参数的更改：
skip-locking 在5.5里已经不识别了，改成skip-external-locking
basedir = /usr/local/mysql5.5
datadir =/usr/local/mysql5.5/data
innodb_data_home_dir = /usr/local/mysql5.5/data
innodb_log_group_home_dir = /usr/local/mysql5.5/data
user = mysql
innodb_read_io_threads = 8
innodb_write_io_threads = 8
innodb_io_capacity = 2000
innodb_file_format = Barracuda
第一步：
/usr/local/mysql5.5/bin/mysqld --defaults-file=/etc/my.cnf --skip-grant-tables &
第三步：
/usr/local/mysql5.5/bin/mysqladmin -uroot -p123456 shutdown
第四步：
/usr/local/mysql5.5/bin/mysqld_safe --defaults-file=/etc/my.cnf --user=mysql &
mysql> select version();
+------------+
| version() |
+------------+
| 5.5.19-log |
+------------+
1 row in set (0.00 sec)
mysql> select @@innodb_version;
+------------------+
| @@innodb_version |
+------------------+
| 1.1.8 |
+------------------+
1 row in set (0.00 sec)
至此，升级过程完毕。