mysql突然无法启动了，报错：
job for mysqld.service failed because the control process exited with error code. see "systemctl status mysqld.service" and "journalctl -xe" for details.
根据提示信息查看
systemctl status mysqld.service
‚ó mysqld.service - mysql server
loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
active: failed (result: exit-code) since thu 2019-11-21 13:08:39 cst; 16s ago
docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
process: 2592 execstart=/usr/sbin/mysqld $mysqld_opts (code=exited, status=1/failure)
process: 2560 execstartpre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/success)
main pid: 2592 (code=exited, status=1/failure)
status: "server startup in progress"
error: 13 (permission denied)
nov 21 13:08:38 vm_0_16_centos systemd[1]: starting mysql server...
nov 21 13:08:39 vm_0_16_centos systemd[1]: mysqld.service: main process exited, code=exited, status=1/failure
nov 21 13:08:39 vm_0_16_centos systemd[1]: failed to start mysql server.
nov 21 13:08:39 vm_0_16_centos systemd[1]: unit mysqld.service entered failed state.
nov 21 13:08:39 vm_0_16_centos systemd[1]: mysqld.service failed.
这里我看到了关键信息error: 13 (permission denied)，无权限？继续查看一下mysqld日志，因为不记得日志路径，所以确定一下：
$ find / -name mysqld.log /var/log/mysqld.log
查看日志：cat /var/log/mysqld.log
mysqld: file './binlog.index' not found (os errno 13 - permission denied) 2019-11-21t05:08:32.749994z 0 [warning] [my-011068] [server] the syntax 'expire-logs-days' is deprecated and will be removed in a future release. please use binlog_expire_logs_seconds instead. 2019-11-21t05:08:32.751186z 0 [system] [my-010116] [server] /usr/sbin/mysqld (mysqld 8.0.17) starting as process 2528 2019-11-21t05:08:32.753249z 0 [error] [my-010119] [server] aborting 2019-11-21t05:08:32.753432z 0 [system] [my-010910] [server] /usr/sbin/mysqld: shutdown complete (mysqld 8.0.17) mysql community server - gpl.
在这里，我得到了更为具体的信息，mysqld: file './binlog.index' not found (os errno 13 - permission denied)，好吧，先追过去看一下这个binlog。那么它的路径在哪呢？可以在etc/my.cnf配置文件中的datadir=中得到：
[root@ves mysql]# ls -l total 1852876 -rw-r----- 1 mysql mysql 56 nov 28 2018 auto.cnf -rw-r----- 1 mysql mysql 1073743056 nov 16 12:01 binlog.000704 -rw-r----- 1 mysql mysql 632852623 nov 21 12:12 binlog.000705 -rw-r----- 1 mysql mysql 178 nov 21 12:15 binlog.000706 -rw-r----- 1 root root 2844 nov 21 13:01 binlog.000707 -rw-r----- 1 root root 199 nov 21 13:01 binlog.000708 -rw-r----- 1 root root 178 nov 21 13:01 binlog.000709 -rw-r----- 1 root root 96 nov 21 13:01 binlog.index -rw------- 1 mysql mysql 1680 nov 28 2018 file11 -rw-r--r-- 1 mysql mysql 1112 nov 28 2018 came
结果很明显了，用户权限不一样，我们的mysqld用户组是mysql那么重新授权一下：
$ chgrp -r mysql /usr/local/mysql/data && chown -r mysql /usr/local/mysql/data
这时候再重启
[root@ves mysql]# service mysqld restart redirecting to /bin/systemctl restart mysqld.service
解决。
