zoukankan      html  css  js  c++  java
  • How to find configuration file MySQL uses?(转)

    http://www.dbasquare.com/2012/04/01/how-to-find-mysql-configuration-file/

    A customer called me today asking for help with locating the configuration file used by one of their production MySQL instances. From the description I was given it appeared that their server had at least six different copies of my.cnf file in different locations on disk. And all were similar enough that each could actually be the one. All superfluous files were the result of a bit negligent system administration. So what turned to be the quickest and the least destructive way to find the correct one?

    Initially suspecting the server was simply running more than just one MySQL instance, I logged in to take a deeper look. But I found only one mysqld process and, indeed, several configuration files.

    All of them seemed good candidates:

    /etc/my.cnf
    /etc/mysql/my.cnf
    /var/lib/mysql/my.cnf
    ...
    

    In many cases you could simply check system process list using ps:

    server ~ # ps ax | grep '[m]ysqld'
    10801 ?        Ssl    0:27 /usr/sbin/mysqld --defaults-file=/etc/mysql/my.cnf --basedir=/usr --datadir=/var/lib/mysql --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock
    

    In many cases, because it doesn’t really have to work every time. If configuration file was not specified explicitly by an init script starting the MySQL instance, then database would used the compiled-in default and such information would not be visible in the ps output. This could happen if for example the database instance was launched “by hand” from shell. The file information would also not be visible if the process line was truncated for any.

    An alternative method could be examining information in /proc. /proc is the place where Linux kernel exposes a lot of internal information about itself, hardware and running processes through a bunch of virtual files and directories. Specifically each process has its own directory there that takes the name after the process id (or PID). Learning MySQLPID is as easy as running pidof mysqld.

    One of the files we need is called cmdline. It contains the full command that started certain process.

    server ~ # cat /proc/$(pidof mysqld)/cmdline | tr '' '
    '
    /usr/sbin/mysqld
    --defaults-file=/etc/mysql/my.cnf
    

    The configuration information is clearly visible. The tr command simply converts any characters into line breaks and is there just for readability.

    Yet another approach could be browsing the process environment information. It can also be found in /proc in a file called environ. Sometimes a startup script may leave some information there:

    server ~ # tr '' '
    ' < /proc/$(pidof mysqld)/environ | grep -i cnf
    MY_CNF=/etc/mysql/my.cnf
    

    Finally you can try figuring out the compiled-in defaults, but it won’t necessarily tell you which configuration was actually used. This method is also not 100% safe as it means attempting to start another MySQL instance, even if only to print help message, because MySQL does not seem to handle this very well and it may produce some conflicts:

    server ~ # /usr/sbin/mysqld --help --verbose --skip-networking --pid-file=$(tempfile) 2> /dev/null | grep -A1 'Default options are read'
    Default options are read from the following files in the given order:
    /etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf
    

    Specifying --pid-file here is essential as otherwise the new mysqld may overwrite the PID file of the running instance.

    All in all I was able to help my customer. But there is no foolproof way. It might happen that in certain circumstances figuring out the true my.cnf location may not be possible.

    http://www.cnblogs.com/AloneSword/p/3396140.html

  • 相关阅读:
    刷题的 vscodeleetcode
    一个简单的小程序演示Unity的三种依赖注入方式
    WCF服务端运行时架构体系详解[上篇]
    通过WCF扩展实现消息压缩
    通过“四大行为”对WCF的扩展[原理篇]
    [WCF权限控制]利用WCF自定义授权模式提供当前Principal[原理篇]
    [WCF权限控制]ASP.NET Roles授权[下篇]
    [WCF权限控制]通过扩展自行实现服务授权[提供源码下载]
    通过自定义ServiceHost实现对WCF的扩展[实例篇]
    [WCF权限控制]WCF自定义授权体系详解[实例篇]
  • 原文地址:https://www.cnblogs.com/softidea/p/5544452.html
Copyright © 2011-2022 走看看