systemctl start mysqld 失败问题

绝地灬酷狼 2022-02-05 03:27 2107阅读 1赞

今天照着这篇文章 [《CentOS 7 下安装 MySQL 5.7》][CentOS 7 _ MySQL 5.7]在自己的 centos7 里装了 mysql 。接着照着教程，以不检查权限的方式启动 mysqld（`mysqld --user=root --skip-grant-tables &`），为 root 用户设置了初始密码。

退出 mysql 后，我通过 `kill` 强杀了 mysqld 在运行的进程（`ps -fef | grep mysqld` 获取 pid），想用 `systemctl start mysqld` 启动 mysqld，但失败。

此时 `systemctl status mysqld` 检查状态，输出如下：

root@hui:~$ systemctl status mysqld
    ● mysqld.service - MySQL Server
       Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
       Active: failed (Result: exit-code) since Sat 2019-05-04 17:06:06 CST; 6s ago
         Docs: man:mysqld(8)
               http://dev.mysql.com/doc/refman/en/using-systemd.html
      Process: 7032 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=1/FAILURE)
      Process: 7009 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
    
    May 04 17:06:03 hui systemd[1]: Starting MySQL Server...
    May 04 17:06:04 hui mysqld[7032]: Initialization of mysqld failed: 0
    May 04 17:06:04 hui systemd[1]: mysqld.service: control process exited, code=exited status=1
    May 04 17:06:06 hui systemd[1]: Stopped MySQL Server.
    May 04 17:06:06 hui systemd[1]: Unit mysqld.service entered failed state.
    May 04 17:06:06 hui systemd[1]: mysqld.service failed.

对我而言，是没有半点帮助的信息。最后在这篇文章中[《CentOS 7下MySQL服务启动失败的解决思路》][CentOS 7_MySQL] 找到解决思路。如果你不想去看，我可以在这里总结一下，就是：**请去 mysql 的日志文件寻找答案。**

首先，找到 mysqld 使用的配置文件。一般来说，在以下几个路径中：

root@hui:~$ mysql --help | grep my.cnf
                          order of preference, my.cnf, $MYSQL_TCP_PORT,
    /etc/my.cnf /etc/mysql/my.cnf /usr/etc/my.cnf ~/.my.cnf

我的配置文件是 **/etc/my.cnf** ，打开之后找 **log-error** ，其对应的路径就是错误日志所在：

log-error=/var/log/mysqld.log

然后找到了失败原因（`Could not open unix socket lock file /var/lib/mysql/mysql.sock.lock.`）：

2019-05-04T09:05:22.619471Z 0 [Note] Server hostname (bind-address): '*'; port: 3306
    2019-05-04T09:05:22.619557Z 0 [Note] IPv6 is available.
    2019-05-04T09:05:22.619575Z 0 [Note]   - '::' resolves to '::'; 
    2019-05-04T09:05:22.619646Z 0 [Note] Server socket created on IP: '::'. 
    2019-05-04T09:05:22.619705Z 0 [ERROR] Could not open unix socket lock file /var/lib/mysql/mysql.sock.lock.
    2019-05-04T09:05:22.619714Z 0 [ERROR] Unable to setup unix socket lock file. 
    2019-05-04T09:05:22.619720Z 0 [ERROR] Aborting

mysql.sock.lock 这个文件不能打开。我看了下，发现这个文件是存在的。存在也不能打开？那估计是没有权限的问题。`ll` 一下，发现这个文件是 root 用户 root 的组，现在改为 mysql 用户 mysql 组。

root@hui:~$ ll /var/lib/mysql/mysql.sock.lock                                                                                         
    -rw-------. 1 root root 5 May  4 16:46 /var/lib/mysql/mysql.sock.lock
    
    root@hui:~$ chown mysql.mysql /var/lib/mysql/mysql.sock.lock  # 修改所属

好了，大功告成!

root@hui:~$ systemctl status mysqld
    ● mysqld.service - MySQL Server
       Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
       Active: active (running) since Sat 2019-05-04 17:12:05 CST; 27min ago
         Docs: man:mysqld(8)
               http://dev.mysql.com/doc/refman/en/using-systemd.html
      Process: 7715 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
      Process: 7693 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
     Main PID: 7718 (mysqld)
       CGroup: /system.slice/mysqld.service
               └─7718 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
    
    May 04 17:12:03 hui systemd[1]: Starting MySQL Server...
    May 04 17:12:05 hui systemd[1]: Started MySQL Server.

[CentOS 7 _ MySQL 5.7]: https://blog.csdn.net/u011886447/article/details/79796802
[CentOS 7_MySQL]: https://www.cnblogs.com/ivictor/p/5146247.html