我正在运行 Ubuntu 20.04.2 (5.8.0-53-generic)，并安装了 R 版本 4.0.5 (2021-03-31) -- “Shake and Throw”。今天我用 更新了系统，sudo apt update突然sudo apt upgrade我的所有 R 包都消失了（只剩下基础包）。幸运的是，我有昨天的 Timeshift 快照，这样我就可以回到更新前的状态。当我现在运行时sudo apt update，apt list --upgradable我得到了这个列表：
gstreamer1.0-alsa/focal-updates,focal-security 1.16.2-4ubuntu0.1 amd64 [upgradable from: 1.16.2-4]
gstreamer1.0-gl/focal-updates,focal-security 1.16.2-4ubuntu0.1 amd64 [upgradable from: 1.16.2-4]
gstreamer1.0-plugins-base-apps/focal-updates,focal-security 1.16.2-4ubuntu0.1 amd64 [upgradable from: 1.16.2-4]
gstreamer1.0-plugins-base/focal-updates,focal-security 1.16.2-4ubuntu0.1 amd64 [upgradable from: 1.16.2-4]
gstreamer1.0-x/focal-updates,focal-security 1.16.2-4ubuntu0.1 amd64 [upgradable from: 1.16.2-4]
initramfs-tools-bin/focal-updates 0.136ubuntu6.5 amd64 [upgradable from: 0.136ubuntu6.4]
initramfs-tools-core/focal-updates,focal-updates 0.136ubuntu6.5 all [upgradable from: 0.136ubuntu6.4]
initramfs-tools/focal-updates,focal-updates 0.136ubuntu6.5 all [upgradable from: 0.136ubuntu6.4]
libgstreamer-gl1.0-0/focal-updates,focal-security 1.16.2-4ubuntu0.1 amd64 [upgradable from: 1.16.2-4]
libgstreamer-plugins-base1.0-0/focal-updates,focal-security 1.16.2-4ubuntu0.1 amd64 [upgradable from: 1.16.2-4]
liblzf1/focal-updates,focal-security 3.6-2~ubuntu1.20.04.2 amd64 [upgradable from: 3.6-2~ubuntu1.20.04.1]
libssl-dev/focal-updates 1.1.1f-1ubuntu2.4 amd64 [upgradable from: 1.1.1f-1ubuntu2.3]
libssl1.1/focal-updates 1.1.1f-1ubuntu2.4 amd64 [upgradable from: 1.1.1f-1ubuntu2.3]
openssl/focal-updates 1.1.1f-1ubuntu2.4 amd64 [upgradable from: 1.1.1f-1ubuntu2.3]
r-base-core/focal-cran40 4.1.0-1.2004.0 amd64 [upgradable from: 4.0.5-1.2004.0]
r-base-dev/focal-cran40 4.1.0-1.2004.0 all [upgradable from: 4.0.5-1.2004.0]
r-base-html/focal-cran40 4.1.0-1.2004.0 all [upgradable from: 4.0.5-1.2004.0]
r-base/focal-cran40 4.1.0-1.2004.0 all [upgradable from: 4.0.5-1.2004.0]
r-doc-html/focal-cran40 4.1.0-1.2004.0 all [upgradable from: 4.0.5-1.2004.0]
r-recommended/focal-cran40 4.1.0-1.2004.0 all [upgradable from: 4.0.5-1.2004.0]
virtualbox-dkms/focal-updates,focal-security 6.1.16-dfsg-6~ubuntu1.20.04.2 amd64 [upgradable from: 6.1.16-dfsg-6~ubuntu1.20.04.1]
virtualbox-qt/focal-updates,focal-security 6.1.16-dfsg-6~ubuntu1.20.04.2 amd64 [upgradable from: 6.1.16-dfsg-6~ubuntu1.20.04.1]
virtualbox/focal-updates,focal-security 6.1.16-dfsg-6~ubuntu1.20.04.2 amd64 [upgradable from: 6.1.16-dfsg-6~ubuntu1.20.04.1]
有没有人也遇到过这个问题？我怎样才能更新所有内容而不再次丢失 R 包？