I recently experienced this error on a DigitalOcean node with 512MB ram. The full error below:
Starting MySQL (Percona Server). ERROR! The server quit without updating PID file (/var/lib/mysql/test2.pid)
The log had the following errors logged
2015-05-25 03:46:27 3518 [Note] InnoDB: Initializing buffer pool, size = 128.0M InnoDB: mmap(137363456 bytes) failed; errno 12 2015-05-25 03:46:27 3518 [ERROR] InnoDB: Cannot allocate memory for the buffer pool 2015-05-25 03:46:27 3518 [ERROR] Plugin 'InnoDB' init function returned error. 2015-05-25 03:46:27 3518 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed. 2015-05-25 03:46:27 3518 [ERROR] Unknown/unsupported storage engine: InnoDB 2015-05-25 03:46:27 3518 [ERROR] Aborting
Turns out the VPS did not have enough RAM to allocate to the InnoDB plugin.
One fix is to disable InnoDB, because this was a test node and I really didn’t need InnoDB I was able to disable it by adding the following to my.cnf
[mysqld] innodb=OFF ignore-builtin-innodb skip-innodb default-storage-engine=myisam default-tmp-storage-engine=myisam