在FreeBSD中啟動mysql時報錯，ERROR! The server quit without updating PID file，通常這是可以查看數據庫目錄下的.err日志，裡面會記錄一些具體的錯誤信息，對排錯相當有用，內容如下：
110805 17:30:19 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql5.5/data
110805 17:30:19 InnoDB: The InnoDB memory heap is disabled
110805 17:30:19 InnoDB: Mutexes and rw_locks use GCC atomic builtins
110805 17:30:19 InnoDB: Compressed tables use zlib 1.2.3
110805 17:30:19 InnoDB: Initializing buffer pool, size = 256.0M
110805 17:30:19 InnoDB: Completed initialization of buffer pool
InnoDB: Error: log file /usr/local/mysql5.5/data/ib_logfile0 is of different size 0 5242880 bytes
InnoDB: than specified in the .cnf file 0 67108864 bytes!
110805 17:30:19 [ERROR] Plugin 'InnoDB' init function returned error.
110805 17:30:19 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
110805 17:30:19 [ERROR] Unknown/unsupported storage engine: InnoDB
110805 17:30:19 [ERROR] Aborting
110805 17:30:19 [Note] /usr/local/mysql5.5/bin/mysqld: Shutdown complete
看到上面紅色字體，顯示錯誤是出在日志文件大小上，於是查看mysql的配置文件/etc/my.cnf
# Uncomment the following if you are using InnoDB tables
innodb_data_home_dir = /usr/local/mysql5.5/data
innodb_data_file_path = ibdata1:10M:autoextend
innodb_log_group_home_dir = /usr/local/mysql5.5/data
# You can set .._buffer_pool_size up to 50 – 80 %
# of RAM but beware of setting memory usage too high
innodb_buffer_pool_size = 256M
innodb_additional_mem_pool_size = 20M
# Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 64M
innodb_log_buffer_size = 8M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50
配置文件中指定瞭innodb_log_file_size=64M，在看看我的數據庫目錄下，日志文件大小是不是64M，如下圖，發現問題瞭，日志文件是5242880是5M
找到問題瞭，解決辦法可以更改配置文件，也可以刪除現在這個日志，再啟動mysql這樣它會重新生成這兩個日志文件。
怎麼會出現這個問題呢？
一般來說，是由於，在my.cnf中關於INNODB的一些配置是被註釋的，在沒有更改的情況下，系統就使用瞭默認值，這樣，當你把關於innodb的配置選項註釋去掉的時候，就會出現這個報錯！