当我登录 Ubuntu 18.04 LTS 系统时，我收到以下消息：
5 additional security updates can be applied with ESM Apps.
Learn more about enabling ESM Apps service at https://ubuntu.com/esm
我的问题是如何找出哪些软件包需要这些 ESM 更新。我认为答案是“apt update && apt Upgrade”，但这并不表明需要任何更新：
# apt update && apt upgrade
Hit:1 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:2 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Hit:3 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:5 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
Reading package lists... Done
Building dependency …