Probably most of MySQL users sometimes had a situation when they would do changes in MySQL config file without restarting the server (maybe matching SET GLOBAL command to do it in run time). This could be because it is misspelled or because the given version does not support such option, the server when would refuse to start, either on operating system restart or recovering from MySQL Server crash. In any case, it is quite nasty.
Check MySQL Config files
Unlike Apache MySQL service control script does not have “configtest” option so there is no straight way to check MySQL config file for errors. However, you can do it by running mysqld –help option:
[root@sl1 tmp]# /usr/libexec/mysqld --help
080212 12:39:30 [ERROR] /usr/libexec/mysqld: unknown variable 'myis_test=1'
This does not do complete check, i.e. it is possible to allocate 80GB to buffer pool instead of 8G you intended, but at least it checks options for names which is good sanity check.
I would encourage you to run such check after you made changes to your config file for sanity purposes.