The dpkg package manager gets stuck in a loop while processing package triggers, usually due to corrupted state or conflicting package dependencies. This error halts system updates and package installation.
This error occurs when dpkg detects a circular dependency between package triggers and cannot resolve it. Package triggers are scripts that run after package installation or removal. When two or more packages have triggers that depend on each other without a clear resolution order, dpkg abandons the operation to prevent infinite looping. This typically happens due to corrupted package state, interrupted installations, or broken dependency chains.
First, attempt to finish any incomplete package operations that may have caused the trigger loop:
sudo dpkg --configure -aThis tells dpkg to configure all packages that are only half-installed or unpacked.
If dpkg configuration alone doesn't work, use apt to fix broken packages:
sudo apt-get install -fThe -f (--fix-broken) flag installs missing dependencies and removes conflicting packages.
If the error persists, stale lock files may be blocking resolution. Remove them:
sudo rm /var/lib/dpkg/lock-frontend
sudo rm /var/lib/dpkg/lockBe cautious only to run this when apt/dpkg is NOT running. Then retry configuration.
For persistent trigger loop issues, you may need to clear the triggers processing state:
sudo rm /var/lib/dpkg/triggers/Lock
sudo dpkg --configure --pendingThis removes the lock and reruns pending triggers configuration from scratch.
Once dpkg returns to a consistent state, verify integrity and resume system updates:
sudo apt-get update
sudo apt-get upgradeMonitor the output for any remaining errors. If they recur, note the specific package names mentioned in the error chain for further investigation.
This error was a known dpkg regression introduced in version 1.17.17 and fixed in 1.17.19. The bug was in the trigger dependency cycle detection code—dpkg wasn't smart enough to break cycles at the correct point when package A awaits triggers and package P has them pending, but both depend on each other. If you're on a very old distribution, upgrading dpkg may resolve it. In rare cases where manual fixes fail, you may need to restore /var/lib/dpkg/status from a backup (/var/lib/dpkg/status-old) and reconfigure all packages. Always create a system backup before making manual edits to dpkg state files. Some users report the issue self-resolves after restarting the installation process from scratch.
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