When performing a system update (initiated the GUI way), I got caught in an infinite loop during update of grub-pc. See details below.
The system on which the problem arises and how it was set up
My computer is a dual boot Windows 10 / Xubuntu 18.04 one. It has 7 partitions on a DOS-partitioned SSD and it uses the EFI-mechanism during boot:
NAME LABEL FSTYPE MOUNTPOINT
sda
├─sda1 System-reserviert ntfs
├─sda2 SSD-Windows-Sys ntfs
├─sda3 SSD-EFI vfat /boot/efi
├─sda4
├─sda5 SSD-Linux-Home ext4 /home
├─sda6 SSD-Windows-Home ntfs
└─sda7 SSD-Linux-Sys ext4 /
When I got the computer some years ago, it only had Windows 10 plus the system reserved partition which now has become /dev/sda1. After I had resized partitions and created a separate partition for Windows home, I installed Xubuntu 16.04 and when doing so, I created a Linux System partition, a Swap partition plus a Linux-Home partition. I discarded the Linux Swap partition when I cloned everything to the SSD which was to replace the HDD which I had before (after intemediate steps to repair the not working boot setup).
When upgrading the system to Xubuntu 18.04 I got into much trouble: I was not offered the option to install it alongside Windows. I had to use the "something else" way during installation.
The result was a computer which either did not boot at all, or it booted only to Windows or it booted only to Linux. But /dev/sda7 looked to me like a system partition.
Probably with Xubuntu 16.04 the System-reserved partition also worked as ESP although it is formatted as ntfs. Its current content (possibly including leftover from the previous dual boot installation working with Xubuntu 16.04) is like this:
$ tree -L 3 /media/verwalter/System-reserviert/
/media/v/System-reserviert/
├── Boot
│ ├── BCD
│ ├── BCD.LOG
│ ├── BCD.LOG1
│ ├── BCD.LOG2
│ ├── bg-BG
│ │ └── bootmgr.exe.mui
│ ├── BOOTSTAT.DAT
│ ├── bootuwf.dll
│ ├── bootvhd.dll
│ ├── cs-CZ
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── da-DK
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── de-DE
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── el-GR
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── en-GB
│ │ └── bootmgr.exe.mui
│ ├── en-US
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── es-ES
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── es-MX
│ │ └── bootmgr.exe.mui
│ ├── et-EE
│ │ └── bootmgr.exe.mui
│ ├── fi-FI
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── Fonts
│ │ ├── chs_boot.ttf
│ │ ├── cht_boot.ttf
│ │ ├── jpn_boot.ttf
│ │ ├── kor_boot.ttf
│ │ ├── malgun_boot.ttf
│ │ ├── malgunn_boot.ttf
│ │ ├── meiryo_boot.ttf
│ │ ├── meiryon_boot.ttf
│ │ ├── msjh_boot.ttf
│ │ ├── msjhn_boot.ttf
│ │ ├── msyh_boot.ttf
│ │ ├── msyhn_boot.ttf
│ │ ├── segmono_boot.ttf
│ │ ├── segoen_slboot.ttf
│ │ ├── segoe_slboot.ttf
│ │ └── wgl4_boot.ttf
│ ├── fr-CA
│ │ └── bootmgr.exe.mui
│ ├── fr-FR
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── hr-HR
│ │ └── bootmgr.exe.mui
│ ├── hu-HU
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── it-IT
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── ja-JP
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── ko-KR
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── lt-LT
│ │ └── bootmgr.exe.mui
│ ├── lv-LV
│ │ └── bootmgr.exe.mui
│ ├── memtest.exe
│ ├── nb-NO
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── nl-NL
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── pl-PL
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── pt-BR
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── pt-PT
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── qps-ploc
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── qps-plocm
│ │ └── bootmgr.exe.mui
│ ├── Resources
│ │ ├── bootres.dll
│ │ └── de-DE
│ ├── ro-RO
│ │ └── bootmgr.exe.mui
│ ├── ru-RU
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── sk-SK
│ │ └── bootmgr.exe.mui
│ ├── sl-SI
│ │ └── bootmgr.exe.mui
│ ├── sr-Latn-CS
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── sr-Latn-RS
│ │ └── bootmgr.exe.mui
│ ├── sv-SE
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── tr-TR
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── uk-UA
│ │ └── bootmgr.exe.mui
│ ├── zh-CN
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ ├── zh-HK
│ │ ├── bootmgr.exe.mui
│ │ └── memtest.exe.mui
│ └── zh-TW
│ ├── bootmgr.exe.mui
│ └── memtest.exe.mui
├── bootmgr
├── BOOTNXT
├── BOOTSECT.BAK
├── EFI
│ ├── Boot
│ │ ├── bkpbootx64.efi
│ │ └── bootx64.efi
│ ├── Microsoft
│ │ ├── Boot
│ │ └── Recovery
│ └── ubuntu
│ └── shimx64.efi
├── Recovery
│ └── Logs
├── $RECYCLE.BIN
│ ├── S-1-5-21-1255711166-3792583174-1275079413-1008
│ │ └── desktop.ini
│ └── S-1-5-21-1255711166-3792583174-1275079413-1009
│ └── desktop.ini
├── System Volume Information
│ ├── Chkdsk
│ │ ├── Chkdsk20190923203942.log
│ │ └── Chkdsk20190923204533.log
│ ├── IndexerVolumeGuid
│ ├── tracking.log
│ └── WPSettings.dat
├── $WINRE_BACKUP_PARTITION.MARKER
└── WinSich
└── W530
58 directories, 103 files
Most probably the installation process (ubiquity) did not recognize this as EFI System Partition (ESP) and consequently it created not proper booting installation.
Finally I manually created an ESP, formatted as VFAT. During my last install process I manually marked this partition /dev/sda3/ in the GpartEd like part as “Use as EFI System partition”. This gave it the esp flag. The boot flag is to /dev/sda1 (what’s on that has been shown above).
But despite these settings, the system did not boot properly letting me choose in Grub-menu which system to boot. The Grub-bootloader was missing in the EFI partition.
I finally got this resolved by using the ISO image installation stick from which I had installed Xubuntu 18.04 onto /dev/sda7. There I did this (following the hint from How can I reinstall GRUB to the EFI partition?):
sudo mount /dev/sda7 /mnt
sudo mount /dev/sda3 /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i;
mount
sudo chroot /mnt
grub-install /dev/sda
update-grub
exit
Finally I got a system which first shows me a Grub menu and lets me select the operating system to boot.
The Infinite Loop during System Update
I did a normal system update using the GUI way. This one included among others Linux-firmware, grub-efi-amd64.bin, grub-pc.bin. There this menu came up
dialogue devices for grub installation
When I let the mouse rest on the right sub window with the two check boxes, an explanation came up explaining that an upgrade of grub-pc was made. I should select for which devices grub-install should be done automatically. In most cases it would be reasonable to let it run automatically, so avoiding that the installed GRUB image does not fit to the Grub-modules or to grub.cfg. If I were unsure which device the BIOS uses to boot, it would be best to install GRUB in all devices. There also was a hint about the possibility to install GRUB into boot blocks of partitions. Some appropriate partitions were told to be offered here. This however would force GRUB to use a blocklist mechanism which were less reliable and therefore it was not recommended.
I in the first turn I checked both checkmarks because of my installation procedure (see above). But then I got this error message:
i-386-pc wird für Ihre Plattform installiert grub-install: Fehler: Für /, konnte kein GRUB-Laufwerk gefunden werden. Überprüfen Sie Ihre device-map.
accompanied with this dialogue telling me that Grub could not be written to the boot device and askint me wether I would continue. It was accompanied with a check box.
The help function explained that GRUB could not be installed in /. If I would continue, the computer possibly would not boot properly. Therefore I did not check the box in front of the question.
This returned me to the first dialogue asking for devices for GRUB-installation.
After I had checked both boxes last time, I first removed the checkmark from the first one. This led me again to the subsequent dialogue (see above). I did not check the checkmark in front of the question, as before which returnet me to where I always had been before.
This time I did mny choice exactly the other way around which in turn brought me to the same second dialogue (see above). So I am caught in an infinite loop unless I take the potentially harmful way out selecting none of the two offered partitions and checking the box in “Configure grub-pc”.
So, what shall I do? I don't want to get my system back to not booting at all or not letting me select which system to boot.
