ubuntu apt: how to fix this error? ... "Unable to open temporary cache: Unable to open temporar-CodePudding

I recently reinstalled ubuntu 20.04.3, and after doing some setup, I now am always getting the following error when running apt update. I must have accidentally deleted some sort of cache file or directory, but I can't figure out how to diagnose or fix this.

Can anyone suggest a way to diagnose this error and correct it? Thank you very much!

# apt update
Hit:1 http://us.archive.ubuntu.com/ubuntu focal InRelease
Hit:2 http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:3 http://us.archive.ubuntu.com/ubuntu focal-updates InRelease
Get:4 http://us.archive.ubuntu.com/ubuntu focal-backports InRelease [101 kB]
Fetched 101 kB in 1s (170 kB/s)   

** (appstreamcli:27732): CRITICAL **: 11:23:58.567: Unable to open temporary cache: Unable to open temporary cache file: No such file or directory

CodePudding user response：

Never mind! :)

I had the TMP environment variable set to /opt/tmp, but that directory had gotten deleted. After recreating that directory, all is working.

All's well that ends well.

Excelsior!