apt #2016-2018 libapt-pkg5.0 #2016-2018 ubuntu-keyring #20162018
https://www.ubuntuupdates.org/ #有两个包 apt libapt-pkg5.0
https://www.ubuntuupdates.org/package/core/bionic/main/base/libapt-pkg5.0 #第三个包 ubuntu-keyring
执行完毕即可使用apt apt-get
dpkg -i ubuntu-keyring_2018.02.28_all.deb
dpkg -i libfs6_1.0.5-1_amd64.deb
dpkg -i apt_1.6.1_amd64.deb
原文：https://www.cnblogs.com/sxgaofeng/p/12457970.html