In a high-speed network environment, this seems to occur more frequently due to the greater number of accesses within a given time period.
The problem is the number of accesses within a certain period of time, so if an error occurs, apt upgrade again after some time, and this time the error seems to disappear.
I do the following: If apt upgrade fails, I sleep for 60 seconds and try apt upgrade again. This is repeated until it succeeds.
until (apt -y upgrade) do sleep 60; done
## Solution 3
Delete the index file.
The index file is located in /var/lib/apt/lists
Let’s delete it. Just mv it to be safe.
sudo mv /var/lib/apt/lists ~/
Again, use the apt command to update. This will be a full download, so it will take some time.