MySQL异常宕机无法启动的处理过程

Database was not shutdown normally!
2021-02-26T21:33:29.691452+08:00 0 [Note] InnoDB: Starting crash recovery.
2021-02-26T21:33:30.287496+08:00 0 [Note] InnoDB: Starting an apply batch of log records to the database...
InnoDB: Progress in percent: 0 1 2 3 4 5 6 7 8 9 10 11 12  #进度到这里自动退出了

innodb_force_recovery可以是设置1-6，数字大的包含数字小的功能，所以我们要从1开始设置来尝试启动mysql
innodb_force_recovery=0，关闭恢复功能 正常启动
innodb_force_recovery=1，即使发现了损坏页面也继续让服务器继续运行，这个选项对于备份或者转存当前数据尤为有用
innodb_force_recovery=2，阻止恢复主线程的运行，如果清除操作会导致服务器挂掉
innodb_force_recovery=3，恢复后不回滚事务
innodb_force_recovery=4，如果插入到缓冲区的合并操作会导致系统崩溃，将不会被执行
innodb_force_recovery=5，启动数据库时，忽略撤消日志
innodb_force_recovery=6，启动数据库时，忽略与恢复相关的前滚日志

#先打开日志
[root@db02 ~]# tail -f /mydata/3306/log/mysql-error.log

#启动了很久显示失败
[root@db02 ~]# /etc/init.d/mysqld restart 
 ERROR! MySQL server PID file could not be found!
Starting MySQL.................................................................................................................................... ERROR! The server quit without updating PID file (/mydata/3306/data/db02.pid).

#查看日志显示已经恢复到百分之百了
2021-02-26T21:40:27.983238+08:00 0 [Note] InnoDB: Starting an apply batch of log records to the database...
InnoDB: Progress in percent: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 2021-02-26T21:41:26.220425+08:00 0 [ERROR] InnoDB: Waited for 10 seconds for 256 pending reads
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99


#再往下翻翻发现错误点----->是因为启用了恢复时启用了 innodb_force_recovery 参数
2021-02-26T21:42:11.303902+08:00 0 [ERROR] InnoDB: innodb_force_recovery is on. We do not allow database modifications by the user. Shut down mysqld and edit my.cnf to set innodb_force_recovery=0
mysqld: Operation not allowed when innodb_forced_recovery > 0.
2021-02-26T21:42:11.306255+08:00 0 [ERROR] Aborting

#关闭innodb_force_recovery 参数
[root@db02 ~]# vim /etc/my.cnf
innodb_force_recovery = 0

[root@db02 ~]# /etc/init.d/mysqld start
Starting MySQL.. SUCCESS!

mysqld_safe --skip-grant-tables --skip-networking &

ps -ef|grep mysql

tail -f /mydata/3306/log/err.log

mysqlcheck -A   --auto-repair  -uroot -p -A

mysqldump -uroot -p -A  -R -E --triggers  >/tmp/dump.sql

mkdir /mydata/3306/data_new

chown -R mysql:mysql  /mydata/3306/data_new

vim /etc/my.cnf
datadir=/mydata/3306/data_new  # 改为新的
# skip_grant_tables  # 注释此选项
# innodb_force_recovery  # 注释此选项

mysqld  --initialize-insecure   --basedir=/mysql/mysql57  --datadir=/mydata/3306/data_new

pkill mysql

/etc/init.d/mysqld start  # 这个文件里要改成新的数据目录名去启动

mysql -uroot -p 

source /tmp/dump.sql
或者
mysql < /tmp/dump.sql

cat >/etc/sysctl.conf<<'EOF'
vm.swappiness=0          # 减少 swap 分区使用
vm.overcommit_memory = 1 # 允许所有内存分配
EOF

# 生效
sysctl -p

# 配置文件永久修改
vim /etc/my.cnf
innodb_buffer_pool_size = 2G  # 将缓冲池配置为系统当前可用内存的 3/4

# 命令行临时修改
set global innodb_buffer_pool_size=(select 2*1024*1024*1024);