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.

       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.  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 is widely used for backups and mirroring and as an improved copy command for everyday use.

rsync syntax

      Local:  rsync [OPTION...] SRC... [DEST]

Access via remote shell:

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

Access via rsync daemon:

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

   Usages with just one SRC arg and no DEST arg will list the source files instead of copying.

Mostly used options:  rsync -auvx SRC DEST

The four options -a,-u,-v,-x provide identical copy between SRC and DEST.

Copying a directory from remote server to local

# rsync -auvx test::backup/sbin .
receiving incremental file list
...
sbin/delete_fc_luns
sbin/fincore
sbin/lip_fc_hosts
...
sbin/_Inline/lib/auto/fincore_4f4e/fincore_4f4e.so

sent 527 bytes  received 188353 bytes  377760.00 bytes/sec
total size is 186500  speedup is 0.99

Details for options -a,-u,-v,-x

        -a, --archive               archive mode; equals -rlptgoD (no -H,-A,-X)
            --no-OPTION             turn off an implied OPTION (e.g. --no-D)
        -u, --update                skip files that are newer on the receiver
            --inplace               update destination files in-place
            --append                append data onto shorter files
            --append-verify         --append w/old data in file checksum
        -v, --verbose               increase verbosity
        -x, --one-file-system       don't cross filesystem boundaries

A little bit more about archive option, particularly useful if you use rsync for backup purpose.

       -a, --archive
           This  is equivalent to -rlptgoD. It is a quick way of saying you want recursion
and want to preserve almost everything (with -H being a notable omission). 
The only exception to the above equivalence is when --files-from is specified,
in which case -r is not implied.

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

Compress during transfer

with -z option, compress option is enabled during transfer

Show transfer progress during transfer

with --progress, you can see transfer progress during transfer

Example for compress and progress transfer

# rsync -auvxz --progress test::backup/sbin .
receiving incremental file list
sbin/
...
sbin/delete_fc_luns
         461 100%  450.20kB/s    0:00:00 (xfer#4, to-check=26/31)
sbin/fincore
        9864 100%  234.95kB/s    0:00:00 (xfer#5, to-check=25/31)
...

Exclude option

with --exclude, --include option, you can exclude/exclude some files when transfer.

You can also use --max-size option to exclude large files in similar way

rsync -auvxz --progress --exclude 'xfs*' remotehost::backup/sbin .

Interesting option, output a change summary for all updates

-i, --itemize-changes       output a change-summary for all updates

# rsync -avi test::backup/sbin .
receiving incremental file list
.d..t...... sbin/
>f.st...... sbin/ls.out
>f+++++++++ sbin/xfs_irecover
>f+++++++++ sbin/xfs_irecover.c
>f+++++++++ sbin/xfs_irecover_sl5
Here is description for above result
> specifies that a file is being transferred to the local host.
f represents that it is a file.
s represents size changes are there.
t represents timestamp changes are there.
o owner changed
g group changed.

Deletion option

--delete option, interesting, ha?
            --delete                delete extraneous files from dest dirs
            --delete-before         receiver deletes before transfer (default)
            --delete-during         receiver deletes during xfer, not before
            --delete-delay          find deletions during, delete after
            --delete-after          receiver deletes after transfer, not before
            --delete-excluded       also delete excluded files from dest dirs

Example below is to do regular rsync, but exclude files end with "*lun",
in addition to that, it deletes excluded files from DEST.:

# rsync -auvxz --progress --exclude '*luns' --delete-excluded test::backup/sbin .
receiving incremental file list
deleting sbin/scan_fc_luns
deleting sbin/ls_fc_luns
deleting sbin/delete_fc_luns

sent 45 bytes  received 698 bytes  1486.00 bytes/sec
total size is 181556  speedup is 244.36

Advanced usage

We already tried remote server daemon since begining, see how to setup rsync server

Multiple files copy

The syntax for requesting multiple files from a remote host is done by specifying additional remote-host args in the same style as the first, or with the hostname omitted. 

For instance, all these work:

              rsync -av host:file1 :file2 host:file{3,4} /dest/
              rsync -av host::modname/file{1,2} host::modname/file3 /dest/
              rsync -av host::modname/file1 ::modname/file{3,4}

 Older versions of rsync required using quoted spaces in the SRC, like these examples:

              rsync -av host:'dir1/file1 dir2/file2' /dest
              rsync host::'modname/dir1/file1 modname/dir2/file2' /dest

Remote shell

-e option, rsync allows you to specify the remote shell which you want to use.

You can use rsync ssh to enable the secured remote connection

       -e, --rsh=COMMAND           specify the remote shell to use

More options to play with

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                 suppress non-error messages
            --no-motd               suppress daemon-mode MOTD (see caveat)
        -c, --checksum              skip based on checksum, not mod-time & size
        -a, --archive               archive mode; equals -rlptgoD (no -H,-A,-X)
            --no-OPTION             turn off an implied OPTION (e.g. --no-D)
        -r, --recursive             recurse into directories
        -R, --relative              use relative path names
            --no-implied-dirs       don't send implied dirs with --relative
        -b, --backup                make backups (see --suffix & --backup-dir)
            --backup-dir=DIR        make backups into hierarchy based in DIR
            --suffix=SUFFIX         backup suffix (default ~ w/o --backup-dir)
        -u, --update                skip files that are newer on the receiver
            --inplace               update destination files in-place
            --append                append data onto shorter files
            --append-verify         --append w/old data in file checksum
        -d, --dirs                  transfer directories without recursing using
                                    "-r --exclude='/*/*'" (rsync 2.6.x compatible)
            --new-dirs              transfer directories without recursing
                                    (rsync 3.0.x compatible)
        -l, --links                 copy symlinks as symlinks
        -L, --copy-links            transform symlink into referent file/dir
            --copy-unsafe-links     only "unsafe" symlinks are transformed
            --safe-links            ignore symlinks that point outside the tree
        -k, --copy-dirlinks         transform symlink to dir into referent dir
        -K, --keep-dirlinks         treat symlinked dir on receiver as dir
        -H, --hard-links            preserve hard links
        -p, --perms                 preserve permissions
        -E, --executability         preserve executability
            --chmod=CHMOD           affect file and/or directory permissions
        -A, --acls                  preserve ACLs (implies -p)
        -X, --xattrs                preserve extended attributes
        -o, --owner                 preserve owner (super-user only)
        -g, --group                 preserve group
            --devices               preserve device files (super-user only)
            --specials              preserve special files
        -D                          same as --devices --specials
        -t, --times                 preserve modification times
        -O, --omit-dir-times        omit directories from --times
            --super                 receiver attempts super-user activities
            --fake-super            store/recover privileged attrs using xattrs
        -S, --sparse                handle sparse files efficiently
        -n, --dry-run               perform a trial run with no changes made
        -W, --whole-file            copy files whole (w/o delta-xfer algorithm)
        -x, --one-file-system       don't cross filesystem boundaries
        -B, --block-size=SIZE       force a fixed checksum block-size
        -e, --rsh=COMMAND           specify the remote shell to use
            --rsync-path=PROGRAM    specify the rsync to run on remote machine
            --existing              skip creating new files on receiver
            --ignore-existing       skip updating files that exist on receiver
            --remove-source-files   sender removes synchronized files (non-dir)
            --del                   an alias for --delete-during
            --delete                delete extraneous files from dest dirs
            --delete-before         receiver deletes before transfer (default)
            --delete-during         receiver deletes during xfer, not before
            --delete-delay          find deletions during, delete after
            --delete-after          receiver deletes after transfer, not before
            --delete-excluded       also delete excluded files from dest dirs
            --ignore-errors         delete even if there are I/O errors
            --force                 force deletion of dirs even if not empty
            --max-delete=NUM        don't delete more than NUM files
            --max-size=SIZE         don't transfer any file larger than SIZE
            --min-size=SIZE         don't transfer any file smaller than SIZE
            --partial               keep partially transferred files
            --partial-dir=DIR       put a partially transferred file into DIR
            --delay-updates         put all updated files into place at end
        -m, --prune-empty-dirs      prune empty directory chains from file-list
            --numeric-ids           don't map uid/gid values by user/group name
            --timeout=SECONDS       set I/O timeout in seconds
            --contimeout=SECONDS    set daemon connection timeout in seconds
        -I, --ignore-times          don't skip files that match size and time
            --size-only             skip files that match in size
            --modify-window=NUM     compare mod-times with reduced accuracy
        -T, --temp-dir=DIR          create temporary files in directory DIR
        -y, --fuzzy                 find similar file for basis if no dest file
            --compare-dest=DIR      also compare received files relative to DIR
            --copy-dest=DIR         ... and include copies of unchanged files
            --link-dest=DIR         hardlink to files in DIR when unchanged
        -z, --compress              compress file data during the transfer
            --compress-level=NUM    explicitly set compression level
            --skip-compress=LIST    skip compressing files with suffix in LIST
        -C, --cvs-exclude           auto-ignore files in the same way CVS does
        -f, --filter=RULE           add a file-filtering RULE
        -F                          same as --filter='dir-merge /.rsync-filter'
                                    repeated: --filter='- .rsync-filter'
            --exclude=PATTERN       exclude files matching PATTERN
            --exclude-from=FILE     read exclude patterns from FILE
            --include=PATTERN       don't exclude files matching PATTERN
            --include-from=FILE     read include patterns from FILE
            --files-from=FILE       read list of source-file names from FILE
        -0, --from0                 all *from/filter files are delimited by 0s
        -s, --protect-args          no space-splitting; wildcard chars only
            --address=ADDRESS       bind address for outgoing socket to daemon
            --port=PORT             specify double-colon alternate port number
            --sockopts=OPTIONS      specify custom TCP options
            --blocking-io           use blocking I/O for the remote shell
            --stats                 give some file-transfer stats
        -8, --8-bit-output          leave high-bit chars unescaped in output
        -h, --human-readable        output numbers in a human-readable format
            --progress              show progress during transfer
        -P                          same as --partial --progress
        -i, --itemize-changes       output a change-summary for all updates
            --out-format=FORMAT     output updates using the specified FORMAT
            --log-file=FILE         log what we're doing to the specified FILE
            --log-file-format=FMT   log updates using the specified FMT
            --password-file=FILE    read daemon-access password from FILE
            --list-only             list the files instead of copying them
            --bwlimit=KBPS          limit I/O bandwidth; KBytes per second
            --write-batch=FILE      write a batched update to FILE
            --only-write-batch=FILE like --write-batch but w/o updating dest
            --read-batch=FILE       read a batched update from FILE
           --protocol=NUM          force an older protocol version to be used
            --iconv=CONVERT_SPEC    request charset conversion of filenames
            --checksum-seed=NUM     set block/file checksum seed (advanced)
        -4, --ipv4                  prefer IPv4
        -6, --ipv6                  prefer IPv6
            --version               print version number
       (-h) --help                  show this help (see below for -h comment)

       Rsync can also be run as a daemon, in which case the following options are accepted:

            --daemon                run as an rsync daemon
            --address=ADDRESS       bind to the specified address
            --bwlimit=KBPS          limit I/O bandwidth; KBytes per second
            --config=FILE           specify alternate rsyncd.conf file
            --no-detach             do not detach from the parent
            --port=PORT             listen on alternate port number
            --log-file=FILE         override the "log file" setting
            --log-file-format=FMT   override the "log format" setting
            --sockopts=OPTIONS      specify custom TCP options
        -v, --verbose               increase verbosity
        -4, --ipv4                  prefer IPv4
        -6, --ipv6                  prefer IPv6
        -h, --help                  show this help (if used after --daemon)