1. 描述
rsync（remote sync）是一个在 Unix 和类 Unix 系统下广泛使用的命令行工具，用于文件和目录之间的高效同步和备份。它的主要特点包括：
增量传输：rsync 可以仅传输文件的变化部分，而不是每次都传输整个文件。这使得它在同步大量数据时效率非常高。
支持远程同步：rsync 可以在本地和远程主机之间同步文件，可以通过 SSH 或 RSH 等协议进行安全的远程同步。
保留文件属性：rsync 可以保留文件的权限、所有者、时间戳等属性。
灵活的过滤选项：rsync 允许用户通过各种选项和模式来过滤文件和目录，可以排除或包含特定的文件类型、文件名等。
断点续传：如果同步过程中中断，rsync 可以在下一次运行时继续未完成的同步，而不需要重新开始。
2. 语法
rsync [选项] 源目录/文件 目标目录/文件
Usage: rsync [OPTION]... SRC [SRC]... DEST
or rsync [OPTION]... SRC [SRC]... [USER@]HOST:DEST
or rsync [OPTION]... SRC [SRC]... [USER@]HOST::DEST
or rsync [OPTION]... SRC [SRC]... rsync://[USER@]HOST[:PORT]/DEST
or rsync [OPTION]... [USER@]HOST:SRC [DEST]
or rsync [OPTION]... [USER@]HOST::SRC [DEST]
or rsync [OPTION]... rsync://[USER@]HOST[:PORT]/SRC [DEST]
The ':' usages connect via remote shell, while '::' & 'rsync://' usages connect
to an rsync daemon, and require SRC or DEST to start with a module name.
Options
-v, --verbose increase verbosity
--info=FLAGS fine-grained informational verbosity
--debug=FLAGS fine-grained debug verbosity
--msgs2stderr special output handling for debugging
-q, --quiet suppress non-error messages
--no-motd suppress daemon-mode MOTD (see manpage 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 set backup suffix (default ~ w/o --backup-dir)
-u, --update skip files that are newer on the receiver
--inplace update destination files in-place (SEE MAN PAGE)
--append append data onto shorter files
--append-verify like --append, but with old data in file checksum
-d, --dirs transfer directories without recursing
-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 source tree
--munge-links munge symlinks to make them safer (but unusable)
-k, --copy-dirlinks transform symlink to a 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 the file's executability
--chmod=CHMOD affect file and/or directory permissions
-A, --acls preserve ACLs (implies --perms)
-X, --xattrs preserve extended attributes
-o, --owner preserve owner (super-user only)
-g, --group preserve group
--devices preserve device files (super-user only)
--copy-devices copy device contents as regular file
--specials preserve special files
-D same as --devices --specials
-t, --times preserve modification times
-O, --omit-dir-times omit directories from --times
-J, --omit-link-times omit symlinks from --times
--super receiver attempts super-user activities
--fake-super store/recover privileged attrs using xattrs
-S, --sparse turn sequences of nulls into sparse blocks
--preallocate allocate dest files before writing them
-n, --dry-run perform a trial run with no changes made
-W, --whole-file copy files whole (without delta-xfer algorithm)
--checksum-choice=STR choose the checksum algorithms
-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 the remote machine
--existing skip creating new files on receiver
--ignore-existing skip updating files that already exist on receiver
--remove-source-files sender removes synchronized files (non-dirs)
--del an alias for --delete-during
--delete delete extraneous files from destination dirs
--delete-before receiver deletes before transfer, not during
--delete-during receiver deletes during the transfer
--delete-delay find deletions during, delete after
--delete-after receiver deletes after transfer, not during
--delete-excluded also delete excluded files from destination dirs
--ignore-missing-args ignore missing source args without error
--delete-missing-args delete missing source args from destination
--ignore-errors delete even if there are I/O errors
--force force deletion of directories 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 transfer's end
-m, --prune-empty-dirs prune empty directory chains from the file-list
--numeric-ids don't map uid/gid values by user/group name
--usermap=STRING custom username mapping
--groupmap=STRING custom groupname mapping
--chown=USER:GROUP simple username/groupname mapping
--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 in size and mod-time
-M, --remote-option=OPTION send OPTION to the remote side only
--size-only skip files that match in size
-@, --modify-window=NUM set the accuracy for mod-time comparisons
-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 destination 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 a suffix in LIST
-C, --cvs-exclude auto-ignore files 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; only wildcard special-chars
--trust-sender trust the remote sender's file list
--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=RATE limit socket I/O bandwidth
--stop-at=y-m-dTh:m Stop rsync at year-month-dayThour:minute
--time-limit=MINS Stop rsync after MINS minutes have elapsed
--outbuf=N|L|B set output buffering to None, Line, or Block
--write-batch=FILE write a batched update to FILE
--only-write-batch=FILE like --write-batch but w/o updating destination
--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)
--noatime do not alter atime when opening source files
-4, --ipv4 prefer IPv4
-6, --ipv6 prefer IPv6
--version print version number
(-h) --help show this help (-h is --help only if used alone)
3. 参数
一些常用选项包括：
-a, --archive：归档模式，保留所有文件属性。-v, --verbose：详细输出。-r, --recursive：递归地同步目录。-z, --compress：使用压缩传输数据，可以减少网络带宽。-e, --rsh=COMMAND：指定远程 shell 程序（例如 SSH）。--delete：删除目标中不在源中的文件。--exclude=PATTERN：排除符合指定模式的文件或目录。
4. 例子
例如，要将本地目录 /local/source 同步到远程主机的 /remote/destination 目录，可以使用如下命令：
rsync -avz /local/source/ user@remote:/remote/destination/
这将使用归档模式同步 /local/source 目录到远程主机上的 /remote/destination 目录，通过 SSH 进行安全传输，并且启用了数据压缩。