Starting MySQL.The server quit without updating PID file (xxxx.pid).[FAILED]

　　mysql无法正常启动，查看日志报如下异常

--07T01::.929615Z  [ERROR] Fatal error: Please read "Security" section of the manual to find out how to run mysqld as root!
--07T01::.929924Z  [ERROR] Aborting
--07T01::.929970Z  [Note] Binlog end
--07T01::.930860Z  [Note] /usr/local/mysql/bin/mysqld: Shutdown complete

　　用命令行启动mysql报：

[root@CB- mysqldata]# sudo service mysqld restart
MySQL server PID file could not be found![FAILED]
Starting MySQL..The server quit without updating PID file (/data/mysqldata//CB-62876.pid).[FAILED]

　　用root用户启动，报：

mysqld: Can't create/write to file '/tmp/ib6Wq7Cs' (Errcode: 30 - Read-only file system)

　　各种权限、启动方式都试过了，仍然如此。后来重启后边解决了。目前还不知道具体什么原因引起的。初步猜测有可能是由于selinux或者备份导致的异常，先记录于此，以便后续跟进。