Why system updates shown by Plesk and by system package manager are different

Question

• Why are system updates shown by Plesk and by system package manager different?
• Plesk user interface excludes kernel patch updates available under Tools & Settings > System Updates;
• When Enable safe updates for system packages mode is disabled under Tools & Settings > System Updates > Settings, the kernel update patch is still not included;
• The following command shows the kernel update available:

  For CentOS/RHEL:

  # yum check-updates

  For Debian/Ubuntu:

  # apt-get -u upgrade --assume-no

Answer

Kernel updates are excluded from PUM (Plesk Update Manager) for the following reasons:

• kernel updates are handled by YUM and APT differently than other updates (i.e., the new package is usually installed instead of updating existing one, and the old package, sometimes, is removed).
• the server needs rebooting to apply the kernel updates

To install kernel updates:

1. Install kernel updates manually:

   For CentOS/RHEL:

   # yum update

   For Debian/Ubuntu:

   # apt-get update && apt-get upgrade

2. Reboot the server:

   # reboot

Alternatively, KernelCare extension can be used to make sure that a server's kernel is up-to-date. The extension allows installing kernel updates on the fly without rebooting the server.