dpkg was interrupted, you must manually run 'dpkg --configure -a' to correct the problem

What the message looks like

$ sudo apt upgrade
E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem.

Common causes

• The previous apt or dpkg run was cut off: SSH session lost, reboot, power loss or a killed process.
• A package script (postinst) failed, so the package stayed in a half-configured state.
• The disk or /var ran full during the installation.
• Unattended upgrades were interrupted by a shutdown.

Check

1. Is apt or dpkg still running? If yes, wait for it.
   ps -eo pid,etime,cmd | grep -E '[a]pt|[d]pkg'Copy
2. Which packages are in a broken state?
   sudo dpkg --auditCopy
3. Is there free space?
   df -h / /var /bootCopy
4. What happened in the last run?
   tail -n 30 /var/log/dpkg.logCopy

Fix

• Make sure no apt or dpkg process is running. Never delete the lock files while one is.
• Finish the interrupted work: sudo dpkg --configure -a.
• Then repair dependencies: sudo apt --fix-broken install.
• If one package keeps failing, read its error. Free disk space first if the disk was full, then repeat the two commands.
• Last resort for one package that cannot be configured: remove it with sudo dpkg --remove --force-remove-reinstreq PACKAGE and install it again. Be careful with system packages.

FAQ

Can I just delete the lock file?

No. The message is not about a lock. Run dpkg --configure -a. Deleting locks while a process works can corrupt the package database.

Is it safe to run dpkg --configure -a on a production server?

Yes, it only finishes what was started. Check free space first, and run it in a screen or tmux session so a lost connection does not interrupt it again.