Apt ‘MMap ran out of room’ errors

I’m seeing this problem more and more frequently when running apt-get or apt-cache commands. It seems to get most of the way through updating itself and then dies with this error:

E: Dynamic MMap ran out of room
E: Error occured while processing rapidsvn (NewVersion1)
E: Problem with MergeList /var/state/apt/lists/something_repodata_primary.xml
E: The package lists or status file could not be parsed or opened.

My understanding is that apt is running of some cache space and quits. I think this is referring to some memory limit, but am not sure (if anybody has a better explanation of the actual problem, please comment).

The fix is easy enough. Just create a file named /etc/apt/apt.conf.d/local.conf with this line:

APT::Cache-Limit 50000000;

That raises the limit from the default (I believe 8Mb) to 50Mb and has worked well for me.