问题：
[root@localhost mysql]# ./scripts/mysql_install_db --user=mysql --basedir=/u01/app/mysql --datadir=/u01/app/mysql/data
Installing MySQL system tables...2016-01-25 15:34:36 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2016-01-25 15:34:36 0 [Note] /u01/app/mysql/bin/mysqld (mysqld 5.6.28) starting as process 10302 ...
2016-01-25 15:34:36 10302 [Note] InnoDB: Using atomics to ref count buffer pool pages
2016-01-25 15:34:36 10302 [Note] InnoDB: The InnoDB memory heap is disabled
2016-01-25 15:34:36 10302 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2016-01-25 15:34:36 10302 [Note] InnoDB: Memory barrier is not used
2016-01-25 15:34:36 10302 [Note] InnoDB: Compressed tables use zlib 1.2.3
2016-01-25 15:34:36 10302 [Note] InnoDB: Using CPU crc32 instructions
2016-01-25 15:34:36 10302 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2016-01-25 15:34:36 10302 [Note] InnoDB: Completed initialization of buffer pool
2016-01-25 15:34:36 10302 [ERROR] InnoDB: ./ibdata1 can't be opened in read-write mode
2016-01-25 15:34:36 10302 [ERROR] InnoDB: The system tablespace must be writable!
2016-01-25 15:34:36 10302 [ERROR] Plugin 'InnoDB' init function returned error.
2016-01-25 15:34:36 10302 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2016-01-25 15:34:36 10302 [ERROR] Unknown/unsupported storage engine: InnoDB
2016-01-25 15:34:36 10302 [ERROR] Aborting
2016-01-25 15:34:36 10302 [Note] Binlog end
2016-01-25 15:34:36 10302 [Note] /u01/app/mysql/bin/mysqld: Shutdown complete

原因：之前执行过一次./scripts/mysql_install_db --user=mysql --basedir=/u01/app/mysql --datadir=/u01/app/mysql/data，报错了，改完参数后，重新执行，又报了此错误

解决：
[root@localhost mysql]# pwd
/u01/app/mysql
[root@localhost mysql]# cd data
[root@localhost data]# ls
ibdata1  ib_logfile0  ib_logfile1  mysql  test
[root@localhost data]# rm -rf *
[root@localhost data]# cd ..
[root@localhost mysql]# ./scripts/mysql_install_db --user=mysql --basedir=/u01/app/mysql --datadir=/u01/app/mysql/data
日志显示成功！