mysqldump是mysql的逻辑备份恢复工具，可以只备份某个表，某个库或者整个数据库。为了保证数据的一致性，备份的时候会加写锁，所以一定要在系统闲的时候用。
语法：
[root@D2-LZY245 ~]# mysqldump
Usage: mysqldump [OPTIONS] database [tables]
OR mysqldump [OPTIONS] --databases [OPTIONS] DB1 [DB2 DB3...]
OR mysqldump [OPTIONS] --all-databases [OPTIONS]
For more options, use mysqldump –help

备份test1库：
[root@D2-LZY245 ~]# mysqldump -uroot -p123456 test1 > test1_bk.sql

查看生成的备份文件：
[root@D2-LZY245 ~]# mysqldump -uroot -p123456 test1 > test1_bk.sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@D2-LZY245 ~]# cat test1_bk.sql
-- MySQL dump 10.13 Distrib 5.7.15, for linux-glibc2.5 (x86_64)
--
-- Host: localhost Database: test1
-- ------------------------------------------------------
-- Server version 5.7.15

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
/*!40103 SET TIME_ZONE='+00:00' */;
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

--
-- Table structure for table `emp`
--

DROP TABLE IF EXISTS `emp`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `emp` (
`employee_id` int(10) DEFAULT NULL,
`first_name` varchar(50) DEFAULT NULL,
`last_name` varchar(50) DEFAULT NULL,
`salary` decimal(10,2) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `emp`
--

LOCK TABLES `emp` WRITE;
/*!40000 ALTER TABLE `emp` DISABLE KEYS */;
INSERT INTO `emp` VALUES (100,'Steven','King',24000.00),(101,'Neena','Kochhar',17000.00),(102,'Lex','De Haan',17000.00),(103,'Alexander','Hunold',9000.00),(104,'Bruce','Ernst',6000.00),(105,'David','Austin',4800.00),(106,'Valli','Pataballa',4800.00),(107,'Diana','Lorentz',4200.00),(108,'Nancy','Greenberg',12008.00),(109,'Daniel','Faviet',9000.00),(110,'John','Chen',8200.00);
/*!40000 ALTER TABLE `emp` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `emp1`
--

DROP TABLE IF EXISTS `emp1`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `emp1` (
`employee_id` int(10) DEFAULT NULL,
`first_name` varchar(50) DEFAULT NULL,
`last_name` varchar(50) DEFAULT NULL,
`salary` decimal(10,2) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `emp1`
--

LOCK TABLES `emp1` WRITE;
/*!40000 ALTER TABLE `emp1` DISABLE KEYS */;
INSERT INTO `emp1` VALUES (100,'Steven','King',24000.00),(101,'Neena','Kochhar',17000.00),(102,'Lex','De Haan',17000.00),(103,'Alexander','Hunold',9000.00),(104,'Bruce','Ernst',6000.00),(105,'David','Austin',4800.00),(106,'Valli','Pataballa',4800.00),(107,'Diana','Lorentz',4200.00),(108,'Nancy','Greenberg',12008.00),(109,'Daniel','Faviet',9000.00),(110,'John','Chen',8200.00);
/*!40000 ALTER TABLE `emp1` ENABLE KEYS */;
UNLOCK TABLES;
/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

-- Dump completed on 2017-05-26 18:32:51

备份文件实际上就是SQL脚本，先是设置参数，如果表存在则删除表，然后创建表，锁表，执行插入语句，解锁。恢复的时候执行这个SQL脚本就好了。执行脚本有2种方式，一种是重定向，一种是使用source。

重定向方式：
mysql> create database test2;
Query OK, 1 row affected (0.00 sec)
＃创建一个数据库test2，恢复到test2。

[root@D2-LZY245 ~]# mysql -uroot -p123456 test2 < test1_bk.sql

查看确认：
mysql> use test2
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show tables;
+-----------------+
| Tables_in_test2 |
+-----------------+
| emp |
| emp1 |
+-----------------+
2 rows in set (0.00 sec)

source方式：
mysql> create database test3;
Query OK, 1 row affected (0.00 sec)

mysql> use test3;
Database changed

mysql> source /root/test1_bk.sql

mysql> show tables;
+-----------------+
| Tables_in_test3 |
+-----------------+
| emp |
| emp1 |
+-----------------+
2 rows in set (0.00 sec)

这两种方式是有区别的，使用重定向方式，如果有错误会直接退出，不会执行后续的语句，而使用source方式则会跳过错误的地方，继续执行后续的语句。