MySQL startup error: several solutions to the server quit without updating PID file

1. Directory permission problem
Yes mysql The installation directory and data directory of are authorized respectively
#chown -R mysql.mysql /usr/local/mysql
#chown -R mysql.mysql /data/mysql
#service mysqld start

2. Maybe it's already in the process mysql process
resolvent ： Command “ps -ef|grep mysqld” Check to see if there is mysqld process , If used “kill -9 Process number ” Kill , And then restart it mysqld！

3. It may be the second time to install... On the machine mysql, There is residual data that affects service startup .
resolvent ： Go to mysql Data directory for /data have a look , If there is mysql-bin.index, Just delete it , It's the culprit .

4.mysql It is used when no configuration file is specified at startup /etc/my.cnf The configuration file , Please open this file to view in [mysqld] There is no specified data directory under section (datadir).
resolvent ： Please be there. [mysqld] Next set this line ：datadir = /usr/local/mysql/data

5. May be /usr/local/mysql/data/mysql.pid The file does not have permission to write
resolvent ： Give authority , perform “chown -R mysql:mysql /var/data” “chmod -R 755 /usr/local/mysql/data” And then restart it mysqld！

6.selinux To blame , If it is centos System , On by default selinux
resolvent ： Close it , open /etc/selinux/config, hold SELINUX=enforcing Change it to SELINUX=disabled After saving the disk, exit and restart the machine

7. Delete mysql The library files /data/mysql/ Medium “ib_*” file , Be careful ：** Be sure to back up the database before performing this operation , because ibdata1 All data files are stored , If you accidentally delete the Library , That would be tragic ！！！（ From deleting the library to running away ...）, And then restart mysql.

8. Check the log and there are the following error prompts ：Plugin ‘InnoDB’ registration as a STORAGE ENGINE failed.
terms of settlement ：
[[email protected] mysql]# rm -rf ib_logfile*
Then start mysql, Problem solving ！

9. Look at the words in the log “initialize buffer pool,size=128.0M”,“cannot allocate memory for the pool”, Can't allocate enough memory for pool Use . Now I think of it mysql There are relevant configurations in the configuration file , Then change the following parameters ：
innodb_buffer_pool_size = 128
# The default value in the configuration file is 128M
Turn this value down , Start again mysql service , Problem solving ！

10. Missing on system mysql The dependent files of
#yum -y install libaio
#yum -y install numactl
Restart mysql service , Problem solving