-U参数反安装包, -F参数在已经安装以前版本的包的前提下升级包软件. Both will upgrade the mypkg package if it is already installed, but if the mypkg package is not installed, the -U version will install it, whereas the -F version will not. 在已经安装包的话都会更新包, 但是如果包未安装, -U将安装而-F则不会. -U参数将反安装包, 而-F参数进行安装测试, 报告安装错误而不实际安装.