apt严重问题..安装提示nokey?不会吧

zippo_qq

我在root用户下安装的呀

提示这样
warning: apt-0.5.15cnc6-1.1.fc3.fr.src.rpm: V3 DSA signature: NOKEY, key ID e42d547b
   1:apt                    warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
########################################### [100%]
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
warning: user machbuild does not exist - using root
warning: group machbuild does not exist - using root
请问如何解决...在线等