开启公测版通道：

sudo softwareupdate --set-catalog https://swscan.apple.com/content/catalogs/others/index-10.10beta-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz

开启开发版通道：

sudo softwareupdate --set-catalog https://swscan.apple.com/content/catalogs/others/index-10.10seed-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz

关闭方式：

sudo softwareupdate --clear-catalog