(/boot/efi not mounted) package shim-signed 1.23+0.9+1474479173.6c180c6-0ubuntu1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Kethen]

during 16.10 to 17.04 update, this popped up
GRUB is not maintained by Ubuntu on this computer

ProblemType: Package
DistroRelease: Ubuntu 17.04
Package: shim-signed 1.23+0.9+1474479173.6c180c6-0ubuntu1
ProcVersionSignature: Ubuntu 4.8.0-39.42-generic 4.8.17
Uname: Linux 4.8.0-39-generic x86_64
NonfreeKernelModules: wl nvidia_modeset nvidia
ApportVersion: 2.20.4-0ubuntu2
Architecture: amd64
BootEFIContents:
 fw
 fwupx64.efi
Date: Mon Mar 6 08:34:18 2017
DuplicateSignature:
 package:shim-signed:1.23+0.9+1474479173.6c180c6-0ubuntu1
 Installing for x86_64-efi platform.
 grub-install: error: cannot find EFI directory.
 dpkg: error processing package shim-signed (--configure):
  subprocess installed post-installation script returned error exit status 1
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2016-12-02 (93 days ago)
InstallationMedia: Ubuntu-GNOME 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160720)
RelatedPackageVersions:
 dpkg 1.18.10ubuntu1
 apt 1.4~rc2
SourcePackage: shim-signed
Title: package shim-signed 1.23+0.9+1474479173.6c180c6-0ubuntu1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: Upgraded to zesty on 2017-03-06 (0 days ago)

[Steve Langasek (vorlon)]

Why is /boot/efi not mounted on your system?

[Kethen (scootalootf2)]

The installation was migrated from an old system. The current host has fedora installed first so grub is maintained by it instead. Hence mounting /boit/efi doesn't seems necessary.

[Steve Langasek (vorlon)]

> The current host has fedora installed first so grub is
> maintained by it instead. Hence mounting /boot/efi doesn't
> seems necessary.

If you are running in a secureboot environment with standard Microsoft keys in firmware, you will not be able to boot the Ubuntu kernel from Fedora's GRUB; you need to use Ubuntu's shim and GRUB for this (technically only Ubuntu's shim, but you need a GRUB to go with it and it might as well be the Ubuntu GRUB). This is one reason why dual booting on UEFI systems is typically handled in the UEFI menu itself rather than in the GRUB menu.

If you don't want to use Ubuntu's grub, you /can/ uninstall the shim, shim-signed, and grub-efi-amd64'*' packages, and then you don't need to mount /boot/efi during upgrades.

In any case, it sounds like this was a local configuration error (removing /boot/efi from /etc/fstab), so closing this bug report as invalid. Thanks!