原因是安装oracle的时候，忘记去执行 一个root.sh文件了，当然了，需要用root用户执行：
解决办法：
[root@localhost 10.2.0]#cd /oracle/product/10.2.0/db_1

[root@localhost 10.2.0]# ./root.sh

The following environment variables are set as:
ORACLE_OWNER= oracle
ORACLE_HOME= /opt/oracle/product/10g

Enter the full pathname of the local bin directory: [/usr/local/bin]:
Copying dbhome to /oracle/product/10.2.0/db_1/bin

./root.sh: line 155: [: too many arguments
./root.sh: line 175: [: too many arguments
Copying dbhome to Copying dbhome to /oracle/product/10.2.0/db_1/bin ...
./root.sh: line 175: [: too many arguments
Copying oraenv to Copying dbhome to /oracle/product/10.2.0/db_1/bin ...
./root.sh: line 175: [: too many arguments
Copying coraenv to Copying dbhome to /oracle/product/10.2.0/db_1/bin ...

Creating /etc/oratab file... Entries will be added to the /etc/oratab file as needed by Database Configuration Assistant when a database is created Finished running generic part of root.sh script. Now product-specific root actions will be performed.