I got this error today and immediately assumed the recent dpkg update had somehow messed up apt. Fortunately, a web search showed how to fix the problem.
It would help if the error message itself mentioned the setting that needs to be increased, like this: E: Apt::Cache-Limit is too small. See apt.conf(5) for details. Then explain in the manual page what this setting actually does and how to choose good values for it. The current text is: APT uses a fixed size memory mapped cache file to store the 'available' information. This sets the size of that cache. This sounds like Cache-Limit controls the size of a file and too large values waste disk space. Is that correct? Either way, clarifications would help. It would be even better to get rid of the setting entirely, but I don't know how difficult that would be to implement.
