centos8部署MySQL5.7故障集

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在centos8系统上安装MySQL，使用的是centos7上安装MySQL的脚本，出现了以下问题，以做记录：

问题一：日志文件不存在，MySQL无法启动

错误日志：

[root@confluence packages]# /etc/init.d/mysqld restart
 ERROR! MySQL server PID file could not be found!
Starting MySQL.2022-01-15T03:58:44.753030Z mysqld_safe error: log-error set to '/var/log/mariadb/mariadb_error.log', however file don't exists. Create writable for user 'mysql'.
 ERROR! The server quit without updating PID file (/home/confluence/mysql/mysql_data/confluence.pid).

原因和解决方法：

根据日志提示，MySQL无法启动是因为指定的日志文件/var/log/mariadb/mariadb_error.log不存在
touch创建/var/log/mariadb/mariadb_error.log，并修改权限为mysql:mysql，该错误解决。

问题二：/etc/my.cnf文件为空，MySQL无法启动

错误日志：

[root@confluence packages]# /etc/init.d/mysqld start
Starting MySQL.. ERROR! The server quit without updating PID file (/home/confluence/mysql/mysql_data/confluence.pid).
[root@confluence packages]# 

原因和解决方法：

原因是/etc/my.cnf文件是空的，什么配置都没有。
查看/etc/my.cnf，文件没有配置数据目录等信息，文件内容如下：

[root@confluence mysql]# cat /etc/my.cnf
#
# This group is read both both by the client and the server
# use it for options that affect everything
#
[client-server]

#
# include all files from the config directory
#
!includedir /etc/my.cnf.d

[root@confluence mysql]# 

/etc/my.cnf.d目录下只存在client.cnf一个文件，内容也是空的：

[root@confluence mysql]# cat /etc/my.cnf.d/client.cnf 
#
# These two groups are read by the client library
# Use it for options that affect all clients, but not the server
#
[client]
# This group is not read by mysql client library,
# If you use the same .cnf file for MySQL and MariaDB,
# use it for MariaDB-only client options
[client-mariadb]

[root@confluence mysql]# 

把/etc/my.cnf文件补充完整，问题即解决。

问题三：/etc/my.cnf文件权限过大导致MySQL无法启动

错误日志：

[root@confluence etc]# /etc/init.d/mysqld start
my_print_defaults: [Warning] World-writable config file '/etc/my.cnf' is ignored.
Starting MySQL.my_print_defaults: [Warning] World-writable config file '/etc/my.cnf' is ignored.
my_print_defaults: [Warning] World-writable config file '/etc/my.cnf' is ignored.
.. ERROR! The server quit without updating PID file (/home/confluence/mysql/mysql_data/confluence.pid).
[root@confluence etc]# 

原因和解决方法：

原因是因为/etc/my.cnf文件是从其它节点拷贝拷贝过来的，上传后默认的权限过大。把/etc/my.cnf文件的权限改成644，重新启动MySQL则成功。