Plesk update on Debian/Ubuntu fails: dpkg was interrupted, you must manually run 'dpkg --configure -a' to correct the problem

Symptoms

• Plesk update fails on Debian/Ubuntu-based distributions:

  # plesk installer update
  ...
  E: dpkg was interrupted, you must manually run 'dpkg --configure -a' to correct the problem.
  Plesk is down, performing full restart.
  ...
  ERROR: An error occurred on attempt to install packages.
  Attention! Your software might be inoperable.
  Please contact product technical support.
  exit status 1

• Plesk Update Manager reports the following error message:

  # plesk sbin pum --check
  INFO: pum is called with arguments: ['--check']
  E: dpkg was interrupted, you must manually run 'dpkg --configure -a' to correct the problem.
  ERROR: Exited with returncode 100.
  exit status 100

• The error below is displayed in Plesk at Tools & Settings > System Updates:

  PLESK_ERROR: The System Updates tool is already installing updates in automatic mode. Please try later.

Cause

Some packages are half-configured (tagged with F flag):

# dpkg -l | grep '^iF'
iF grub-pc 2.06-3~deb11u6 amd64 GRand Unified Bootloader, version 2 (PC/BIOS version)

This may happen of a previous update was interrupted or hung and several packages are partly installed.

Resolution

1. Connect to the server via SSH .

2. Ensure you have full server snapshots. While the following steps are generally safe, they can sometimes lead to data loss or irreversible changes in certain scenarios. Having reliable backups is highly recommended.

3. Complete the installation of half-configured packages by running:

   # dpkg --configure -a

   Note: This command may fail if dependencies or package states are severely broken. In that case, proceed to the next steps.

4. Attempt to rerun the Plesk installer, skipping the package manager check:

   # PLESK_INSTALLER_SKIP_PACKAGE_MANAGER_CHECK=1 plesk installer update --skip-cleanup

   Note: Instead of update, you may use the same command you used previously (e.g., upgrade or install).

5. If the command in the previous step ends with:

   You already have the latest version of product(s) and all the selected components installed.
   Installation will not continue.

   run:

   # plesk repair installation

6. If step 4 fails and dpkg --audit suggests certain packages need to be reinstalled, run:

   # apt-get install --reinstall <packages>

   Replace <packages> with the names of the packages flagged by dpkg --audit.

7. Finally, run the Plesk installer again to revert temporary changes and ensure the issues are resolved:

   # plesk installer update