zoukankan      html  css  js  c++  java
  • CentOS 7上更改MySQL数据库存储目录浅析

     

    个人之前总结过两篇文章MySQL更改数据库数据存储目录Ubuntu上更改MySQL数据库数据存储目录,都是在工作中遇到相关案例后的一个简单总结。当初的经验不足,认知有限,所以现在来看来,当初的博文确实显得浅析和不够全面,这个也没有办法,当时有些环境或案例没有涉及过,所以文章很难面面俱到,略显单薄和浅显,这个也很正常。博客不是论文,只是个人的笔记和知识点的总结。而且是基于当时的认知的经验总结和知识概括。前阵子将监控工具DPA的数据库切换为MySQL时,又遇到了这个问题,遂总结一下。

     

    系统环境      CentOS Linux release 7.5.1804 (Core)

    MySQL版本     8.0.18 MySQL Community Server - GPL

     

     

    默认情况下,MySQL的数据目录一般位于/var/lib/mysql下

     

    1:首先,弄清楚MySQL的相关配置信息

     

        找到MySQL的数据目录,以及配置文件my.cnf、错误日志的位置。

     

    mysql> show variables like 'datadir%';
    +---------------+-----------------+
    | Variable_name | Value           |
    +---------------+-----------------+
    | datadir       | /var/lib/mysql/ |
    +---------------+-----------------+
    1 row in set (0.03 sec)
    mysql> show variables like 'log_error';
    +---------------+---------------------+
    | Variable_name | Value               |
    +---------------+---------------------+
    | log_error     | /var/log/mysqld.log |
    +---------------+---------------------+
    1 row in set (0.01 sec)
     
    mysql> 

     

     

    [root@KerryDB ~]# whereis my.cnf

    my: /etc/my.cnf

     

     

    2:对数据库做一个冷备份,以备不时之需。当然,你以可以用其它方式备份。

     

     

    [root@KerryDB ~]# service mysqld stop
    Redirecting to /bin/systemctl stop mysqld.service
     
    [root@KerryDB ~]# cp -rp /var/lib/mysql  /tmp/coldbackup

     

     

     

    3:移动数据目录到其它目录

     

    这里假设,我需要将数据库的数据目录迁移到/mysql_data/下。

     

    [root@KerryDB ~]# chown -R mysql:mysql /mysql_data/
     
    [root@KerryDB ~]# cd /var/lib
    [root@KerryDB lib]# mv mysql  /mysql_data/

     

    注意:这里建议使用mv移动数据库目录,而是不是复制(cp命令),因为执行复制时,SELinux上下文将丢失,并且您稍后必须手动进行设置,如果你使用cp命令复制文件,如果没有使用参数-p,那么要记得修改目录的属主,否则你有可能遇到MySQL error: 1017 Cant find file: (errno: 13)这样的错误

     

    mv 与cp的区别

     

    clip_image001

     

    4:修改配置文件my.cnf

     

    一般情况下,只需修改datadir和socket等参数,具体根据你实际情况来判断那些参数需要修改。

     

    #datadir=/var/lib/mysql
    #socket=/var/lib/mysql/mysql.sock
     
    datadir=/mysql_data/mysql
    socket=/mysql_data/mysql/mysql.sock

     

     

    修改过后,对于CentOS或RHEL操作系统而言,你可能需要修改SELinux的设置,而对于Ubuntu或Debian,你需要修改AppArmor的设置(这篇Ubuntu上更改MySQL数据库数据存储目已经有介绍了,这里就不重复了)。当如,对于CentOS或RHEL,如果你禁用了SELinux的话,那么就可以直接忽略这个设置,因为禁用SELinux的话,就会避免很多杂七杂八的问题,但是我们不是要回避问题,而是要弄清楚问题产生的根本原因。

     

    首先你要检查,是否开启了SELinux。如下所示:

     

    [root@KerryDB ~]# /usr/sbin/sestatus
    SELinux status:                 enabled
    SELinuxfs mount:                /sys/fs/selinux
    SELinux root directory:         /etc/selinux
    Loaded policy name:             targeted
    Current mode:                   enforcing
    Mode from config file:          enforcing
    Policy MLS status:              enabled
    Policy deny_unknown status:     allowed
    Max kernel policy version:      31
     
    [root@KerryDB ~]# getenforce
    Enforcing

     

    如果SELinux是开启状态,那么此时如果不做一些配置,那么启动MySQL服务,就会遇到类似下面这样的错误:

     

    [root@KerryDB ~]# systemctl status mysqld.service
    ● mysqld.service - MySQL Server
       Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
       Active: failed (Result: exit-code) since Mon 2020-03-09 15:43:06 +08; 2min 54s ago
         Docs: man:mysqld(8)
               http://dev.mysql.com/doc/refman/en/using-systemd.html
      Process: 14903 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS (code=exited, status=1/FAILURE)
      Process: 14879 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
     Main PID: 14903 (code=exited, status=1/FAILURE)
       Status: "Server startup in progress"
        Error: 13 (Permission denied)
     
    Mar 09 15:43:06 KerryDB systemd[1]: Starting MySQL Server...
    Mar 09 15:43:06 KerryDB systemd[1]: mysqld.service: main process exited, code=exited, status=1/FAILURE
    Mar 09 15:43:06 KerryDB systemd[1]: Failed to start MySQL Server.
    Mar 09 15:43:06 KerryDB systemd[1]: Unit mysqld.service entered failed state.
    Mar 09 15:43:06 KerryDB systemd[1]: mysqld.service failed.
     
     
     
     
    [root@KerryDB ~]# journalctl -xe
    Mar 09 15:39:05 KerryDB polkitd[731]: Registered Authentication Agent for unix-process:14836:224127979 (system bus name :1.1355 [/usr/bin/pkttyagent --notify
    Mar 09 15:39:05 KerryDB systemd[1]: Stopping MySQL Server...
    -- Subject: Unit mysqld.service has begun shutting down
    -- Defined-By: systemd
    -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
    -- 
    -- Unit mysqld.service has begun shutting down.
    Mar 09 15:39:07 KerryDB systemd[1]: Stopped MySQL Server.
    -- Subject: Unit mysqld.service has finished shutting down
    -- Defined-By: systemd
    -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
    -- 
    -- Unit mysqld.service has finished shutting down.
    Mar 09 15:39:07 KerryDB polkitd[731]: Unregistered Authentication Agent for unix-process:14836:224127979 (system bus name :1.1355, object path /org/freedeskt
    Mar 09 15:43:06 KerryDB polkitd[731]: Registered Authentication Agent for unix-process:14863:224152052 (system bus name :1.1356 [/usr/bin/pkttyagent --notify
    Mar 09 15:43:06 KerryDB systemd[1]: Starting MySQL Server...
    -- Subject: Unit mysqld.service has begun start-up
    -- Defined-By: systemd
    -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
    -- 
    -- Unit mysqld.service has begun starting up.
    Mar 09 15:43:06 KerryDB systemd[1]: mysqld.service: main process exited, code=exited, status=1/FAILURE
    Mar 09 15:43:06 KerryDB systemd[1]: Failed to start MySQL Server.
    -- Subject: Unit mysqld.service has failed
    -- Defined-By: systemd
    -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
    -- 
    -- Unit mysqld.service has failed.
    -- 
    -- The result is failed.
    Mar 09 15:43:06 KerryDB systemd[1]: Unit mysqld.service entered failed state.
    Mar 09 15:43:06 KerryDB systemd[1]: mysqld.service failed.
    Mar 09 15:43:06 KerryDB polkitd[731]: Unregistered Authentication Agent for unix-process:14863:224152052 (system bus name :1.1356, object path /org/freedeskt
    lines 4369-4401/4401 (END)

     

     

    上面日志看不到细节错误信息,此时,应该检查错误日志/var/log/mysqld.log, 如下所示,你会看到OS errno 13 - Permission deniedCan't create test file xxx"类似这样的错误

     

     

    mysqld: File './binlog.~rec~' not found (OS errno 13 - Permission denied)

    2020-03-09T07:43:06.927360Z 0 [Warning] [MY-010091] [Server] Can't create test file /mysql_data/mysql/mysqld_tmp_file_case_insensitive_test.lower-test

    2020-03-09T07:43:06.927453Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.18) starting as process 14903

    2020-03-09T07:43:06.929669Z 0 [Warning] [MY-010091] [Server] Can't create test file /mysql_data/mysql/mysqld_tmp_file_case_insensitive_test.lower-test

    2020-03-09T07:43:06.929681Z 0 [Warning] [MY-010159] [Server] Setting lower_case_table_names=2 because file system for /mysql_data/mysql/ is case insensitive

    2020-03-09T07:43:06.930542Z 0 [ERROR] [MY-010846] [Server] MYSQL_BIN_LOG::open_purge_index_file failed to open register file.

    2020-03-09T07:43:06.930594Z 0 [ERROR] [MY-010817] [Server] MYSQL_BIN_LOG::open_index_file failed to sync the index file.

    2020-03-09T07:43:06.930657Z 0 [ERROR] [MY-010119] [Server] Aborting

    2020-03-09T07:43:06.930830Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.18)  MySQL Community Server - GPL.

     

    注意:默认情况下,日志里面的时间是UTC时间,而不是本地时间。除非你设置过。具体参考我的博客MySQL5.7参数log_timestamps

     

    此时如果,你用chcon命令来在新目录中更改SELinux上下文类型,我看有些博客介绍就OK了。但是在我这个环境中,这样处理过后依然报同样的错误

     

     

    [root@KerryDB ~]# chcon -R -t mysqld_db_t /mysql_data/

    [root@KerryDB ~]#

     

    折腾测试后,发现此时需要在file_contexts里面修改mysqld_db_t,如下所示:

     

     

    [root@KerryDB ~]# cd /etc/selinux/targeted/contexts/files/

    [root@KerryDB files]# ls -lrt

     

     

    修改前:

     

    /var/lib/mysql(-files|-keyring)?(/.*)? system_u:object_r:mysqld_db_t:s0

     

    clip_image002

     

    修改后:

     

    /mysql_data/mysql(-files|-keyring)?(/.*)? system_u:object_r:mysqld_db_t:s0

     

    其实使用chcon修改对象(文件)的安全上下文,相当难掌握,有点难度,除非你是Linux高手,一般用工具semanage对默认目录的安全上下文查询与修改

     

     

    一般默认可能没有安装policycoreutils-python,需要安装对应组件

     

    #yum -y install policycoreutils-python

     

    如果你要查看MySQL相关文件的设置,那么可以用semanage fcontext -l | grep -i mysql查看。

     

    root@KerryDB ~]# semanage fcontext -l | grep -i mysql
    /usr/lib(64)?/nagios/plugins/check_mysql           regular file       system_u:object_r:nagios_services_plugin_exec_t:s0 
    /usr/lib(64)?/nagios/plugins/check_mysql_query     regular file       system_u:object_r:nagios_services_plugin_exec_t:s0 
    /etc/mysql(/.*)?                                   all files          system_u:object_r:mysqld_etc_t:s0 
    /etc/my.cnf.d(/.*)?                              all files          system_u:object_r:mysqld_etc_t:s0 
    /var/log/mysql.*                                   regular file       system_u:object_r:mysqld_log_t:s0 
    /var/lib/mysql(-files|-keyring)?(/.*)?             all files          system_u:object_r:mysqld_db_t:s0 
    /var/run/mysqld(/.*)?                              all files          system_u:object_r:mysqld_var_run_t:s0 
    /var/log/mariadb(/.*)?                             all files          system_u:object_r:mysqld_log_t:s0 
    /var/run/mariadb(/.*)?                             all files          system_u:object_r:mysqld_var_run_t:s0 
    /usr/sbin/mysqld(-max)?                            regular file       system_u:object_r:mysqld_exec_t:s0 
    /var/run/mysqld/mysqlmanager.*                     regular file       system_u:object_r:mysqlmanagerd_var_run_t:s0 
    /usr/lib/systemd/system/mysqld.*                   regular file       system_u:object_r:mysqld_unit_file_t:s0 
    /usr/share/munin/plugins/mysql_.*                  regular file       system_u:object_r:services_munin_plugin_exec_t:s0 
    /usr/lib/systemd/system/mariadb.*                  regular file       system_u:object_r:mysqld_unit_file_t:s0 
    /etc/my.cnf                                       regular file       system_u:object_r:mysqld_etc_t:s0 
    /root/.my.cnf                                    regular file       system_u:object_r:mysqld_home_t:s0 
    /usr/sbin/ndbd                                     regular file       system_u:object_r:mysqld_exec_t:s0 
    /usr/libexec/mysqld                                regular file       system_u:object_r:mysqld_exec_t:s0 
    /usr/bin/mysqld_safe                               regular file       system_u:object_r:mysqld_safe_exec_t:s0 
    /usr/bin/mysql_upgrade                             regular file       system_u:object_r:mysqld_exec_t:s0 
    /usr/sbin/mysqlmanager                             regular file       system_u:object_r:mysqlmanagerd_exec_t:s0 
    /etc/rc.d/init.d/mysqld                          regular file       system_u:object_r:mysqld_initrc_exec_t:s0 
    /var/lib/mysql/mysql.sock                         socket             system_u:object_r:mysqld_var_run_t:s0 
    /usr/bin/mysqld_safe_helper                        regular file       system_u:object_r:mysqld_exec_t:s0 
    /usr/sbin/zabbix_proxy_mysql                       regular file       system_u:object_r:zabbix_exec_t:s0 
    /etc/rc.d/init.d/mysqlmanager                    regular file       system_u:object_r:mysqlmanagerd_initrc_exec_t:s0 
    /usr/sbin/zabbix_server_mysql                      regular file       system_u:object_r:zabbix_exec_t:s0 
    /usr/libexec/mysqld_safe-scl-helper                regular file       system_u:object_r:mysqld_safe_exec_t:s0 
    /home/[^/]+/.my.cnf

     

    clip_image003

     

     

     

    [root@KerryDB  ~]# semanage fcontext -a -t mysqld_db_t "/mysql_data/mysql(/.*)?"
    [root@KerryDB  ~]# restorecon -Rv /mysql_data/mysql
    restorecon reset /mysql_data/mysql context system_u:object_r:default_t:s0->system_u:object_r:mysqld_db_t:s0

     

    此时启动MySQL实例就正常了,关于semanage修改目录或文件安全上下文的更多信息,参考资料有,可以移步那里去学习。

     

    # service mysqld start

    Redirecting to /bin/systemctl start mysqld.service

     

     

     

     

    此时,你如果用MySQL客户端工具登录数据库,就会遇到"Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock'"

     

    [root@KerryDB mysql]# mysql -u root -p
     
    Enter password: 
     
    ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

     

     

    解决下面错误的方法:

     

     

    1:在连接MySQL时,指定参数--socket的值

     

    [root@KerryDB mysql]# mysql -u root -p   --socket=/mysql_data/mysql/mysql.sock
    Enter password: 
    Welcome to the MySQL monitor.  Commands end with ; or g.
    Your MySQL connection id is 8
    Server version: 8.0.18 MySQL Community Server - GPL
     
    Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
     
    Oracle is a registered trademark of Oracle Corporation and/or its
    affiliates. Other names may be trademarks of their respective
    owners.
     
    Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
     
    mysql> 

     

    2:修改配置文件my.cnf,增加客户端参数socket

     

    [client]

    socket=/mysql_data/mysql/mysql.sock

     

    注意这个socket参数,跟mysqld下的参数socket是有所区别的。

     

    [client]
    socket=/mysql_data/mysql/mysql.sock
    [mysqld]
    datadir=/mysql_data/mysql
    socket=/mysql_data/mysql/mysql.sock

     

     

    其实这种方法是最简单,最有效的一个方法。

     

     

    3:可以通过建立mysql.sock文件的软连接

     

     

    另外,我尝试通过修改Unix-domain Socket 上下文来解决这个问题,但是没有解决,不知是我理解有误,还是其它方面原因。 下面是部分测试内容:

     

     

    # semanage fcontext -a -t mysqld_var_run_t "/mysql_data/mysql/mysql.sock"

    # restorecon -Rv /mysql_data/mysql/mysql.sock

     

    # mysql -u root -p

    Enter password:

    ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

     

    依然报错,检查semanage fcontext -l | grep -i mysql 如下所示, 由于对SELinux的知识了解不够深入,暂时还在学习中。临时先记录一下,留待以后解决。

     

    #  semanage fcontext -l | grep -i mysql

    image

     

     

     

    参考资料:

     

     

    https://dev.mysql.com/doc/refman/5.6/en/can-not-connect-to-server.html

    https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/selinux_users_and_administrators_guide/sect-security-enhanced_linux-working_with_selinux-selinux_contexts_labeling_files

     

     

     

     

     

     

     

  • 相关阅读:
    .Net在arraylist用法
    ORM查询方法
    正则表达式大全
    checkbox修改功能保存功能绑定
    Web ASP.Net运行机制
    面试题
    Sql Server 中锁的概念
    由nginx和spring boot中tomcat配置不当引起的问题
    记录一次由事务可重复读引起的问题
    Ubuntu18.04没有声音的解决
  • 原文地址:https://www.cnblogs.com/kerrycode/p/12460771.html
Copyright © 2011-2022 走看看