. 
rsync uses rsh for its communications, unless both the source and destination are local.

You can also specify an alternative to rsh, either by using the -e command line 
option, or by setting the RSYNC_RSH environment variable.

One common substitute is to use ssh, which offers a high degree of security.

Note that rsync must be installed on both the source and destination machines.

USAGE

You use rsync in the same way you use rcp. 
You must specify a source and a destination, one of which may be remote.

Perhaps the best way to explain the syntax is some examples:

   rsync *.c foo:src/

this would transfer all files matching the pattern *.c from the current directory
to the directory src on the machine foo. 
If any of the files already exist on the remote system then the 
rsync remote-update protocol is used to update the file by sending only the differences. 
See the tech report for details.

   rsync -avz foo:src/bar /data/tmp

this would recursively transfer all files from the directory src/bar 
on the machine foo into the /data/tmp/bar directory on the local machine. 
The files are transferred in "archive" mode, which ensures that symbolic links,
devices, attributes, permissions, ownerships etc are preserved in the transfer. 
Additionally, compression will be used to reduce the size of data portions of the transfer.

   rsync -avz foo:src/bar/ /data/tmp

a trailing slash on the source changes this behavior to transfer all files
from the directory src/bar on the machine foo into the /data/tmp/. 
A trailing / on a source name means "copy the contents of this directory". 
Without a trailing slash it means "copy the directory". 
This difference becomes particularly important when using the --delete option.

You can also use rsync in local-only mode, where both the source and destination 
don't have a ':' in the name. 
In this case it behaves like an improved copy command.

  rsync somehost.mydomain.com::

this would list all the anonymous rsync modules available on
the host somehost.mydomain.com. (See the following section for more details.)

CONNECTING TO AN RSYNC SERVER

It is also possible to use rsync without using rsh or ssh as the transport. 
In this case you will connect to a remote rsync server running on TCP port 873.

You may establish the connection via a web proxy by setting the environment variable
 RSYNC_PROXY to a hostname:port pair pointing to your web proxy. 
Note that your web proxy's configuration must allow proxying to port 873.

Using rsync in this way is the same as using it with rsh or ssh except that:

# you use a double colon :: instead of a single colon to separate the hostname 
from the path.

# the remote server may print a message of the day when you connect.

# if you specify no path name on the remote server then the list of accessible 
paths on the server will be shown.

# if you specify no local destination then a listing of the specified files on 
the remote server is provided.

Some paths on the remote server may require authentication. 
If so then you will receive a password prompt when you connect. 
You can avoid the password prompt by setting the environment variable
RSYNC_PASSWORD to the password you want to use or using the --password-file option. 
This may be useful when scripting rsync.

WARNING: On some systems environment variables are visible to all users. 
On those systems using --password-file is recommended.

RUNNING AN RSYNC SERVER

An rsync server is configured using a config file which by default is 
called /etc/rsyncd.conf. Please see the rsyncd.conf(5) man page for more information.

EXAMPLES

Here are some examples of how I use rsync.

To backup my wife's home directory, which consists of large MS Word files and
mail folders, I use a cron job that runs

   rsync -Cavz . arvidsjaur:backup

each night over a PPP link to a duplicate directory on my machine "arvidsjaur".

To synchronize my samba source trees I use the following Makefile targets:

   get:
   rsync -avuzb --exclude '*~' samba:samba/ .

   put:
   rsync -Cavuzb . samba:samba/

   sync: get put

this allows me to sync with a CVS directory at the other end of the link. 
I then do cvs operations on the remote machine, which saves a lot of time 
as the remote cvs protocol isn't very efficient.

I mirror a directory between my "old" and "new" ftp sites with the command

   rsync -az -e ssh --delete ~ftp/pub/samba/ nimbus:"~ftp/pub/tridge/samba"

this is launched from cron every few hours.

OPTIONS SUMMARY

Here is a short summary of the options available in rsync. 
Please refer to the detailed description below for a complete description.

 -v, --verbose               increase verbosity
 -q, --quiet                 decrease verbosity
 -c, --checksum              always checksum
 -a, --archive               archive mode
 -r, --recursive             recurse into directories
 -R, --relative              use relative path names
 -b, --backup                make backups (default ~ suffix)
     --backup-dir            make backups into this directory
     --suffix=SUFFIX         override backup suffix
 -u, --update                update only (don't overwrite newer files)
 -l, --links                 copy symlinks as symlinks
 -L, --copy-links            copy the referent of symlinks
     --copy-unsafe-links     copy links outside the source tree
     --safe-links            ignore links outside the destination tree
 -H, --hard-links            preserve hard links
 -p, --perms                 preserve permissions
 -o, --owner                 preserve owner (root only)
 -g, --group                 preserve group
 -D, --devices               preserve devices (root only)
 -t, --times                 preserve times
 -S, --sparse                handle sparse files efficiently
 -n, --dry-run               show what would have been transferred
 -W, --whole-file            copy whole files, no incremental checks
 -x, --one-file-system       don't cross filesystem boundaries
 -B, --block-size=SIZE       checksum blocking size (default 700)
 -e, --rsh=COMMAND           specify rsh replacement
     --rsync-path=PATH       specify path to rsync on the remote machine
 -C, --cvs-exclude           auto ignore files in the same way CVS does
     --existing              only update files that already exist
     --delete                delete files that don't exist on the sending side
     --delete-excluded       also delete excluded files on the receiving side
     --delete-after          delete after transferring, not before
     --ignore-errors         delete even if there are IO errors
     --max-delete=NUM        don't delete more than NUM files
     --partial               keep partially transferred files
     --force                 force deletion of directories even if not empty
     --numeric-ids           don't map uid/gid values by user/group name
     --timeout=TIME          set IO timeout in seconds
 -I, --ignore-times          don't exclude files that match length and time
     --size-only             only use file size when determining if a file should be transferred
     --modify-window=NUM     Timestamp window (seconds) for file match (default=0)
 -T  --temp-dir=DIR          create temporary files in directory DIR
     --compare-dest=DIR      also compare destination files relative to DIR
 -P                          equivalent to --partial --progress
 -z, --compress              compress file data
     --exclude=PATTERN       exclude files matching PATTERN
     --exclude-from=FILE     exclude patterns listed in FILE
     --include=PATTERN       don't exclude files matching PATTERN
     --include-from=FILE     don't exclude patterns listed in FILE
     --version               print version number
     --daemon                run as a rsync daemon
     --no-detach             do not detach from the parent
     --address=ADDRESS       bind to the specified address
     --config=FILE           specify alternate rsyncd.conf file
     --port=PORT             specify alternate rsyncd port number
     --blocking-io           use blocking IO for the remote shell
     --stats                 give some file transfer stats
     --progress              show progress during transfer
     --log-format=FORMAT     log file transfers using specified format
     --password-file=FILE    get password from FILE
     --bwlimit=KBPS          limit I/O bandwidth, KBytes per second
 -f, --read-batch=FILE       read batch file
 -F, --write-batch           write batch file
 -h, --help                  show this help screen

OPTIONS

rsync uses the GNU long options package. 
Many of the command line options have two variants, one short and one long. 
These are shown below, separated by commas. 
Some options only have a long variant. 
The '=' for options that take a parameter is optional; whitespace can be used instead.

-h, --help
    Print a short help page describing the options available in rsync

--version
    print the rsync version number and exit

-v, --verbose
    This option increases the amount of information you are given during the transfer. 
    By default, rsync works silently. 
    A single -v will give you information about what files are being transferred 
    and a brief summary at the end. 
    Two -v flags will give you information on what files are being skipped and
    slightly more information at the end.
    More than two -v flags should only be used if you are debugging rsync.

-q, --quiet
    This option decreases the amount of information you are given during the transfer,
    notably suppressing information messages from the remote server.
    This flag is useful when invoking rsync from cron.

-I, --ignore-times
    Normally rsync will skip any files that are already the same length and 
    have the same time-stamp. This option turns off this behavior.

--size-only
    Normally rsync will skip any files that are already the same length and 
    have the same time-stamp.
    With the --size-only option files will be skipped if they have the same size,
    regardless of timestamp. This is useful when starting to use rsync after
    using another mirroring system which may not preserve timestamps exactly.

--modify-window
    When comparing two timestamps rsync treats the timestamps as being equal if
    they are within the value of modify_window. 
    This is normally zero, but you may find it useful to set this to a larger value
    in some situations. In particular, when transferring to/from FAT filesystems
    which cannot represent times with a 1 second resolution this option is useful.

-c, --checksum
    This forces the sender to checksum all files using a 128-bit MD4 checksum
    before transfer. The checksum is then explicitly checked on the receiver and
    any files of the same name which already exist and have the same checksum and 
    size on the receiver are skipped. This option can be quite slow.

-a, --archive
    This is equivalent to -rlptgoD. It is a quick way of saying you want recursion and
    want to preserve almost everything.

    Note however that -a does not preserve hardlinks, because finding multiply-linked
    files is expensive. You must separately specify -H.

-r, --recursive
    This tells rsync to copy directories recursively. 
    If you don't specify this then rsync won't copy directories at all.

-R, --relative
    Use relative paths. This means that the full path names specified on the
    command line are sent to the server rather than just the last parts of the
    filenames. This is particularly useful when you want to send several different
    directories at the same time.
    For example, if you used the command

rsync foo/bar/foo.c remote:/tmp/

    then this would create a file called foo.c in /tmp/ on the remote machine. 
    If instead you used

rsync -R foo/bar/foo.c remote:/tmp/

    then a file called /tmp/foo/bar/foo.c would be created on the remote machine.
    The full path name is preserved.

-b, --backup
    With this option preexisting destination files are renamed with a ~ extension as
    each file is transferred.
    You can control the backup suffix using the --suffix option.

--backup-dir=DIR
    In combination with the --backup option, this tells rsync to store all
    backups in the specified directory. This is very useful for incremental backups.

--suffix=SUFFIX
    This option allows you to override the default backup suffix
    used with the -b option. The default is a ~.

-u, --update
    This forces rsync to skip any files for which the destination file already
    exists and has a date later than the source file.

-l, --links
    When symlinks are encountered, recreate the symlink on the destination.

-L, --copy-links
    When symlinks are encountered, the file that they point to is copied,
    rather than the symlink.

--copy-unsafe-links
    This tells rsync to copy the referent of symbolic links that point outside
    the source tree. Absolute symlinks are also treated like ordinary files,
    and so are any symlinks in the source path itself when --relative is used.

--safe-links
    This tells rsync to ignore any symbolic links which point outside the
    destination tree. All absolute symlinks are also ignored.
    Using this option in conjunction with --relative may give unexpected results.

-H, --hard-links
    This tells rsync to recreate hard links on the remote system to be the same
    as the local system. Without this option hard links are treated like regular files.

    Note that rsync can only detect hard links if both parts of the link are
    in the list of files being sent.

    This option can be quite slow, so only use it if you need it.

-W, --whole-file
    With this option the incremental rsync algorithm is not used and the whole
    file is sent as-is instead. The transfer may be faster if this option is
    used when the bandwidth between the source and target machines is higher
    than the bandwidth to disk (especially when the "disk" is actually a networked file system).
    This is the default when both the source and target are on the local machine.

-p, --perms
    This option causes rsync to update the remote permissions to be the same as
    the local permissions.

-o, --owner
    This option causes rsync to set the owner of the destination file to be the
    same as the source file. On most systems, only the super-user can set file ownership.

-g, --group
    This option causes rsync to set the group of the destination file to be the
    same as the source file. If the receiving program is not running as the super-user,
    only groups that the receiver is a member of will be preserved
    (by group name, not group id number).

-D, --devices
    This option causes rsync to transfer character and block device information to
    the remote system to recreate these devices.
    This option is only available to the super-user.

-t, --times
    This tells rsync to transfer modification times along with the files and update
    them on the remote system. Note that if this option is not used,
    the optimization that excludes files that have not been modified cannot be effective;
    in other words, a missing -t or -a will cause the next transfer to behave as if
    it used -I, and all files will have their checksums compared and show up in log
    messages even if they haven't changed.

-n, --dry-run
    This tells rsync to not do any file transfers, instead it will just report the
    actions it would have taken.

-S, --sparse
    Try to handle sparse files efficiently so they take up less space on the
    destination.

    NOTE: Don't use this option when the destination is a Solaris "tmpfs" filesystem.
    It doesn't seem to handle seeks over null regions correctly and ends up corrupting
    the files.

-x, --one-file-system
    This tells rsync not to cross filesystem boundaries when recursing.
    This is useful for transferring the contents of only one filesystem.

--existing
    This tells rsync not to create any new files - only update files that already
    exist on the destination.

--max-delete=NUM
    This tells rsync not to delete more than NUM files or directories.
    This is useful when mirroring very large trees to prevent disasters.

--delete
    This tells rsync to delete any files on the receiving side that aren't on
    the sending side. Files that are excluded from transfer are excluded from
    being deleted unless you use --delete-excluded.

    This option has no effect if directory recursion is not selected.

    This option can be dangerous if used incorrectly! It is a very good idea to
    run first using the dry run option (-n) to see what files would be deleted
    to make sure important files aren't listed.

    If the sending side detects any IO errors then the deletion of any files at
    the destination will be automatically disabled.
    This is to prevent temporary filesystem failures (such as NFS errors) on the
    sending side causing a massive deletion of files on the destination.
    You can override this with the --ignore-errors option.

--delete-excluded
    In addition to deleting the files on the receiving side that are not on
    the sending side, this tells rsync to also delete any files on the receiving side
    that are excluded (see --exclude).

--delete-after
    By default rsync does file deletions before transferring files to try to
    ensure that there is sufficient space on the receiving filesystem.
    If you want to delete after transferring then use the --delete-after switch.

--ignore-errors
    Tells --delete to go ahead and delete files even when there are IO errors.

--force
    This options tells rsync to delete directories even if they are not empty.
    This applies to both the --delete option and to cases where rsync tries to
    copy a normal file but the destination contains a directory of the same name.

    Since this option was added, deletions were reordered to be done depth-first
    so it is hardly ever needed anymore except in very obscure cases.

-B , --block-size=BLOCKSIZE
    This controls the block size used in the rsync algorithm.
    See the technical report for details.

-e, --rsh=COMMAND
    This option allows you to choose an alternative remote shell program to
    use for communication between the local and remote copies of rsync.
    By default, rsync will use rsh, but you may like to instead use ssh because
    of its high security.

    You can also choose the remote shell program using the RSYNC_RSH
    environment variable.

    See also the --blocking-io option which is affected by this option.

--rsync-path=PATH
    Use this to specify the path to the copy of rsync on the remote machine.
    Useful when it's not in your path. Note that this is the full path to the binary,
    not just the directory that the binary is in.

--exclude=PATTERN
    This option allows you to selectively exclude certain files from the list of
    files to be transferred.
    This is most useful in combination with a recursive transfer.

    You may use as many --exclude options on the command line as you like to
    build up the list of files to exclude.

    See the section on exclude patterns for information on the syntax of this option.

--exclude-from=FILE
    This option is similar to the --exclude option, but instead it adds all exclude
    patterns listed in the file FILE to the exclude list.
    Blank lines in FILE and lines starting with ';' or '#' are ignored.

--include=PATTERN
    This option tells rsync to not exclude the specified pattern of filenames.
    This is useful as it allows you to build up quite complex exclude/include rules.

    See the section of exclude patterns for information on the syntax of this option.

--include-from=FILE
    This specifies a list of include patterns from a file.

-C, --cvs-exclude
    This is a useful shorthand for excluding a broad range of files that you often
    don't want to transfer between systems.
    It uses the same algorithm that CVS uses to determine if a file should be ignored.

    The exclude list is initialized to:

    RCS SCCS CVS CVS.adm RCSLOG cvslog.* tags TAGS .make.state .nse_depinfo *~ #* .#* ,* *.old *.bak *.BAK *.orig *.rej .del-* *.a *.o *.obj *.so *.Z *.elc *.ln core

    then files listed in a $HOME/.cvsignore are added to the list and any files
    listed in the CVSIGNORE environment variable (space delimited).

    Finally, any file is ignored if it is in the same directory as a .cvsignore file
    and matches one of the patterns listed therein.
    See the cvs(1) manual for more information.

--csum-length=LENGTH
    By default the primary checksum used in rsync is a very strong 16 byte MD4 checksum.
    In most cases you will find that a truncated version of this checksum is quite
    efficient, and this will decrease the size of the checksum data sent over the link,
    making things faster.

    You can choose the number of bytes in the truncated checksum
    using the --csum-length option. Any value less than or equal to 16 is valid.

    Note that if you use this option then you run the risk of ending up with an
    incorrect target file. The risk with a value of 16 is microscopic and can be
    safely ignored (the universe will probably end before it fails)
    but with smaller values the risk is higher.

    Current versions of rsync actually use an adaptive algorithm for the checksum
    length by default, using a 16 byte file checksum to determine if a 2nd pass is
    required with a longer block checksum.
    Only use this option if you have read the source code and know what you are doing.

-T, --temp-dir=DIR
    This option instructs rsync to use DIR as a scratch directory when creating
    temporary copies of the files transferred on the receiving side.
    The default behavior is to create the temporary files in the receiving directory.

--compare-dest=DIR
    This option instructs rsync to use DIR on the destination machine as an
    additional directory to compare destination files against when doing transfers.
    This is useful for doing transfers to a new destination while leaving existing
    files intact, and then doing a flash-cutover when all files have been successfully
    transferred (for example by moving directories around and removing the old
    directory, although this requires also doing the transfer with -I to avoid
    skipping files that haven't changed).
    This option increases the usefulness of --partial because partially transferred
    files will remain in the new temporary destination until they have a chance to be
    completed. If DIR is a relative path, it is relative to the destination directory.

-z, --compress
    With this option, rsync compresses any data from the files that it sends to the
    destination machine. This option is useful on slow links. The compression method
    used is the same method that gzip uses.

    Note this this option typically achieves better compression ratios that can be
    achieved by using a compressing remote shell, or a compressing transport,
    as it takes advantage of the implicit information sent for matching data blocks.

--numeric-ids
    With this option rsync will transfer numeric group and user ids rather than
    using user and group names and mapping them at both ends.

    By default rsync will use the user name and group name to determine what
    ownership to give files. The special uid 0 and the special group 0 are never
    mapped via user/group names even if the --numeric-ids option is not specified.

    If the source system is a daemon using chroot, or if a user or group name
    does not exist on the destination system, then the numeric id from the
    source system is used instead.

--timeout=TIMEOUT
    This option allows you to set a maximum IO timeout in seconds.
    If no data is transferred for the specified time then rsync will exit.
    The default is 0, which means no timeout.

--daemon
    This tells rsync that it is to run as a daemon.
    The daemon may be accessed using the host::module or rsync://host/module/ syntax.

    If standard input is a socket then rsync will assume that it is being
    run via inetd, otherwise it will detach from the current terminal and 
    become a background daemon. The daemon will read the config file (/etc/rsyncd.conf)
    on each connect made by a client and respond to requests accordingly.
     See the rsyncd.conf(5) man page for more details.

--no-detach
    When running as a daemon, this option instructs rsync to not detach itself and
    become a background process.
    This option is required when running as a service on Cygwin, and may also be useful
    when rsync is supervised by a program such as daemontools or AIX's System Resource
    Controller. --no-detach is also recommended when rsync is run under a debugger.
    This option has no effect if rsync is run from inetd or sshd.

--address
    By default rsync will bind to the wildcard address when run as a daemon with
    the --daemon option or when connecting to a rsync server.
    The --address option allows you to specify a specific IP address (or hostname) to
    bind to. This makes virtual hosting possible in conjunction with the --config option.

--config=FILE
    This specifies an alternate config file than the default /etc/rsyncd.conf.
    This is only relevant when --daemon is specified.

--port=PORT
    This specifies an alternate TCP port number to use rather than the default port 873.

--blocking-io
    This tells rsync to use blocking IO when launching a remote shell transport.
    If -e or --rsh are not specified or are set to the default "rsh",
    this defaults to blocking IO, otherwise it defaults to non-blocking IO.
    You may find the --blocking-io option is needed for some remote shells that can't
    handle non-blocking IO. Ssh prefers blocking IO.

--log-format=FORMAT
    This allows you to specify exactly what the rsync client logs to stdout on
    a per-file basis. The log format is specified using the same format conventions
    as the log format option in rsyncd.conf.

--stats
    This tells rsync to print a verbose set of statistics on the file transfer,
    allowing you to tell how effective the rsync algorithm is for your data.

--partial
    By default, rsync will delete any partially transferred file if the transfer
    is interrupted. In some circumstances it is more desirable to keep partially
    transferred files. Using the --partial option tells rsync to keep the partial
    file which should make a subsequent transfer of the rest of the file much faster.

--progress
    This option tells rsync to print information showing the progress of the transfer.
    This gives a bored user something to watch.

    This option is normally combined with -v. Using this option without the -v option
    will produce weird results on your display.

-P
    The -P option is equivalent to --partial --progress.
    I found myself typing that combination quite often so I created an option to make
    it easier.

--password-file
    This option allows you to provide a password in a file for accessing a
    remote rsync server. Note that this option is only useful when accessing a
    rsync server using the built in transport, not when using a remote shell as
    the transport. The file must not be world readable.
    It should contain just the password as a single line.

--bwlimit=KBPS
    This option allows you to specify a maximum transfer rate in kilobytes per second.
    This option is most effective when using rsync with large files
    (several megabytes and up). Due to the nature of rsync transfers,
    blocks of data are sent, then if rsync determines the transfer was too fast,
    it will wait before sending the next data block.
    The result is an average transfer rate equalling the specified limit.
    A value of zero specifies no limit.

--read-batch
    Apply a previously generated change batch.

--write-batch
    Generate a set of files that can be transferred as a batch update.

EXCLUDE PATTERNS

The exclude and include patterns specified to rsync allow for flexible selection of
which files to transfer and which files to skip.

rsync builds an ordered list of include/exclude options as specified on the 
command line. When a filename is encountered, rsync checks the name against each
 exclude/include pattern in turn. The first matching pattern is acted on. 
If it is an exclude pattern, then that file is skipped. 
If it is an include pattern then that filename is not skipped. 
If no matching include/exclude pattern is found then the filename is not skipped.

Note that when used with -r (which is implied by -a), every subcomponent of
every path is visited from top down, so include/exclude patterns get applied 
recursively to each subcomponent.

Note also that the --include and --exclude options take one pattern each.
To add multiple patterns use the --include-from and --exclude-from options
 or multiple --include and --exclude options.

The patterns can take several forms. The rules are:

# if the pattern starts with a / then it is matched against the start of the filename,
  otherwise it is matched against the end of the filename. 
  Thus "/foo" would match a file called "foo" at the base of the tree.
  On the other hand, "foo" would match any file called "foo" anywhere in the tree
  because the algorithm is applied recursively from top down; it behaves as if each
  path component gets a turn at being the end of the file name.

# if the pattern ends with a / then it will only match a directory, not a file,
  link or device.

# if the pattern contains a wildcard character from the set *?[ then expression
  matching is applied using the shell filename matching rules.
  Otherwise a simple string match is used.

# if the pattern includes a double asterisk "**" then all wildcards in the pattern
  will match slashes, otherwise they will stop at slashes.

# if the pattern contains a / (not counting a trailing /) then it is matched
  against the full filename, including any leading directory.
  If the pattern doesn't contain a / then it is matched only against the final
  component of the filename. Again, remember that the algorithm is applied recursively
  so "full filename" can actually be any portion of a path.

# if the pattern starts with "+ " (a plus followed by a space) then it is always
  considered an include pattern, even if specified as part of an exclude option.
  The "+ " part is discarded before matching.

# if the pattern starts with "- " (a minus followed by a space) then it is always
  considered an exclude pattern, even if specified as part of an include option.
  The "- " part is discarded before matching.

# if the pattern is a single exclamation mark ! then the current include/exclude list
  is reset, removing all previously defined patterns.

The +/- rules are most useful in exclude lists, allowing you to have a single
  exclude list that contains both include and exclude options.

If you end an exclude list with --exclude '*', note that since the algorithm is applied recursively that unless you explicitly include parent directories of files you want to include then the algorithm will stop at the parent directories and never see the files below them. To include all directories, use --include '*/' before the --exclude '*'.

Here are some exclude/include examples:

# --exclude "*.o"   would exclude all filenames matching *.o
# --exclude "/foo"  would exclude a file in the base directory called foo
# --exclude "foo/"  would exclude any directory called foo.
# --exclude "/foo/*/bar"  would exclude any file called bar two levels below a
                          base directory called foo.
# --exclude "/foo/**/bar" would exclude any file called bar two or more levels below
                          a base directory called foo.
# --include "*/" --include "*.c" --exclude "*"
                          would include all directories
                          and C source files
# --include "foo/" --include "foo/bar.c" --exclude "*"
                    would include only foo/bar.c (the foo/ directory must be
                    explicitly included or it would be excluded by the "*")

BATCH MODE

The following call generates 4 files that encapsulate the information for
synchronizing the contents of target_dir with the updates found in src_dir

$ rsync -F [other rsync options here] \
/somewhere/src_dir /somewhere/target_dir

The generated files are labeled with a common timestamp:

# rsync_argvs. command-line arguments
# rsync_flist. rsync internal file metadata
# rsync_csums. rsync checksums
# rsync_delta. data blocks for file update & change

See http://www.ils.unc.edu/i2dsi/unc_rsync+.html for papers and technical reports.

SYMBOLIC LINKS

Three basic behaviours are possible when rsync encounters a symbolic link in
the source directory.

By default, symbolic links are not transferred at all.
A message "skipping non-regular" file is emitted for any symlinks that exist.

If --links is specified, then symlinks are recreated with the same target
on the destination. Note that --archive implies --links.

If --copy-links is specified, then symlinks are "collapsed" by copying their referent,
rather than the symlink.

rsync also distinguishes "safe" and "unsafe" symbolic links.
An example where this might be used is a web site mirror that wishes ensure the 
rsync module they copy does not include symbolic links to /etc/passwd in the public
section of the site. Using --copy-unsafe-links will cause any links to be copied
as the file they point to on the destination.
Using --safe-links will cause unsafe links to be ommitted altogether.

DIAGNOSTICS

rsync occasionally produces error messages that may seem a little cryptic. 
The one that seems to cause the most confusion is 
"protocol version mismatch - is your shell clean?".

This message is usually caused by your startup scripts or remote shell facility
producing unwanted garbage on the stream that rsync is using for its transport. 
The way to diagnose this problem is to run your remote shell like this:

   rsh remotehost /bin/true > out.dat


then look at out.dat. If everything is working correctly then out.dat should be
a zero length file. If you are getting the above error from rsync then you will
probably find that out.dat contains some text or data. 
Look at the contents and try to work out what is producing it. 
The most common cause is incorrectly configured shell startup scripts
 (such as .cshrc or .profile) that contain output statements for non-interactive logins.

If you are having trouble debugging include and exclude patterns,
then try specifying the -vv option.
At this level of verbosity rsync will show why each individual file is included or
excluded.

EXIT VALUES

RERR_SYNTAX 1
    Syntax or usage error

RERR_PROTOCOL 2
    Protocol incompatibility

RERR_FILESELECT 3
    Errors selecting input/output files, dirs

RERR_UNSUPPORTED 4
    Requested action not supported: an attempt was made to manipulate 
    64-bit files on a platform that cannot support them; or an option was
    speciifed that is supported by the client and not by the server.

RERR_SOCKETIO 10
    Error in socket IO

RERR_FILEIO 11
    Error in file IO

RERR_STREAMIO 12
    Error in rsync protocol data stream

RERR_MESSAGEIO 13
    Errors with program diagnostics

RERR_IPC 14
    Error in IPC code

RERR_SIGNAL 20
    Received SIGUSR1 or SIGINT

RERR_WAITCHILD 21
    Some error returned by waitpid()

RERR_MALLOC 22
    Error allocating core memory buffers

RERR_TIMEOUT 30
Timeout in data send/receive

ENVIRONMENT VARIABLES

CVSIGNORE
    The CVSIGNORE environment variable supplements any ignore patterns in .cvsignore files.
    See the --cvs-exclude option for more details.

RSYNC_RSH
    The RSYNC_RSH environment variable allows you to override the default shell used as
    the transport for rsync. This can be used instead of the -e option.

RSYNC_PROXY
    The RSYNC_PROXY environment variable allows you to redirect your rsync client to
    use a web proxy when connecting to a rsync daemon.
    You should set RSYNC_PROXY to a hostname:port pair.

RSYNC_PASSWORD
    Setting RSYNC_PASSWORD to the required password allows you to run authenticated
    rsync connections to a rsync daemon without user intervention.
    Note that this does not supply a password to a shell transport such as ssh.

USER or LOGNAME
    The USER or LOGNAME environment variables are used to determine the default
    username sent to a rsync server.

HOME
    The HOME environment variable is used to find the user's default .cvsignore file.

FILES

/etc/rsyncd.conf

Download latest version (plus docs)
rsync.samba.org

Related commands:

rsyncd.conf(5)
cp - Copy one or more files to another location
install - Copy files and set attributes
dd - Data Dump - convert and copy a file (use for RAW storage)
remsync - Synchronize remote files via email

Equivalent Windows NT commands:

ROBOCOPY - Robust File and Folder Copy