Mysql数据库无法启动问题的解决方案

问题1:

$ /etc/init.d/mysqld1 status
MySQL is not running, but lock exists

解决方案:

A MySQL crash on Red Hat system resulted with: 

/etc/init.d/mysql status 

coming back with: 

mysql is not running but lock exists 


Solved by removing the lock file: 

rm /var/lock/subsys/mysql 


If this happens again it may also be necessary to remove the pid file from /var/lib/mysql

问题2:

$ /etc/init.d/mysqld1 start
Starting MySQL/data_big/mysql/data1
.Manager of pid-file quit without updating file.           [FAILED]

解决方案:

首先查看mysql日志:

找到mysql安装目录下.err后缀的文件,可以通过 sudo sz *.err 下载下来查看

异常消息如下:

171107 16:56:09 mysqld_safe Starting mysqld daemon with databases from /data_big/mysql/data1
2017-11-07 16:56:10 0 [Warning] 'THREAD_CONCURRENCY' is deprecated and will be removed in a future release.
2017-11-07 16:56:10 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2017-11-07 16:56:10 0 [Note] /usr/local/mysql/bin/mysqld (mysqld 5.6.29-log) starting as process 9060 ...
2017-11-07 16:56:10 9060 [Warning] Using unique option prefix myisam_recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
2017-11-07 16:56:10 9060 [Note] Plugin 'FEDERATED' is disabled.
2017-11-07 16:56:10 9060 [Note] InnoDB: Using atomics to ref count buffer pool pages
2017-11-07 16:56:10 9060 [Note] InnoDB: The InnoDB memory heap is disabled
2017-11-07 16:56:10 9060 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2017-11-07 16:56:10 9060 [Note] InnoDB: Memory barrier is not used
2017-11-07 16:56:10 9060 [Note] InnoDB: Compressed tables use zlib 1.2.3
2017-11-07 16:56:10 9060 [Note] InnoDB: Using Linux native AIO
2017-11-07 16:56:10 9060 [Note] InnoDB: Using CPU crc32 instructions
2017-11-07 16:56:10 9060 [Note] InnoDB: Initializing buffer pool, size = 4.0G
2017-11-07 16:56:10 9060 [Note] InnoDB: Completed initialization of buffer pool
2017-11-07 16:56:10 9060 [Note] InnoDB: Highest supported file format is Barracuda.
2017-11-07 16:56:10 9060 [Note] InnoDB: The log sequence numbers 1600614 and 1600614 in ibdata files do not match the log sequence number 15629474422 in the ib_logfiles!
2017-11-07 16:56:10 9060 [Note] InnoDB: Database was not shutdown normally!
2017-11-07 16:56:10 9060 [Note] InnoDB: Starting crash recovery.
2017-11-07 16:56:10 9060 [Note] InnoDB: Reading tablespace information from the .ibd files...
2017-11-07 16:56:10 9060 [ERROR] InnoDB: Attempted to open a previously opened tablespace. Previous tablespace mysql/slave_master_i

仔细查看,发现日志消息中给出了三种解决方案:

To fix the problem and start mysqld:
InnoDB: 1) If there is a permission problem in the file and mysqld cannot
InnoDB: open the file, you should modify the permissions.
InnoDB: 2) If the table is not needed, or you can restore it from a backup,
InnoDB: then you can remove the .ibd file, and InnoDB will do a normal
InnoDB: crash recovery and ignore that table.
InnoDB: 3) If the file system or the disk is broken, and you cannot remove
InnoDB: the .ibd file, you can set innodb_force_recovery > 0 in my.cnf
InnoDB: and force InnoDB to continue crash recovery here.
171107 16:56:10 mysqld_safe mysqld from pid file /data_big/mysql/data1/iZwz9istfz0zvx3yuaf6tqZ.pid ended

拓展: 看看日志文件的大小 看看my.cnf 设定的日志文件大小 看看磁盘使用百分比 备份并清除日志文件吧！ 再重启试试看

这个命令可以查看默认my.cnf文件的位置

mysql --help|grep 'my.cnf'