How to fix E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) in APT

The most common cause is Ubuntu's automatic background update process. Try waiting 5-15 minutes for it to finish.

Check if any apt processes are running:

ps aux | grep -E 'apt|dpkg'

If you see processes like 'unattended-upgrades' or 'apt-get update', let them complete. You can also check the apt logs:

sudo tail -f /var/log/apt/history.log

Once you don't see any apt-related processes, your command should work.

If waiting doesn't work, check which process is holding the lock files:

sudo lsof /var/lib/dpkg/lock
sudo lsof /var/lib/apt/lists/lock
sudo lsof /var/cache/apt/archives/lock

This will show you the process ID (PID) holding each lock. The output shows the process name and ID. If you see a process that's stuck or no longer needed, you can proceed to the next step.

Only do this if you've confirmed a stalled process is holding the lock. Never kill a process that's actively installing critical system updates.

If the process is stuck or appears to be old (check with ps aux), terminate it:

sudo kill -9 <PID>

Replace <PID> with the actual process ID from the previous step. After killing it, retry your apt command.

Warning: If the process is actively installing packages, killing it could leave your system in a broken state. Use this only as a last resort for stuck processes.

If apt operations were interrupted, dpkg's internal state may be corrupted. Repair it with:

sudo dpkg --configure -a

This command reconfigures any partially installed packages and fixes missing dependencies. Follow any prompts on screen. After this completes, try your apt command again.

If none of the above works, a reboot will clear all locks and running processes:

sudo reboot

Wait for the system to fully restart (2-3 minutes), then try your apt command. Upon boot, if there are pending package operations, apt will resume or complete them automatically.