内容:
Upgrade will attempt to gently upgrade the whole system. Upgrade will never install a new package or remove an existing package, nor will it ever upgrade a package that might cause some other package to break. This can be used daily to relatively safely upgrade the system. Upgrade will list all of the packages that it could not upgrade, this usually means that they depend on new packages or conflict with some other package. dselect orapt-get install
can be used to force these packages to install.
所以,如果需要升级某个包的版本,比如装CMake3.8,gcc-8等,需要手工处理。