问题
本想设置一下mysql log 日志时间，修改了 my.inf 之后， restart mysqld 一直起不来，查看服务状态，一直是 deactivating (stop-sigterm)
# systemctl status mysqld
● mysqld.service - MySQL Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
Active: deactivating (stop-sigterm) (Result: exit-code)
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 1130 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=1/FAILURE)
Process: 1031 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
CGroup: /system.slice/mysqld.service
└─1233 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mys...
8月 17 18:27:46 centos-192 systemd[1]: Starting MySQL Server...
8月 17 18:31:04 centos-192 systemd[1]: mysqld.service: control process exit...1
Hint: Some lines were ellipsized, use -l to show in full.加上 -l
[root@centos-192 ~]# systemctl status mysqld -l
● mysqld.service - MySQL Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
Active: deactivating (stop-sigterm) (Result: exit-code)
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 1130 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=1/FAILURE)
Process: 1031 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
CGroup: /system.slice/mysqld.service
└─1233 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
8月 17 18:27:46 centos-192 systemd[1]: Starting MySQL Server...
8月 17 18:31:04 centos-192 systemd[1]: mysqld.service: control process exited, code=exited status=1
8月 18 06:28:42 centos-192 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.
8月 18 06:28:53 centos-192 mysqld[2075]: Initialization of mysqld failed: 0
8月 18 06:28:53 centos-192 systemd[1]: mysqld.service: control process exited, code=exited status=1
8月 18 06:29:10 centos-192 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.
8月 18 06:29:10 centos-192 systemd[1]: Unit mysqld.service entered failed state.
8月 18 06:29:10 centos-192 systemd[1]: mysqld.service failed.
8月 18 06:29:11 centos-192 systemd[1]: mysqld.service holdoff time over, scheduling restart.
8月 18 06:29:11 centos-192 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.
8月 18 06:29:11 centos-192 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.
8月 18 06:29:21 centos-192 mysqld[2126]: Initialization of mysqld failed: 0
8月 18 06:29:21 centos-192 systemd[1]: mysqld.service: control process exited, code=exited status=1没有看出一个所以然！
查看日志
# head /var/log/mysqld.log
2023-08-11T12:22:52.567256Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2023-08-11T12:22:55.551353Z 0 [Warning] InnoDB: New log files created, LSN=45790
2023-08-11T12:22:56.101603Z 0 [Warning] InnoDB: Creating foreign key constraint system tables.
2023-08-11T12:22:56.558025Z 0 [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: cd6d347e-3841-11ee-9af3-00155d32bd0b.
2023-08-11T12:22:56.616202Z 0 [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened.
2023-08-11T12:22:57.763072Z 0 [Warning] A deprecated TLS version TLSv1 is enabled. Please use TLSv1.2 or higher.
2023-08-11T12:22:57.763093Z 0 [Warning] A deprecated TLS version TLSv1.1 is enabled. Please use TLSv1.2 or higher.
2023-08-11T12:22:57.766023Z 0 [Warning] CA certificate ca.pem is self signed.
2023-08-11T12:22:58.002974Z 1 [Note] A temporary password is generated for root@localhost: TD%TZ*jB.7Tk
2023-08-11T12:23:28.164212Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).看到这一条： Warning TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
才想起来，原来是我设置 mysql 日志格式造成的 ？
去掉这一行设置
# vim /etc/my.cnf
# wzh 20230817
# default-time-zone='Asia/Shanghai'现在是这样子
# vim /etc/my.cnf
...
# wzh 20230817
# default-time-zone='Asia/Shanghai'
explicit_defaults_for_timestamp=true
log_timestamps=SYSTEM另外日志中出现 " ... Security ... " ，安装完 centos 7 虚拟机，一直没有关闭 Selinux ！ 手动关掉后，reboot！
总结：
突然出现奇怪问题的时候，先看服务状态，再看 log ，想象自己修改过什么配置
本次问题原因在于： default-time-zone='Asia/Shanghai'