今天公司很久以前的一台WDCP集成的Web服务出现了问题，打开网页显示“无法连接mysql，请检查mysql是否已启动及用户密码是否配置正确”
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?????????????????（上图为服务器故障时Web访问报错信息）
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????在网上找了三个小时的资料，找到了很多遇到该问题的朋友，并且只要是数据库连接不正常的或者数据库无法正常启动的，全都会报这个错误，下面是我的解决方法：
1、检查服务运行状态
[[email protected] etc]# service mysqld status
?mysql is not running.
#mysql服务并未运行
[[email protected] etc]# service mysqld restart
?ERROR! MySQL manager or server PID file could not be found!
Starting MySQL. ERROR! Manager of pid-file quit without updating file.
#试图重启服务，结果报错
[[email protected] etc]# cat /www/wdlinux/mysql-5.1.69/var/WDCP.err
查看WDCP的错误日志
? ? 171209 16:10:02 mysqld_safe mysqld from pid file /www/wdlinux/mysql-5.1.69/var/WDCP.pid ended
????171209 16:12:25 mysqld_safe Starting mysqld daemon with databases from /www/wdlinux/mysql-5.1.69/var
????171209 16:12:25 [ERROR] /www/wdlinux/mysql-5.1.69/libexec/mysqld: unknown variable ‘innodb_additional_mem_pool_size=16M‘
????171209 16:12:25 [ERROR] Aborting
????#从日志看为止的innodb我觉定把innodb的选项注释掉看一下，结果重启服务报了一个新的错误。
????171209 16:10:02 mysqld_safe mysqld from pid file /www/wdlinux/mysql-5.1.69/var/WDCP.pid ended
????171209 16:12:25 mysqld_safe Starting mysqld daemon with databases from /www/wdlinux/mysql-5.1.69/var
????171209 16:12:25 [ERROR] /www/wdlinux/mysql-5.1.69/libexec/mysqld: unknown variable ‘innodb_additional_mem_pool_size=16M‘
????171209 16:12:25 [ERROR] Aborting
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????171209 16:12:25 [Note] /www/wdlinux/mysql-5.1.69/libexec/mysqld: Shutdown complete
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????171209 16:12:25 mysqld_safe mysqld from pid file /www/wdlinux/mysql-5.1.69/var/WDCP.pid ended
????171209 16:13:32 mysqld_safe Starting mysqld daemon with databases from /www/wdlinux/mysql-5.1.69/var
????171209 16:13:32 [ERROR] /www/wdlinux/mysql-5.1.69/libexec/mysqld: unknown variable ‘innodb_buffer_pool_size=2G‘
????171209 16:13:32 [ERROR] Aborting
????#还是和innodb有关系，决定吧所有的innodb都注销掉！！！? ??
????171209 16:13:32 [Note] /www/wdlinux/mysql-5.1.69/libexec/mysqld: Shutdown complete
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????171209 16:13:32 mysqld_safe mysqld from pid file /www/wdlinux/mysql-5.1.69/var/WDCP.pid ended
????171209 16:14:34 mysqld_safe Starting mysqld daemon with databases from /www/wdlinux/mysql-5.1.69/var
????171209 16:14:35 [ERROR] /www/wdlinux/mysql-5.1.69/libexec/mysqld: unknown variable ‘innodb_buffer_pool_size=2G‘
????171209 16:14:35 [ERROR] Aborting
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????171209 16:14:35 [Note] /www/wdlinux/mysql-5.1.69/libexec/mysqld: Shutdown complete
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????171209 16:14:35 mysqld_safe mysqld from pid file /www/wdlinux/mysql-5.1.69/var/WDCP.pid ended
? ? #在/www/wdlinux/etc/my.cnf有关innodb的选项全部注释掉
????#innodb_buffer_pool_size = 2G
????#innodb_data_file_path = ibdata1:10M:autoextend
????#innodb_file_io_threads = 4
????#innodb_thread_concurrency = 16
????#innodb_flush_log_at_trx_commit = 1
????#innodb_log_buffer_size = 8M
????#innodb_log_file_size = 256M
????#innodb_log_files_in_group = 3
????#innodb_max_dirty_pages_pct = 90
????#innodb_lock_wait_timeout = 120
????启动mysql服务进行测试：
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????[[email protected] ~]# service mysqld start
????Starting MySQL. SUCCESS!
? ? #mysql启动成功
????具体原因暂时还没找到，主要是因为这不是主要的业务系统，以及该系统是前期开发人员搭建的，所以存在一些问题，此文档仅作为简单记录，查出具体问题后会整理详细文档。