chmod用于改变文件或目录的访问权限。用户用它控制文件或目录的访问权限。该命令有两种用法。一种是包含字母和操作符表达式的文字设定法；另一种是包含数字的数字设定法。 u 表示“用户（user）”，即文件或目录的所有者。 g 表示“同组（group）用户 ...

ITworld.com – If you have tried to give away any files lately on any of your Unix systems (i.e., without first becoming root), you may have been surprised to learn that you can’t. On most Unix systems ...

copy a chmod binary from a similar system to root's home dir and run that. I think you could probably even compile it from the source (probably in http://www.gnu.org ...