MySQL failed to start problem analysis and solutions

Because to debug the relationship of the program, from the background to modify the MySQL settings, set to
join_buffer_size=512k
After the result is saved MySQL cannot connect immediately, reboot Lu-restart,mysql-restart cannot connect.

Operation Successful!
Lumanager can not connect to MySQL database, please use SSH login server to check whether the MySQL database has been started
If success has started, check that the connection password is correct in the/usr/local/lumanager/conf/config.php file
If it does not start successfully, please use SSH login server, execute Mysql-restart command

Through the background to the/etc/my.cnf file changes back to the original settings, or not.
The password in the config.php is also correct.

Later check the log, found:
120215 09:59:57 mysqld_safe mysqld from PID File/home/mysql_data/localhost.localdomain.pid ended
120215 10:00:01 Mysqld_safe starting mysqld daemon with databases From/home/mysql_data
Unknown suffix ' B ' used for variable ' query_cache_size ' (value ' 0B ')
120215 10:00:01 [ERROR]/usr/local/mysql/libexec/mysqld:error while setting value ' 0B ' to ' query_cache_size '
120215 10:00:01 [ERROR] Aborting

It appears that the error was modified to 0B when the MySQL settings were modified by Query_cache_size.
And if the system requires 0KB.
However, when I modified the wood has dynamic query_cache_size parameters ah?

Other problems found on the Internet and solutions

If the MySQL datasheet uses a different account, you will also need to create an account in MySQL, or use the original MySQL datasheet to overwrite it (you need to confirm that the MSYQL datasheet was undamaged).

Resolve failed to start

Common workaround when you encounter a failure to start MySQL:

A, first use the command C:Program filesmysqlbinmysqladmin-u root-p shutdown to close MySQL

B, and then under the cmd command line, execute net start MySQL to start MySQL.

Two, 1067 error common solution
Failure phenomenon

If there is a 1067 error while stopping MySQL (net stop MySQL) or starting MySQL, the error message "MySQL service is stopping ... System error (A Systems error has occurred ...). System error 1067 has occurred., the process terminates unexpectedly (the processes terminated unexpectedly.).

Common Solutions

If you have been running OK before, please follow the "Cannot start" solution above to perform a look.
If you have a remove instance operation, after rebuilding again, be sure to check the My.ini file DataDir has been restored, if the database does not exist under the address, will also report 1067 errors, only need to modify into a real database directory address, and then manually start.
Check MySQL directory permissions
Check to see if there is a Basedir installation directory path and DATADIR database path under the [Mysqld] field in the My.ini file, My.ini may need to appear in two places, MySQL's installation directory and Windows directory (assuming it is a Windows environment), Have to check.
Sometimes delete%windir%/my.ini files and then reconfigure can also be resolved, once again configured to check the windir directory whether there are my.ini files, and sometimes the installation directory under the latest My.ini copies of the past cover can also solve the problem.
If it is a Linux environment, try to copy Mysql.server to/etc/rc.d/init.d/, then run Chkconfig mysql.server, then you can set path on the command line and use the command to perform MySQL boot.

Third, illegal shutdown caused by MySQL can not start the problem
If it is because of illegal shutdown and other reasons MySQL can not start or start a problem, it is best to use the reinstall or confirm that the MySQL data table is OK and ibdata1, Mysql.pid, IB_LOGFILE0, and other documents to cover, the days have encountered many times this situation, is the original MySQL table has a problem, always can not start, but the new table can be changed.

Four, Reload MySQL
When you find a problem with MySQL, the most convenient way is to uninstall the MySQL first, and then reinstall the reconfiguration, specific methods are as follows:
1, uninstall MySQL, clean out the installation directory and Windows directory My.ini files.
2, check the Task Manager whether there is a MySQL process, if there is, you can kill Mysqld.exe, or first kill and then uninstall can also.
3, in the cmd command window, execution: SC delete mysql, the command is the cleaning up Registration Service command.
3. Re-install MySQL

MySQL does not start properly, the 1053 wrong alternative solution

When a problem occurs, the MySQL service is registered with the Mysqld-nt install Mysqlservice, under normal circumstances, the service will start automatically when the machine restarts. However, on some (small) machines, the service does not start properly after reboot, manually start it in the service, Pop-up prompts: Error 1053 service does not respond in time to start or control requests.
At this point, if you uninstall the service at the command line using the mysqld-nt remove Mysqlservice, it prompts the uninstall to succeed, but in fact, the service still exists in the system and the service disappears after the reboot, and you can take advantage of the Mysqld-nt install Mysqlservice service, everything back to normal.