How to fix E: Dynamic MMap ran out of room. Please increase the size of APT::Cache-Start in APT

Run apt update with an increased cache limit to verify the fix works:

sudo apt-get update -o APT::Cache-Limit=100000000

This sets the cache limit to 100MB for this single command. If update succeeds, your issue is confirmed and you can proceed to permanent fix.

Edit the apt configuration file to make the cache limit increase permanent:

sudo nano /etc/apt/apt.conf.d/70debconf

Add this line at the end of the file:

APT::Cache-Limit "100000000";

Save the file (Ctrl+O, Enter, Ctrl+X) and run:

sudo apt-get update

If the file doesn't exist, create a new configuration file:

sudo nano /etc/apt/apt.conf.d/99cache-limit

Add the same line above and save.

If the above doesn't resolve the issue, increase the initial cache allocation:

sudo nano /etc/apt/apt.conf.d/70debconf

Add or modify these lines:

APT::Cache-Start "50000000";
APT::Cache-Grow "2000000";
APT::Cache-Limit "200000000";

These values allocate 50MB initially, grow by 2MB steps, and limit to 200MB maximum.

Identify if you have unnecessary repositories consuming cache space:

sudo add-apt-repository --list

Remove any duplicate mirrors or unused repositories:

sudo add-apt-repository --remove ppa:repository/name

Remove third-party PPAs you don't actively use, as they contribute significantly to the package count. Consolidate on stable official repositories when possible.