Ubuntu中MySQL的参数文件my.cnf示例详析

前言

对于mysql的理解，我认为很多性能优化工作、主从主主复制都是在调整参数，来适应不同时期不同数量级的数据。

故，理解透彻my.cnf里的参数是永恒的话题；只有理解透彻了参数设置，才能在某些方面对数据库进行调优。

前几天刚接手一个mysql数据，操作系统为ubuntu 16.04.5 lts，  数据库版本为5.7.23-0ubuntu0.16.04.1（apt方式安装的mysql）。这个操作系统下的mysql的配置文件my.cnf很多地方都让人有点不适应（跟之前的mysql环境有些出入，之前都是维护rhel、centos等操作系统环境下的mysql）。

遂研究总结了一下。具体如下所示：

root@mylnx12:~# find / -name "my.cnf"
/etc/alternatives/my.cnf
/etc/mysql/my.cnf
/var/lib/dpkg/alternatives/my.cnf
root@mylnx12:~# locate my.cnf
/etc/alternatives/my.cnf
/etc/mysql/my.cnf
/etc/mysql/my.cnf.fallback
/var/lib/dpkg/alternatives/my.cnf
root@mylnx12:~# mysql --help | grep my.cnf
      order of preference, my.cnf, $mysql_tcp_port,
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf 
root@mylnx12:~# mysqld --verbose --help | grep -a 1 'default options'
default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf 

从上面这些信息判断，mysql的参数文件为/etc/mysql/my.cnf， 但是其他几个my.cnf又是什么情况呢？

root@mylnx12:~# ls -lrt /etc/alternatives/my.cnf
lrwxrwxrwx 1 root root 20 sep 28 16:28 /etc/alternatives/my.cnf -> /etc/mysql/mysql.cnf

从上面信息可以看出，/etc/alternatives/my.cnf 其实是一个软连接，指向参数文件/etc/mysql/mysql.cnf

root@mylnx12:~# cat /var/lib/dpkg/alternatives/my.cnf
auto
/etc/mysql/my.cnf
 
/etc/mysql/my.cnf.fallback
100
/etc/mysql/mysql.cnf
200

光从上面这些信息，我们还看不出/var/lib/dpkg/alternatives/my.cnf与其它配置文件my.cnf是什么关系。那么我们先来看看参数文件/etc/mysql/my.cnf,从下面信息，可以看出“/etc/mysql/my.cnf”是全局配置，“~/.my.cnf”隐藏文件是个人用户设置.

root@mylnx12:~# cat /etc/mysql/my.cnf
#
# the mysql database server configuration file.
#
# you can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
# 
# one can use all long options that the program supports.
# run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# for explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
 
#
# * important: additional settings that can override those from this file!
#  the files must end with '.cnf', otherwise they'll be ignored.
#
 
!includedir /etc/mysql/conf.d/
!includedir /etc/mysql/mysql.conf.d/

但是/etc/mysql/my.cnf参数文件下面没有任何参数设置，只看到下面两行设置，表示导入这两个目录里面的配置文件。

!includedir /etc/mysql/conf.d/    

#表示包含/etc/mysql/conf.d/这个路径下面的配置文件，前提是必须以为.cnf为后缀

!includedir /etc/mysql/mysql.conf.d/

#表示包含/etc/mysql/mysql.conf.d/这个路径下面的配置文件，前提是必须以为.cnf为后缀

其实mysql的相关配置都位于mysqld.cnf（/etc/mysql/mysql.conf.d/mysqld.cnf）下面。使用相关参数测试了一下，确实都能生效。这种设置确实有点让刚接触的人有点不适应。暂时先总结到此！

root@mylnx12:~# cd /etc/mysql/mysql.conf.d/
root@mylnx12:/etc/mysql/mysql.conf.d# ls -lrt
total 8
-rw-r--r-- 1 root root  21 feb 4 2017 mysqld_safe_syslog.cnf
-rw-r--r-- 1 root root 3148 oct 6 23:34 mysqld.cnf
root@mylnx12:/etc/mysql/mysql.conf.d# cat mysqld.cnf
#
# the mysql database server configuration file.
#
# you can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
# 
# one can use all long options that the program supports.
# run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# for explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
 
# this will be passed to all mysql clients
# it has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# remember to edit /etc/mysql/debian.cnf when changing the socket location.
 
# here is entries for some specific programs
# the following values assume you have at least 32m ram
 
[mysqld_safe]
socket     = /var/run/mysqld/mysqld.sock
nice      = 0
 
[mysqld]
#
# * basic settings
#
user      = mysql
pid-file    = /var/run/mysqld/mysqld.pid
socket     = /var/run/mysqld/mysqld.sock
port      = 3306
basedir     = /usr
datadir     = /var/lib/mysql
tmpdir     = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
log_bin    = mylnx12_bin
server_id   = 0
character-set-server=utf8mb4
collation-server=utf8mb4_general_ci
 
#
# instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address      = 10.21.6.7
#
# * fine tuning
#
key_buffer_size     = 16m
max_allowed_packet   = 100m
thread_stack      = 192k
thread_cache_size    = 8
# this replaces the startup script and checks myisam tables if needed
# the first time they are touched
myisam-recover-options = backup
#max_connections    = 100
#table_cache      = 64
#thread_concurrency   = 10
#
# * query cache configuration
#
query_cache_limit    = 1m
query_cache_size    = 16m
#
# * logging and replication
#
# both location gets rotated by the cronjob.
# be aware that this log type is a performance killer.
# as of 5.1 you can enable the log at runtime!
#general_log_file    = /var/log/mysql/mysql.log
#general_log       = 1
#
# error log - should be very few entries.
#
log_error = /var/log/mysql/error.log
#
# here you can see queries with especially long duration
#log_slow_queries    = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# the following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see readme.debian about
#    other settings you may need to change.
#server-id       = 1
#log_bin            = /var/log/mysql/mysql-bin.log
expire_logs_days    = 10
max_binlog_size  = 100m
#binlog_do_db      = include_database_name
#binlog_ignore_db    = include_database_name
#
# * innodb
#
# innodb is enabled by default with a 10mb datafile in /var/lib/mysql/.
# read the manual for more innodb related options. there are many!
#
# * security features
#
# read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# for generating ssl certificates i recommend the openssl gui "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
#: ssl-key=/etc/mysql/server-key.pem

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。