I ran into the following error when I added a new repository to my kubuntu box and ran
E: Dynamic MMap ran out of room. Please increase the size of APT::Cache-Limit. Current value: 123123. (man 5 apt.conf)
To fix this, navigate to
/etc/apt/apt.conf.d and edit the file related to debconf which in my case was 70debconf. Add the following line to the bottom of this file and save it:
The above line sets the limit to around 200 megabytes which should be plenty. Running
sudo apt-get update once again should resolve the issue.
Hope this helps!