Previous Plesk installer call finished unsuccessfully. PUM will not perform any update operations until Plesk installation is fixed.

Symptoms

• Plesk Update Manager (PUM) exits with this error:

  # plesk sbin pum --updates-only --list
  INFO: pum is called with arguments: ['--updates-only', '--list'] 
  ERROR: Previous Plesk installer call finished unsuccessfully. PUM will not perform any update operations until Plesk installation is fixed. 
  ERROR: Exited with returncode 50.

• Starting the Plesk Installer to finish the update fails with one of these errors:

  Installing packages
  E: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 4017744 (apt-get) 
  E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it? 
  Failed to execute a package installation command.. Will retry in 60 second(s)...

  Installing packages
  E: Could not get lock /var/lib/dpkg/lock. It is held by process 4017756 (dpkg)

Cause

The system package manager, which Plesk uses to install updates, is stuck and won't let the update start.

Resolution

Terminate all the stuck system package manager processes to be able to start the Plesk installer.

1. Kill all stuck apt and dpkg processes using their PIDs

   # kill -9 $(pgrep -f 'apt|dpkg')

2. Reconfigure broken packages

   # dpkg --configure -a

3. Update Plesk

   # plesk installer update

4. Install system updates using PUM

   # plesk sbin pum --update