您好，我最近将操作系统从 Ubuntu18.04 升级到 Ubuntu20.04。现在我注意到，当我这样做时sudo apt-get upgrade，我会保留包裹：
The following packages have been kept back:
build-essential cpp g++ gcc gfortran liblapack-dev liblapack3
0 upgraded, 0 newly installed, 0 to remove and 7 not upgraded.
我尝试了这里提到的方法。为了解决这个问题我尝试过
sudo apt-get dist-upgrade
但输出和以前一样。
我还尝试了 sudo aptitude full-upgrade ，解决方案也是将软件包保持在当前版本。输出如下：
The following NEW packages will be installed:
cpp-9{ab} g++-9{ab} gcc-9{ab} gfortran-9{ab} libasan5{ab} libgcc-9-dev{ab} libgfortran-9-dev{ab} libgfortran5{ab} libstdc++-9-dev{ab}
libubsan1{ab}
The following packages will be upgraded:
build-essential cpp g++ gcc gfortran liblapack-dev liblapack3
7 packages upgraded, 10 newly …