chown -- change owner
useful method:
chown root.root filename ---change the filename as root group root user .
chown bob.bob filename -- change the file as bob group bob user.
chmod --- change file pemission
the file have read write excute pemission .
use ls -l display the file pemission.
eg. chmod 777 file
chmod +x file
原文：http://www.cnblogs.com/Hackerman/p/4437015.html