How to fix dpkg: error processing triggers for man-db (--configure) in APT

Start by attempting to configure all packages that are unpacked but not yet configured. This resolves the majority of dpkg trigger errors:

sudo dpkg --configure -a

This command tells dpkg to finalize the configuration of all partially-installed packages. Wait for it to complete - if it processes man-db successfully, the issue is resolved.

If the above didn't work, try processing only the pending triggers without configuring packages:

sudo dpkg --triggers-only --pending

This focuses specifically on trigger processing and may help if the issue is isolated to trigger execution.

The debconf cache directory may be missing or corrupted. Create or verify it exists:

sudo mkdir -p /var/cache/debconf

Then try reconfiguring again:

sudo dpkg --configure -a

If dpkg appears stuck or frozen, another process might be holding a lock. Check for running dpkg processes:

ps aux | grep dpkg

If you see a stuck dpkg process, you can kill it:

sudo kill -9 <PID>

Then try reconfiguring again:

sudo dpkg --configure -a

If the issue persists and you need to unblock package installation, you can temporarily disable the man-db automatic update trigger:

echo "set man-db/auto-update false" | sudo debconf-communicate
sudo dpkg --configure -a

After package operations complete, you can re-enable it and manually update the database:

echo "set man-db/auto-update true" | sudo debconf-communicate
sudo dpkg-reconfigure man-db

If none of the above work, the last resort is to remove and reinstall man-db:

sudo apt-get remove --purge man-db
sudo apt-get clean
sudo apt-get update
sudo apt-get install man-db

This removes the problematic package entirely, clears the cache, refreshes package lists, and reinstalls a fresh copy with proper triggers.