修改ibdata1大小的验证以及如何使用mysqld_multi管理多实例

修改ibdata1大小的验证

ibdata是共享表空间，在MySQL初始化的时候就生成了。

但很多童鞋会看到网上各种大神的调优建议，在MySQL已经初始化的情况下，修改配置文件中innodb_data_file_path=ibdata1:12M:autoextend。导致MySQL启动的时候报错。

下面来模拟一下：

原来的ibdata1大小为12M

# ll -h /sales3306/mysql/data/ibdata1
-rw-rw----.  mysql mysql 12M Mar  : /sales3306/mysql/data/ibdata1

修改配置文件中的innodb_data_file_path参数，调整其大小

innodb_data_file_path=ibdata1:20M:autoextend

重启数据库服务

启动数据库的过程中没有报错，但就是没有起来，查看日志信息

[ERROR] InnoDB: auto-extending data file /sales3306/mysql/data/ibdata1 is of a different size  pages (rounded down to MB) than specified in the .cnf file: initial  pages, max  (relevant if non-zero) pages!

报错信息其实很明显，ibdata1实际大小和配置文件中指定的大小不一致。

遇到这种问题，如何修复呢？

其实，只需将该参数设置为等于或者小于其实际大小。

关于等于，其实不难理解，毕竟要吻合，那小于又为什么可以呢？关键在于该参数后面的autoextend选项，所以实际值比初始值大很正常。当然小于的情况只适用于带有autoextend选项的表空间，MySQL可指定多个表空间，但只有最后一个才能指定该选项。

获取其实际大小，有两种方式，

一是通过ls -l查看其具体大小，可直接写12582912（12M）

二是通过错误日志的报错信息，譬如上面很容易算出其实际大小为768*16/1024=12M

当然，如果默认的共享表空间体积太大了，可新增一个表空间

innodb_data_file_path=ibdata1:12M;ibdata2:20M:autoextend

注意：共享表空间，即便把数据清理掉后，也不会回收空间，只能迁移数据，重新初始化。

mysqld_multi的使用

1. 在执行mysqld_multi时报以下错误：

/usr/local/mysql/bin/mysqld_multi --defaults-file=/root/multi.cnf report
WARNING: my_print_defaults command not found.
Please make sure you have this command available and
in your path. The command is available from the latest
MySQL distribution.
ABORT: Can't find command 'my_print_defaults'.
This command is available from the latest MySQL
distribution. Please make sure you have the command
in your PATH.

解决方法：

在/etc/profile中添加如下内容：

export PATH=$PATH:/usr/local/mysql/bin/

并使其生效 source /etc/profile

2. 启动失败，通过查看mysqld_multi的错误日志/usr/local/mysql/multi.log

有如下报错信息：

Starting MySQL servers

 :: mysqld_safe Logging to '/var/log/mariadb/mariadb.log'.
touch: cannot touch ‘/var/log/mariadb/mariadb.log’: No such file or directory
chmod: cannot access ‘/var/log/mariadb/mariadb.log’: No such file or directory
touch: cannot touch ‘/var/log/mariadb/mariadb.log’: No such file or directory
chown: cannot access ‘/var/log/mariadb/mariadb.log’: No such file or directory
 :: mysqld_safe Logging to '/sales3307/mysql/log/.err'.
 :: mysqld_safe Starting mysqld daemon with databases from /sales3306/mysql/data
/usr/local/mysql/bin/mysqld_safe: line : /var/log/mariadb/mariadb.log: No such file or directory
/usr/local/mysql/bin/mysqld_safe: line : /var/log/mariadb/mariadb.log: No such file or directory
touch: cannot touch ‘/var/log/mariadb/mariadb.log’: No such file or directory
chown: cannot access ‘/var/log/mariadb/mariadb.log’: No such file or directory
chmod: cannot access ‘/var/log/mariadb/mariadb.log’: No such file or directory
 :: mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
/usr/local/mysql/bin/mysqld_safe: line : /var/log/mariadb/mariadb.log: No such file or directory
 :: mysqld_safe Starting mysqld daemon with databases from /sales3307/mysql/data
 :: mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
mysqld_multi log file version 2.16; run: Sat Jan  :: 

。。。怎么会出现mariadb的信息，这个跟我的操作系统有关，CentOS 7，默认的数据库是Mariadb，而不是MysQL。

失败原因：

没有指定错误日志

指定错误日志后，log-error=/sales3307/mysql/log/error.log

重新启动，又报如下错误：

-- ::  [ERROR] /usr/local/mysql/bin/mysqld: Can't create/write to file '/var/run/mariadb/mariadb.pid' (Errcode: 2 - No such file or directory)
-- ::  [ERROR] Can't start server: can't create PID file: No such file or directory
 :: mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended

失败原因：没有指定pid文件

指定pid文件的路径

pid-file=/sales3307/mysql/run/mysqld.pid

重新启动，终于启动成功

# mysqld_multi --defaults-file=/root/multi.cnf report
Reporting MySQL servers
MySQL server from group: mysqld3306 is running
MySQL server from group: mysqld3307 is running

最后贴一下配置文件：

mysqld的部分没有贴，这块配置是公用的

[mysqld_multi]
mysqld     = /usr/local/mysql/bin/mysqld_safe
mysqladmin = /usr/local/mysql/bin/mysqladmin
#用来做关闭mysql使用
user = root
log=/usr/local/mysql/multi.log
##password=''

[mysqld3306]
port=
socket=/sales3306/mysql/run/mysql.sock
datadir=/sales3306/mysql/data
server-id=
log-bin=/sales3306/mysql/log/mysql-bin
tmpdir=/sales3306/mysql/tmp/
innodb_log_group_home_dir = /sales3306/mysql/data
innodb_buffer_pool_size=200M
log-error=/sales3306/mysql/log/error.log
pid-file=/sales3306/mysql/run/mysqld.pid

[mysqld3307]
port=
socket=/sales3307/mysql/run/mysql.sock
datadir=/sales3307/mysql/data
server-id=
log-bin=/sales3307/mysql/log/mysql-bin
tmpdir=/sales3307/mysql/tmp/
innodb_log_group_home_dir = /sales3307/mysql/data
innodb_buffer_pool_size=100M
log-error=/sales3307/mysql/log/error.log
pid-file=/sales3307/mysql/run/mysqld.pid

注意：如果mysqld不是在/usr/local/mysql下，则在每个实例下面还需要添加basedir变量。

在折腾过程中还是蛮多坎坷的，结论就是很个性化的定制，譬如socket，log-error，pid-file都要指定各自的路径。不然启动过程中，系统会按默认的来，多实例都按默认的来，会起冲突的。但整个排错过程还是蛮简单的，不是看mysqld_multi的错误日志，就是实例本身的日志。

下面演示一下，mysqld_multi的用法：

[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf stop

[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf report
Reporting MySQL servers
MySQL server from group: mysqld3306 is not running
MySQL server from group: mysqld3307 is not running
[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf report
Reporting MySQL servers
MySQL server from group: mysqld3306 is not running
[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf start 3306

[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf report
Reporting MySQL servers
MySQL server from group: mysqld3306 is running
MySQL server from group: mysqld3307 is not running

在上述[mysqld_multi]的配置中，有个user和password，这个是用来执行mysqladmin关闭程序的。

有时候，用root权限太大，且密码以明文的方式暴露存在安全风险。

虽然mysqld_multi支持--password选项，但如果两个实例的密码不一样，又如何同时关闭实例呢？

可为两个实例创建同名账户，只赋予shutdown权限，这样可解决上述的困扰。

mysql>  grant shutdown on *.* to 'multiadmin'@'localhost' identified by '';
Query OK,  rows affected (0.00 sec)

mysql> flush privileges;
Query OK,  rows affected (0.00 sec)

-----------------------------------------

最后验证的时候，发现直接将password添加到[mysqld_multi]中，并不能关闭实例

# grep "password" -B  multi.cnf
[mysqld_multi]
mysqld     = /usr/local/mysql/bin/mysqld_safe
mysqladmin = /usr/local/mysql/bin/mysqladmin
#用来做关闭mysql使用
user =multiadmin
password=

[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf start
[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf report
Reporting MySQL servers
MySQL server from group: mysqld3306 is running
MySQL server from group: mysqld3307 is running
[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf stop
[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf report
Reporting MySQL servers
MySQL server from group: mysqld3306 is running
MySQL server from group: mysqld3307 is running
[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf --password= stop
[root@spark01 ~]# mysqld_multi --defaults-file=/root/multi.cnf report
Reporting MySQL servers
MySQL server from group: mysqld3306 is not running
MySQL server from group: mysqld3307 is not running

直接使用stop并不能关闭实例，但是在客户端指定password却又可以，用mysqladmin关闭又没问题。

直接使用stop关闭，multi日志报如下信息：

Warning: Using a password on the command line interface can be insecure.
^G/usr/local/mysql/bin/mysqladmin: connect to server at 'localhost' failed
error: 'Access denied for user 'multiadmin'@'localhost' (using password: YES)'

当然，[mysqld_multi]中除了用mysqld_safe启动mysql实例外，也可直接通过mysqld，这时[mysqld3306]，[mysqld3307]中需指定user=mysql。

------------------------------------------------

在验证的过程中，发现给multiadmin如下授权

GRANT ALL PRIVILEGES ON *.* TO 'multiadmin'@'%' IDENTIFIED BY PASSWORD

%并不包括localhost

验证如下：

mysql> select user,host,password from mysql.user;
+------------+-----------+-------------------------------------------+
| user       | host      | password                                  |
+------------+-----------+-------------------------------------------+
| root       | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| root       | spark01   |                                           |
| root       | 127.0.0.1 |                                           |
| root       | ::1       |                                           |
|            | localhost |                                           |
|            | spark01   |                                           |
| multiadmin | %         | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+------------+-----------+-------------------------------------------+

在本机用multiadmin登录

# mysql --socket=/sales3307/mysql/run/mysql.sock -umultiadmin -p123456
Warning: Using a password on the command line interface can be insecure.
ERROR 1045 (28000): Access denied for user 'multiadmin'@'localhost' (using password: YES)

但是不输入密码却又能登录，只是没有任何权限

[root@spark01 ~]# mysql --socket=/sales3307/mysql/run/mysql.sock -umultiadmin
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 5.6.28-log MySQL Community Server (GPL)

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> \s
--------------
mysql  Ver 14.14 Distrib 5.6.28, for linux-glibc2.5 (x86_64) using  EditLine wrapper

Connection id:        8
Current database:
Current user:        multiadmin@localhost
SSL:            Not in use
Current pager:        stdout
Using outfile:        ''
Using delimiter:    ;
Server version:        5.6.28-log MySQL Community Server (GPL)
Protocol version:    10
Connection:        Localhost via UNIX socket
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    utf8
Conn.  characterset:    utf8
UNIX socket:        /sales3307/mysql/run/mysql.sock
Uptime:            32 min 17 sec

Threads: 1  Questions: 22  Slow queries: 0  Opens: 74  Flush tables: 1  Open tables: 67  Queries per second avg: 0.011
--------------

mysql> select user();
+----------------------+
| user()               |
+----------------------+
| multiadmin@localhost |
+----------------------+
1 row in set (0.00 sec)

mysql> select user,host from mysql.users;
ERROR 1142 (42000): SELECT command denied to user ''@'localhost' for table 'users'

这个其实与上面权限表中的user为空，host为localhost有关。

只要是从本地登录，不管你指定任何权限表之外的用户，都可以登录，譬如hello用户在权限表中并不存在，却依然可以登录，就是拜user为空，host为localhost所赐。

[root@spark01 ~]# mysql --socket=/sales3307/mysql/run/mysql.sock -uhello
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 5.6.28-log MySQL Community Server (GPL)

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

所以，作为mysql安全加固的一部分，这些账号都可以删除的。

总结：如果multiadmin要从本地登录，必须授予localhost的登录权限，%并不包含localhost。

grant all privileges on *.* to 'multiadmin'@'localhost' identified by '';