今天打开站点，发现跳出错误 Error establishing a database connection。

去后台看了眼数据库，尝试重启失败。
尝试重启：systemctl start mysql

Job for mysqld.service failed because the control process exited with error code.
See "systemctl status mysqld.service" and "journalctl -xeu mysqld.service" for details.

查看状态systemctl status mysql.service

× mysqld.service - LSB: start and stop MySQL
     Loaded: loaded (/etc/init.d/mysqld; generated)
     Active: failed (Result: exit-code); 5min ago
       Docs: man:systemd-sysv-generator(8)
    Process: 4877 ExecStart=/etc/init.d/mysqld start (code=exited, status=1/FAILURE)
        CPU: 3.696s

systemd[1]: Starting LSB: start and stop MySQL...
mysqld[4877]: Starting MySQL..... * The server quit without updating PID file 
systemd[1]: mysqld.service: Control process exited, code=exited, status=1/FAILURE
systemd[1]: mysqld.service: Failed with result 'exit-code'.
systemd[1]: Failed to start LSB: start and stop MySQL.

再看启动Log：

mysqld: File './mysql-bin.000028' not found (OS errno 2 - No such file or directory)
[ERROR] [MY-010958] [Server] Could not open log file.
[ERROR] [MY-010041] [Server] Can't init tc log
[ERROR] [MY-010119] [Server] Aborting

看了眼目录下有个mysql-bin.000027，于是直接复制了一份。

cp mysql-bin.000027 mysql-bin.000028
chown mysql:mysql mysql-bin.000028

重启成功。

后续：查到了类似的问题，说是把mysql-bin.*全删了，或者把mysql-bin.index中相关的文件名删掉。但至于是怎么出现的问题，还是不清楚。