E: Package 'package ' has no installation candidate的原因分析 /etc/apt/sources.list
Whenyoutrytoinstallapackageusingapt-get,APTsearchesit’sowndatabaseforthepackagename,ifthepackageisavailableinthedatabase,thenitlooksfortherepositoryfromwheretodownloadthepackage.Itthendownloadthepacka