How to fix dpkg: error: dpkg frontend lock was locked by another process in APT

The simplest and most reliable solution is to wait for whatever process holds the lock to complete. Ubuntu typically runs automatic updates in the background.

Run this command to check if there are any apt/dpkg processes still running:

ps aux | grep -i apt
ps aux | grep -i dpkg

If you see processes listed, wait 10-15 minutes for them to complete. Check again with the same commands until they're gone, then try your apt command again.

If waiting doesn't work or you want to see exactly what's holding the lock, use the lsof command to identify the process ID:

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) of any process currently holding each lock file. Note these PIDs for the next step.

If you've confirmed a process is stuck and won't finish, use the fuser command to safely terminate it:

sudo fuser -vki -TERM /var/lib/dpkg/lock /var/lib/dpkg/lock-frontend /var/lib/apt/lists/lock

This command will prompt you to confirm termination. The -TERM flag sends a graceful termination signal (safer than kill -9).

After terminating any processes, reconfigure dpkg to finalize any pending operations:

sudo dpkg --configure --pending

This ensures any interrupted package configuration is completed and the database is consistent.

For better resilience in scripts or automated environments, you can tell apt to wait for the lock with a timeout:

sudo apt-get -o DPkg::Lock::Timeout=300 update
sudo apt-get -o DPkg::Lock::Timeout=300 install package-name

The timeout value is in seconds (300 = 5 minutes). This tells apt to wait up to 5 minutes for the lock to be released before giving up, rather than failing immediately.