Plesk updates on Debian 10 fail due to missing packages in repo: 404 Not Found

Symptoms

• Plesk updates fail on Debian 10, even though ELS license has been purchased.
• Errors that are similar to the following can be found in /var/log/plesk/install/autoinstaller3.log:

CONFIG_TEXT: Err:1 http://security.debian.org/debian-security buster/updates/main amd64 libpcre2-posix0 10.32-5+deb10u1
404 Not Found [IP: 2a01:4f8:0:1::1:97 80]

Cause

The default Debian 10 repositories that exist in /etc/apt/sources.list are deprecated, because Debian 10 reached its end of life for Long Term Support (LTS) on June 30, 2024.

Resolution

1. Connect to the server via SSH

2. Backup the sources.list file:

   # cp -a /etc/apt/sources.list /etc/apt/sources.list.bak

3. Open the /etc/apt/sources.list file with your favorite command-line text editor
4. Remove all contents

5. Add the following repositories to the file

   CONFIG_TEXT: deb http://archive.debian.org/debian buster main contrib non-free
   deb http://archive.debian.org/debian-security buster/updates main contrib non-free 

6. Save the changes and close the file
7. Update Plesk to the latest build