求助，关于cron、脚本的执行

[ilu]

在ubuntu中写脚本时，其中的有些语句要有root权限才能执行，比如：＂hddtemp ／dev／sda＂。那么在以普通用户登陆的时候怎样才能保证脚本顺利执行呢？不可能每次执行都要输入一次密码吧。尤其是一些计划任务，如cron中的命令。
以下是我写的一个小脚本，但是每次无法执行＂hddtemp ／dev／sda＂，见输出文件。
脚本(hdtemp):
echo +++++++++++++++++++++++++++++++++++++++++
echo ---------current time--------------------
date
echo ----------hard drive temperature---------
hddtemp /dev/sda
echo +++++++++++++++++++++++++++++++++++++++++

cron:
# m h dom mon dow command
*/5 * * * * /home/yanxu/hdtemp >> /home/yanxu/hdtemplog

输出(hdtemplog):
yanxu@yanxu-laptop:~$ cat hdtemplog
+++++++++++++++++++++++++++++++++++++++++
---------current time--------------------
Fri Aug 28 20:35:01 CST 2009
----------hard drive temperature---------
+++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++
---------current time--------------------
Fri Aug 28 20:40:02 CST 2009
----------hard drive temperature---------
+++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++
---------current time--------------------
Fri Aug 28 20:45:01 CST 2009
----------hard drive temperature---------
+++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++
---------current time--------------------
Fri Aug 28 20:50:01 CST 2009
----------hard drive temperature---------
+++++++++++++++++++++++++++++++++++++++++