E:can not open /var/lib/apt/lists/*** ... E:The package lists or status file could not be parsed or opened

Question

I ran sudo apt update and and so on in the terminal, and then I got this error. I can't copy and paste this error code, so I wonder what could be the problem. Is it some permissions issue or something else?

An error occurred, please run Package Manager from the right-click menu   
or apt-get in a terminal to see what is wrong  

Error message:

Error: Opening the cache (E:can not open /var/lib/apt/lists/download.docker.com linux_ubuntu_dists_focal InRelease  
- fopen (13: Permission denied), 
E:The package lists or status file could not be parsed or opened. 
This usually means that your installed packages have unmet dependencies.

Answer 1

I found an old answer from some old posts just run these commands:

sudo rm /var/lib/apt/lists/* -vf

sudo apt-get clean

sudo apt-get update

sudo apt-get upgrade

It worked for me!

Answer 2

The issue in my case was that (for some reason) the permissions for the specific file in the error message were set to 600 and the owner was _apt:root

I changed this to 644 root:root which matched the rest of the files in that directory and it worked. (Using the question filename) what I did was:

sudo chown root:root /var/lib/apt/lists//var/lib/apt/lists/download.docker.com_linux_ubuntu_dists_focal_InRelease
sudo chmod 644 /var/lib/apt/lists//var/lib/apt/lists/download.docker.com_linux_ubuntu_dists_focal_InRelease

I am not sure if it is more correct to have kept the owner to _apt but I imagine this is happening because I usually run the update command from the terminal as root rather than allow the software updater to run it so this may have affected the permissions.