好久不更新的服务器今天执行命令：apt-get update 和 apt-get upgrade 都未能成功，出现如下错误：

root@iZ62g7i:~/certbot# apt-get udpate
E: Invalid operation udpate
root@iZ62g7i:~/certbot# apt-get udgrade
E: Invalid operation udgrade 

解决办法：

You have a lot of third-party repositories, and while identified as 'for Xenial', that's no guarantee that there won't be packaging conflicts at times. That said, and again from the posted images, you seem to be doing package maintenance from a graphical application. I'd suggest opening a console and doing it from the command line; it may yield more useful information, like which specific repository is being complained about.

In a console type:

sudo apt update && sudo apt full-upgrade

The first part ensures that the package information is up to date. The second part will perform an intelligent update to all existing installed packages. IF there are any issues that need attention, you will be so informed.

外国网友贴的原因和解决办法。

其实关键命令就是：

sudo apt update && sudo apt full-upgrade

输入后，系统立马更新了。