mysql参数文件

windows平台下，一般在：
WINDIR\my.ini c:\my.ini  INSTALLDIR\my.ini
linux平台，
/etc/my.cnf  /etc/mysql/my.cnf  SYSCONFDIR/my.cnf  $MYSQL_HOME/my.cnf  ~/.my.cnf
另外有几个预设的参数文件，路径可能不一样：
[root@n1 ~]# ls /usr/share/mysql/*.cnf -l
-rw-r--r--. 1 root root  4688 May 11 14:31 /usr/share/mysql/my-huge.cnf
-rw-r--r--. 1 root root 19751 May 11 14:31 /usr/share/mysql/my-innodb-heavy-4G.cnf
-rw-r--r--. 1 root root  4662 May 11 14:31 /usr/share/mysql/my-large.cnf
-rw-r--r--. 1 root root  4673 May 11 14:31 /usr/share/mysql/my-medium.cnf
-rw-r--r--. 1 root root  2441 May 11 14:31 /usr/share/mysql/my-small.cnf
其中，小，中，大，巨分别代表不同规模。
对于参数文件，可以查询到：
which mysql

/usr/bin/mysql --verbose --help | grep -C 4 'Default options'

一些参数：
[]命令行工具
log-error 错误日志文件
log_slow_queries 满查询日志路径
long_query_time 满查询日志时间，默认是10s 说明：满查询日志可以实时修改，set GLOBAL slow_query_log='OFF'|'ON'
否则要重启service mysql restart | systemctl restart mysql.service(对应RHEl7以上)
general_log_file 一般查询日志路径
general_log 一般日志开启关闭表示OFF或者ON,set GLOBAL general_log='OFF'|'ON'

也可以在命令行下查看：

show variables like '%log%'

mysql> show variables like '%log%'
    -> ;
+-----------------------------------------+---------------------------------+
| Variable_name                           | Value                           |
+-----------------------------------------+---------------------------------+
| back_log                                | 50                              |
| binlog_cache_size                       | 32768                           |
| binlog_direct_non_transactional_updates | OFF                             |
| binlog_format                           | STATEMENT                       |
| expire_logs_days                        | 0                               |
| general_log                             | OFF                             |
| general_log_file                        | /var/run/mysqld/mysqld.log      |
| innodb_flush_log_at_trx_commit          | 1                               |
| innodb_locks_unsafe_for_binlog          | OFF                             |
| innodb_log_buffer_size                  | 1048576                         |
| innodb_log_file_size                    | 5242880                         |
| innodb_log_files_in_group               | 2                               |
| innodb_log_group_home_dir               | ./                              |
| innodb_mirrored_log_groups              | 1                               |
| log                                     | OFF                             |
| log_bin                                 | OFF                             |
| log_bin_trust_function_creators         | OFF                             |
| log_bin_trust_routine_creators          | OFF                             |
| log_error                               | /var/log/mysqld.log             |
| log_output                              | FILE                            |
| log_queries_not_using_indexes           | OFF                             |
| log_slave_updates                       | OFF                             |
| log_slow_queries                        | OFF                             |
| log_warnings                            | 1                               |
| max_binlog_cache_size                   | 18446744073709547520            |
| max_binlog_size                         | 1073741824                      |
| max_relay_log_size                      | 0                               |
| relay_log                               |                                 |
| relay_log_index                         |                                 |
| relay_log_info_file                     | relay-log.info                  |
| relay_log_purge                         | ON                              |
| relay_log_space_limit                   | 0                               |
| slow_query_log                          | OFF                             |
| slow_query_log_file                     | /var/run/mysqld/mysqld-slow.log |
| sql_log_bin                             | ON                              |
| sql_log_off                             | OFF                             |
| sql_log_update                          | ON                              |
| sync_binlog                             | 0                               |

+-----------------------------------------+--------------------

在mysql8中可以看到配置文件位置：

mysql> SELECT t1.*, VARIABLE_VALUE 
    ->        FROM performance_schema.variables_info t1 
    ->        JOIN performance_schema.global_variables t2 
    ->          ON t2.VARIABLE_NAME=t1.VARIABLE_NAME
    ->       WHERE t1.VARIABLE_NAME LIKE 'max_connections'\G
*************************** 1. row ***************************
  VARIABLE_NAME: max_connections
VARIABLE_SOURCE: GLOBAL
  VARIABLE_PATH: /etc/my.cnf
      MIN_VALUE: 1
      MAX_VALUE: 100000
       SET_TIME: NULL
       SET_USER: NULL
       SET_HOST: NULL
 VARIABLE_VALUE: 500
1 row in set (0.00 sec)

mysql> status
--------------
./mysql  Ver 8.0.11 for linux-glibc2.12 on x86_64 (MySQL Community Server - GPL)

Connection id:          22
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         8.0.11 MySQL Community Server - GPL
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    utf8mb4
Db     characterset:    utf8mb4
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
UNIX socket:            /tmp/mysql.sock
Uptime:                 3 min 28 sec

Threads: 4  Questions: 644  Slow queries: 0  Opens: 346  Flush tables: 2  Open tables: 322  Queries per second avg: 3.096
--------------

其中VARIABLE_SOURCE代表最近一次修改位置

参考：https://dev.mysql.com/doc/refman/8.0/en/variables-info-table.html