a fast, versatile, remote (and local) file-copying tool
|
-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.
|
-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 options will give you information on what files are being
skipped and slightly more information at the end. More than two -v options should only be used if
you are debugging rsync.
Note that the names of the transferred files that are output are done using a default --out-format
of "%n%L", which tells you just the name of the file and, if the item is a link, where it points.
At the single -v level of verbosity, this does not mention when a file gets its attributes
changed. If you ask for an itemized list of changed attributes (either --itemize-changes or
adding "%i" to the --out-format setting), the output (on the client) increases to mention all
items that are changed in any way. See the --out-format option for more details.
|
-z, --compress
With this option, rsync compresses the file data as it is sent to the destination machine, which
reduces the amount of data being transmitted -- something that is useful over a slow connection.
Note that this option typically achieves better compression ratios than can be achieved by using a
compressing remote shell or a compressing transport because it takes advantage of the implicit
information in the matching data blocks that are not explicitly sent over the connection.
See the --skip-compress option for the default list of file suffixes that will not be compressed.
|
-c, --checksum
This changes the way rsync checks if the files have been changed and are in need of a transfer.
Without this option, rsync uses a "quick check" that (by default) checks if each file’s size and
time of last modification match between the sender and receiver. This option changes this to
compare a 128-bit checksum for each file that has a matching size. Generating the checksums means
that both sides will expend a lot of disk I/O reading all the data in the files in the transfer
(and this is prior to any reading that will be done to transfer changed files), so this can slow
things down significantly.
The sending side generates its checksums while it is doing the file-system scan that builds the
list of the available files. The receiver generates its checksums when it is scanning for changed
files, and will checksum any file that has the same size as the corresponding sender’s file:
files with either a changed size or a changed checksum are selected for transfer.
Note that rsync always verifies that each transferred file was correctly reconstructed on the
receiving side by checking a whole-file checksum that is generated as the file is transferred, but
that automatic after-the-transfer verification has nothing to do with this option’s
before-the-transfer "Does this file need to be updated?" check.
For protocol 30 and beyond (first supported in 3.0.0), the checksum used is MD5. For older
protocols, the checksum used is MD4.
|
-p, --perms
This option causes the receiving rsync to set the destination permissions to be the same as the
source permissions. (See also the --chmod option for a way to modify what rsync considers to be
the source permissions.)
When this option is off, permissions are set as follows:
o Existing files (including updated files) retain their existing permissions, though the
--executability option might change just the execute permission for the file.
o New files get their "normal" permission bits set to the source file’s permissions masked
with the receiving directory’s default permissions (either the receiving process’s umask,
or the permissions specified via the destination directory’s default ACL), and their
special permission bits disabled except in the case where a new directory inherits a setgid
bit from its parent directory.
Thus, when --perms and --executability are both disabled, rsync’s behavior is the same as that of
other file-copy utilities, such as cp(1) and tar(1).
In summary: to give destination files (both old and new) the source permissions, use --perms. To
give new files the destination-default permissions (while leaving existing files unchanged), make
sure that the --perms option is off and use --chmod=ugo=rwX (which ensures that all non-masked
bits get enabled). If you’d care to make this latter behavior easier to type, you could define a
popt alias for it, such as putting this line in the file ~/.popt (the following defines the -Z
option, and includes --no-g to use the default group of the destination dir):
rsync alias -Z --no-p --no-g --chmod=ugo=rwX
You could then use this new option in a command such as this one:
rsync -avZ src/ dest/
(Caveat: make sure that -a does not follow -Z, or it will re-enable the two "--no-*" options
mentioned above.)
The preservation of the destination’s setgid bit on newly-created directories when --perms is off
was added in rsync 2.6.7. Older rsync versions erroneously preserved the three special permission
bits for newly-created files when --perms was off, while overriding the destination’s setgid bit
setting on a newly-created directory. Default ACL observance was added to the ACL patch for rsync
2.6.7, so older (or non-ACL-enabled) rsyncs use the umask even if default ACLs are present. (Keep
in mind that it is the version of the receiving rsync that affects these behaviors.)
|