linux命令中的cp,【整理】Linux命令中：rsync和cp之间的区别

【背景】

折腾：

期间，通过：

而了解到了rsync的功能：

大概就是，相当于，从源，到目的，拷贝文件，并且可以设置参数，保持很多文件和文件夹的属性。

感觉和cp很类似。

所以想要搞清楚，rsync和cp的区别。

【折腾过程】

1.参考：

的解释是：

其中一人的解释：

对于拷贝文件，实现备份的话，rsync，比cp更好。

因为rsync只拷贝那些改动了的内容。

2.另外的解释，貌似更合理：

rsync未必是最好。取决于实际情况。

比如：

当拷贝的源和目标，内容很大，而差异很小，则用cp -u

会更有效。

3.所以先去看看cp的用法：CLi@PC-CLI-1 ~/develop/buildroot/buildroot-2013.05

$ cp --help

Usage: cp [OPTION]... [-T] SOURCE DEST

or: cp [OPTION]... SOURCE... DIRECTORY

or: cp [OPTION]... -t DIRECTORY SOURCE...

Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.

Mandatory arguments to long options are mandatory for short options too.

-a, --archive same as -dR --preserve=all

--attributes-only don't copy the file data, just the attributes

--backup[=CONTROL] make a backup of each existing destination file

-b like --backup but does not accept an argument

--copy-contents copy contents of special files when recursive

-d same as --no-dereference --preserve=links

-f, --force if an existing destination file cannot be

opened, remove it and try again (redundant if

the -n option is used)

-i, --interactive prompt before overwrite (overrides a previous -n

option)

-H follow command-line symbolic links in SOURCE

-l, --link hard link files instead of copying

-L, --dereference always follow symbolic links in SOURCE

-n, --no-clobber do not overwrite an existing file (overrides

a previous -i option)

-P, --no-dereference never follow symbolic links in SOURCE

-p same as --preserve=mode,ownership,timestamps

--preserve[=ATTR_LIST] preserve the specified attributes (default:

mode,ownership,timestamps), if possible

additional attributes: context, links, xattr,

all

--no-preserve=ATTR_LIST don't preserve the specified attributes

--parents use full source file name under DIRECTORY

-R, -r, --recursive copy directories recursively

--reflink[=WHEN] control clone/CoW copies. See below

--remove-destination remove each existing destination file before

attempting to open it (contrast with --force)

--sparse=WHEN control creation of sparse files. See below

--strip-trailing-slashes remove any trailing slashes from each SOURCE

argument

-s, --symbolic-link make symbolic links instead of copying

-S, --suffix=SUFFIX override the usual backup suffix

-t, --target-directory=DIRECTORY copy all SOURCE arguments into DIRECTORY

-T, --no-target-directory treat DEST as a normal file

-u, --update copy only when the SOURCE file is newer

than the destination file or when the

destination file is missing

-v, --verbose explain what is being done

-x, --one-file-system stay on this file system

--help display this help and exit

--version output version information and exit

By default, sparse SOURCE files are detected by a crude heuristic and the

corresponding DEST file is made sparse as well. That is the behavior

selected by --sparse=auto. Specify --sparse=always to create a sparse DEST

file whenever the SOURCE file contains a long enough sequence of zero bytes.

Use --sparse=never to inhibit creation of sparse files.

When --reflink[=always] is specified, perform a lightweight copy, where the

data blocks are copied only when modified. If this is not possible the copy

fails, or if --reflink=auto is specified, fall back to a standard copy.

The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.

The version control method may be selected via the --backup option or through

the VERSION_CONTROL environment variable. Here are the values:

none, off never make backups (even if --backup is given)

numbered, t make numbered backups

existing, nil numbered if numbered backups exist, simple otherwise

simple, never always make simple backups

As a special case, cp makes a backup of SOURCE when the force and backup

options are given and SOURCE and DEST are the same name for an existing,

regular file.

Report cp bugs to bug-coreutils@gnu.org

GNU coreutils home page:

General help using GNU software:

For complete documentation, run: info coreutils 'cp invocation'

CLi@PC-CLI-1 ~/develop/buildroot/buildroot-2013.05

$

得知-u是update，更新的意思，只更新SOURCE中更新的内容，或者是目标中缺失的文件：

对于文件备份来说，已经足够用了：

每次备份，的确只要备份：

要么是内容更新

要么是原先没有(缺失的)文件

即可。

4.再参考了：

后，更加推荐用rsync了：

rsync可以显示进度条(虽然不是很完美)：对于拷贝大量文件，还是很有用的。

其举了个例子：rsync -a --stats --progress /home/tim/stuff /home/tim/documents

而还支持ssh：rsync -a --stats --progress /home/tim/stuff tim@foo.example.com:/home/tim/

或：rsync -a --stats --progress tim@foo.example.com:/home/tim/stuff /home/tim/

5.另外有空也可以参考：

【总结】

rsync：只拷贝那些更新的文件；

cp -u：也可以实现类似效果；

两者都基本可以满足备份的需求；

只是一般情况下，用rsync做这类备份之类的事情，更多见；

总体来说：

备份文件，更推荐用rsync。