由于要做一个推荐系统，但是原有的mongodb数据库的样本太少了，

只好从远程主机1复制数据到远程主机2.

这里使用mongodump命令和mongorestore命令。

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~mongodump命令的使用过程。

语法如下：

mongodump -h  dbhost  -d  dbname  -o   dbdirectory

-h: 数据库主机，可以有两种形式

1） 1.2.3.4

2)  1.2.3.3:1234

-d:需要备份的数据库实例。

-o:数据备份的存放位置，命令完成后会在这个目录下存放你指定的数据库实例的备份数据。

好，现在知道原理了，

但是有个问题是，我不想全部复制数据库里的所有集合，

这样会影响服务器的性能，那我只好指定部分集合来导。

OK,搜索具体的参数。。。。。。网上知道了 -c

ok,开始备份。

./mongodump -h XXX.XXX.XXX.XXX:XXX -d  XXX -c XXX   -o XXX

下面是执行过程：

Fri Dec 27 10:30:15.076 DATABASE: XXX to    /usr/local/sbt/data
Fri Dec 27 10:30:15.078     XXX.XXXto /usr/local/sbt/data/XXX/sharings.bson
Fri Dec 27 10:30:18.017         Collection File Writing Progress: 824600/14438822   5%  (objects)
Fri Dec 27 10:30:21.036         Collection File Writing Progress: 1573300/14438822  10% (objects)
Fri Dec 27 10:30:24.019         Collection File Writing Progress: 2347800/14438822  16% (objects)
Fri Dec 27 10:30:27.003         Collection File Writing Progress: 3216800/14438822  22% (objects)
Fri Dec 27 10:30:30.016         Collection File Writing Progress: 4062600/14438822  28% (objects)
Fri Dec 27 10:30:33.000         Collection File Writing Progress: 4928700/14438822  34% (objects)
Fri Dec 27 10:30:36.030         Collection File Writing Progress: 5720900/14438822  39% (objects)
Fri Dec 27 10:30:39.033         Collection File Writing Progress: 6536200/14438822  45% (objects)
Fri Dec 27 10:30:42.007         Collection File Writing Progress: 7300400/14438822  50% (objects)
Fri Dec 27 10:30:45.001         Collection File Writing Progress: 8077500/14438822  55% (objects)
Fri Dec 27 10:30:48.020         Collection File Writing Progress: 8870800/14438822  61% (objects)
Fri Dec 27 10:30:51.024         Collection File Writing Progress: 9628300/14438822  66% (objects)
Fri Dec 27 10:30:54.013         Collection File Writing Progress: 10362100/14438822 71% (objects)
Fri Dec 27 10:30:57.000         Collection File Writing Progress: 11137100/14438822 77% (objects)
Fri Dec 27 10:31:00.029         Collection File Writing Progress: 11901400/14438822 82% (objects)
Fri Dec 27 10:31:03.023         Collection File Writing Progress: 12688300/14438822 87% (objects)
Fri Dec 27 10:31:06.005         Collection File Writing Progress: 13445400/14438822 93% (objects)
Fri Dec 27 10:31:09.039         Collection File Writing Progress: 14251800/14438822 98% (objects)
Fri Dec 27 10:31:09.670          14438822 objects