I noticed once an error starting MySQL server:
150821 20:34:03 InnoDB: Fatal error: cannot allocate memory for the buffer pool
150821 20:34:03 [ERROR] Plugin ‘InnoDB’ init function returned error.
150821 20:34:03 [ERROR] Plugin ‘InnoDB’ registration as a STORAGE ENGINE failed.
150821 20:34:03 [ERROR] Unknown/unsupported storage engine: InnoDB
150821 20:34:03 [ERROR] Aborting
Removing the following files did not help:
sudo rm /var/lib/mysql/ib_logfile0
sudo rm /var/lib/mysql/ib_logfile1
sudo rm /var/lib/mysql/ibdata1
sudo service mysql restart
The cause of the error was a lack of RAM.
You can see the amount of free memory for example with the command:
free -m
After adding RAM (RAM) to the server, this error was no longer displayed.
See also my article:
Installing and configuring MySQL server