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Fixing a Broken apt Lock After an Interrupted Upgrade or Installation

ByPieter Bakker

Sometimes package management on Ubuntu or Debian gets stuck because apt or dpkg can’t acquire a lock. This usually happens if an upgrade, install, or update process was interrupted or if another process is still running in the background. The error looks like this:

E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable)
E: Unable to lock directory /var/lib/apt/lists/

Here’s a short guide on how to safely resolve the problem.

Step 1 – Check which process is holding the lock

Use lsof to see what’s holding the lock file:

sudo lsof /var/lib/apt/lists/lock

If you see an apt or dpkg process that shouldn’t be running, kill it:

sudo kill <PID>

You can also double-check with:

ps aux | grep -E 'apt|dpkg'

Step 2 – Remove stale lock files

Once you’re sure no apt/dpkg processes are running, remove the lock files:

sudo rm /var/lib/apt/lists/lock
sudo rm /var/cache/apt/archives/lock
sudo rm /var/lib/dpkg/lock-frontend

Step 3 – Reconfigure dpkg and fix broken packages

Clean up any half-installed packages:

sudo dpkg --configure -a
sudo apt install -f

Step 4 – Update and upgrade

Now you should be able to refresh the package lists and upgrade safely:

sudo apt update
sudo apt upgrade
sudo apt dist-upgrade

Step 5 – Clean up unused packages

Finish with a cleanup:

sudo apt autoremove -y
sudo apt autoclean

Conclusion

A stuck apt lock can look serious, but it’s usually easy to fix. The key is to identify and stop any running processes, remove stale lock files, and then repair the package database. With these steps, you can get your package manager back into a healthy state and continue upgrading or installing software without issues.

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