Bootloader fails to install on installation on NAS (QNAP TS-451)

[nidovac]

I have an unusual problem while installing LUbuntu. I want to install it on my NAS (a QNAP TS-451). It has an internal USB pinheader where I connect a normal 128 GB USB-Stick. Fortunately the NAS has a HDMI output and plenty other USB connections so that I can connect a monitor and mouse/keyboard. The NAS as 1 GB RAM.
The BIOS is a bit limited but I can run Clonezilla to make backup and write them back…and I can run the LUbuntu live-DVD.
Therefore I tried to install LUbuntu on the NAS with the USB-Stick as bootdrive.

I selected minimal installation and connected to my WiFi, so that updates can happen during installation.
With respecto to partitioning, I seletected the GUID Partition Table and the following partitions:

• 400 MB, fat32, mountpaoint /boot/efi with boot Flag set
• 117819 MB (the rest) as ext2 and with mountpoint “/”

Installation works fine until the bootloader was to be installed. Then I get the installation failure:
"The bootloader could not be installed. The installation command

grub-install --target=x86_64-efi --efi-directory=/boot/efi
--bootloader=id=ubuntu --force

returned error code 1

I have absolutely zero knowledge about UEFI and bootloaders. I already installed LUbunto on two ‘normal’ computers without any problems and they now serve as fileserver and its backup…but does anybody have an idea what went wrong and how I could install the bootloader to load in LUbuntu? Any help would be greatly appreciated

[humpty]

Does your nas support uefi boot ?

[nidovac]

I am no expert on it…but in the BIOS you can select if the bootdevice should be booted normally or as UEFI. And indeed I can boot Clonezilla also as UEFI

[humpty]

Is there a BIOS option called Secure Boot? If so, you could try turning that off.

[eeyore]

Is /boot/efi full? If it is, you might be able to delete an old kernel if there’s more than one there…

[nidovac]

/boot/efi surely is not full…on installation I freshly re-partitioned and re-formated the USB stick…so all partitions are empty

[eeyore]

Well, I defer… If all else fails, you might try mkusb-minp

e.g.

sudo -s
./mkusb-minp -p {ubuntu-live-iso} /dev/{usb}

So, this will install a persistent system on the usb. You can boot it, update it, configure, maintain, etc. Except for the kernel.

When a new kernel is issued you can mount partition 3 of the usb and (e.g.) do an rsync backup:

rsync -axHAWXS --numeric-ids --info=progress2 {mounted partition 3}/ {backup-area}
(the slash is necessary for rsync)
unmount
./mkusb-minp -p {ubuntu-new-live-iso} /dev/{usb}
mount
rsync -axHAWXS --numeric-ids --info=progress2 {backup-area}/ {mounted partition 3}

… your state is maintained and the kernel is updated