如何防止 MySQL 的 ibdata1 文件过大

Posted 2023-04-19

参考技术A 1）备份数据库
备份全部数据库，执行命令
#mysqldump -q -uroot -ppassword --add-drop-table --all-databases >/home/backup/all.sql
做完此步后，停止数据库服务。
#service mysqld stop

2）找到my.ini或my.cnf文件
linux下执行
# /usr/libexec/mysqld --verbose --help | grep -A 1 'Default options'
Default options are read from the following files in the given order:
/etc/mysql/my.cnf /etc/my.cnf ~/.my.cnf
windows环境下可以：
mysqld --verbose --help > mysqlhelp.txt
notepad mysqlhelp.txt
在里面查找Default options，可以看到查找my.ini的顺序，以找到真实目录

3）修改mysql配置文件
打开my.ini或my.cnf文件
[mysqld]下增加下面配置
innodb_file_per_table=1
验证配置是否生效，可以重启mysql后,执行
#service mysqld restart
#mysql -uroot -ppassword
mysql> show variables like '%per_table%';
+-----------------------+-------+
| Variable_name | Value |
+-----------------------+-------+
| innodb_file_per_table | ON |
+-----------------------+-------+
1 row in set (0.00 sec)

mysql>

看看innodb_file_per_table变量是否为ON

MySQL ibdata1文件迁移

目的：主机系统/var目录快满了，经查询最大的文件是mysql的ibdata1文件，有17G大小，故需要迁移这个文件到其他目录下，以释放/var目录空间。

1.先备份下数据库是个好习惯

# mysqldump -q -uuser -ppassword --add-drop-table --all-databases > /usr2/backup/mysql_1013.sql

2.关闭mysql服务

# /etc/init.d/mysqld stop
停止 mysqld： [确定]
# /etc/init.d/mysqld status
mysqld 已停

3.移动ibdata1及其同目录下的文件，从/var/lib/mysql移动到/usr2/mysql

# pwd
/var/lib/mysql
# ls -lh
总用量 17G
-rw-rw---- 1 mysql mysql  17G 10月 13 10:23 ibdata1
-rw-rw---- 1 mysql mysql 5.0M 10月 13 10:23 ib_logfile0
-rw-rw---- 1 mysql mysql 5.0M 10月 13 10:23 ib_logfile1
drwx------ 2 mysql mysql 4.0K 2月  19 2014 mysql
srwxrwxrwx 1 mysql mysql    0 10月 13 10:23 mysql.sock
drwx------ 2 mysql mysql 4.0K 2月  19 2014 test
drwx------ 2 mysql mysql 4.0K 2月  26 2014 zabbix

# mkdir /usr2/mysql
# chown mysql:mysql /usr2/mysql

# su - mysql
$id
uid=27(mysql) gid=27(mysql) 组=27(mysql)
$ mv /var/lib/mysql/* /usr2/mysql/
$

4.修改mysql配置文件/etc/my.cnf,修改datadir和socket路径指向

修改前：
# more /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

修改后：
# more /etc/my.cnf
[mysqld]
datadir=/usr2/mysql
socket=/usr2/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

5.启动mysql服务

# /etc/init.d/mysqld start
正在启动 mysqld： [确定]
# /etc/init.d/mysqld status
mysqld (pid  11907) 正在运行...

6.连接mysql，根据报错提示创建mysql.sock的软连接，验证库表数据，完成迁移工作。

# mysql -uuser -ppassword
ERROR 2002 (HY000): Can‘t connect to local MySQL server through socket ‘/var/lib/mysql/mysql.sock‘ (2)

# ln -s /usr2/mysql/mysql.sock /var/lib/mysql/mysql.sock

# mysql -uuser -ppassword
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 21
Server version: 5.1.66 Source distribution

Copyright (c) 2000, 2012, 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> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| test               |
| zabbix             |
+--------------------+
3 rows in set (0.00 sec)

mysql> use zabbix
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_zabbix      |
+-----------------------+
| acknowledges          |
| actions               |
| alerts                |
……