Several solutions for mysql startup error The server quit without updating PID file

1. Directory permission problem
Authorize the mysql installation directory and data directory respectively
#chown -R mysql.mysql /usr/local/mysql
#chown -R mysql.mysql /data/mysql
#service mysqld start

2. There may already be a mysql process in the process.
Solution: use the command "ps -ef|grep mysqld" to check whether there is a mysqld process, if there is, use "kill -9 process number" to kill, and then restartmysqld!

3. It may be the second time to install mysql on the machine, and there is residual data that affects the startup of the service.
Solution: Go to the data directory /data of mysql to see if there is mysql-bin.index, delete it as soon as possible, it is the culprit.

4.mysql uses the /etc/my.cnf configuration file when no configuration file is specified at startup. Please open this file to see if the data directory (datadir) is specified under the [mysqld] section.
Workaround: Please set this line under [mysqld]: datadir = /usr/local/mysql/data

5. It may be that the /usr/local/mysql/data/mysql.pid file does not have permission to write
Solution: give permission, execute "chown -R mysql:mysql /var/data" "chmod -R755 /usr/local/mysql/data" and restart mysqld!

6.selinux is the fault, if it is a centos system, selinux will be enabled by default
Solution: close it, open /etc/selinux/config, change SELINUX=enforcing to SELINUX=disabled, save and exit and restart the machinetry

7. Delete the "ib_*" files in the mysql library file /data/mysql/, note: **Be sure to back up the database before performing this operation, because ibdata1 stores all data files, if you delete it accidentallyIf you leave the library, it will be miserable!!!(The legend goes from deleting the library to running away...), then restart mysql.

8. Checking the log shows the following error message: Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
Solution:
[[email protected] mysql]# rm -rf ib_logfile*
Then start mysql, the problem is solved!

9. Look at the log with the words "initialize buffer pool, size=128.0M", "cannot allocate memory for the pool", which probably means that enough memory cannot be allocated for the pool to use.At this time, I thought that there are related configurations in the mysql configuration file, so I changed the following parameters:
innodb_buffer_pool_size = 128
#The value in the configuration file defaults to 128M
Reduce this value and start the mysql service again, the problemsolve!

10. The mysql dependency file is missing on the system
#yum -y install libaio
#yum -y install numactl
Restart the mysql service, the problem is solved

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