There is no information in your dpkg log about why this package is installed. This package is only for UEFI systems, and the error message shows that your system is not booted in UEFI mode. Why are you installing the shim package?
** Changed in: shim-signed (Ubuntu) Status: Confirmed => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1573861 Title: package shim-signed 1.12+0.8-0ubuntu2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/shim-signed/+bug/1573861/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs