I deleted the ubuntu partition because I needed more space on the windows partition; I did this using Create and format hard disk partitions in windows - just click on start menu and type part; resizing of windows partitions should be done only from windows to avoid issues; so I resized the windows partition with a few extra GB;

luckily, I did not give all the free space that was left after deleting the ubuntu partition to windows;

so when I got the grub rescue error, upon the next reboot, the ls and set grub commands worked, but several other commands like chainloader, initrd or normal did not work; the problem was that although I did do a shutdown, windows tries to be smarter and second guess you and do a hibernate anyway, to enable a faster boot next time; so the disk was in a "dirty" inconsistent state and therefore could not be mounted, except in read-only mode which does not allow fixing anything, even using a live ubuntu usb drive, and therefore, could not fix/reinstall grub from the live ubuntu; this of course also means that windows cannot be started from grub; and naturally, the os-prober command from linux cannot find the windows system in this state either, not that it matters;

in my case, as I had free space available, I created a partition from linux, with the ubuntu live usb installer - without touching the windows partitions - and also created a new EFI partition for grub and sized it to 128MB for good measure, and installed ubuntu into the new partition using the live usb installer; it installed fine - but at the end it failed to install grub - because the windows was hibernated/dirty

so for this, I used the live ubuntu usb and installed boot-repair as follows at a terminal (ctrl+alt+t to open a terminal in ubuntu) (this is installed only in memory, not on disk, as it is a live ubuntu usb, so if you reboot, you need to redo these steps below):

sudo apt-add-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install boot-repair

then I ran boot-repair and selected the first option:

sudo boot-repair

this showed the commands to type to remove the old grub and install a new one into the EFI partition created above; then it was possible to boot in the newly installed ubuntu, using the new grub in the new EFI partition;

then in ubuntu at the terminal prompt I typed

sudo update-grub

and now the windows was also added to the grub menu and everything works again, upon the next reboot both ubuntu and windows can now be selected in the grub menu

apparently to shut down windows without the dirty hibernation, need to type at a windows command prompt

shutdown /s

If you have about 16GB of free unallocated space, or an unused partition about that size or bigger which you can format (ok to delete its contents), might work with a bit less than that size also, then this answer is for you.

I deleted the ubuntu partition because I needed more space on the windows partition; I did this using Create and format hard disk partitions in windows - just click on start menu and type part; resizing of windows partitions should be done only from windows to avoid issues; so I resized the windows partition with a few extra GB;

luckily, I did not give all the free space that was left after deleting the ubuntu partition to windows;

so when I got the grub rescue error, upon the next reboot, the ls and set grub commands worked, but several other commands like chainloader, initrd or normal did not work; the problem was that although I did do a shutdown, windows tries to be smarter and second guess you and do a hibernate anyway, to enable a faster boot next time; so the disk was in a "dirty" inconsistent state and therefore could not be mounted, except in read-only mode which does not allow fixing anything, even using a live ubuntu usb drive, and therefore, could not fix/reinstall grub from the live ubuntu; this of course also means that windows cannot be started from grub; and naturally, the os-prober command from linux cannot find the windows system in this state either, not that it matters;

in my case, as I had free space available, I created a partition from linux, with the ubuntu live usb installer - without touching the windows partitions - and also created a new EFI partition for grub and sized it to 128MB for good measure, and installed ubuntu into the new partition using the live usb installer; it installed fine - but at the end it failed to install grub - because the windows was hibernated/dirty

so for this, I used the live ubuntu usb and installed boot-repair as follows at a terminal (ctrl+alt+t to open a terminal in ubuntu) (this is installed only in memory, not on disk, as it is a live ubuntu usb, so if you reboot, you need to redo these steps below):

sudo apt-add-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install boot-repair

then I ran boot-repair and selected the first option:

sudo boot-repair

this showed the commands to type to remove the old grub and install a new one into the EFI partition created above; then it was possible to boot in the newly installed ubuntu, using the new grub in the new EFI partition;

then in ubuntu at the terminal prompt I typed

sudo update-grub

and now the windows was also added to the grub menu and everything works again, upon the next reboot both ubuntu and windows can now be selected in the grub menu

apparently to shut down windows without the dirty hibernation, need to type at a windows command prompt

shutdown /s

I deleted the ubuntu partition because I needed more space on the windows partition; I did this using Create and format hard disk partitions in windows - just click on start menu and type part; resizing of windows partitions should be done only from windows to avoid issues; so I resized the windows partition with a few extra GB;

luckily, I did not give all the free space that was left after deleting the ubuntu partition to windows;

so when I got the grub rescue error, upon the next reboot, the ls and set grub commands worked, but several other commands like chainloader, initrd or normal did not work; the problem was that although I did do a shutdown, windows tries to be smarter and second guess you and do a hibernate anyway, to enable a faster boot next time; so the disk was in a "dirty" inconsistent state and therefore could not be mounted, even using a live ubuntu usb drive, and therefore, could not fix/reinstall grub from the live ubuntu;

in my case, as I had free space available, I created a partition from linux, with the ubuntu live usb installer - without touching the windows partitions - and also created a new EFI partition for grub and sized it to 128MB for good measure, and installed ubuntu into the new partition using the live usb installer; it installed fine - but at the end it failed to install grub - because the windows was hibernated/dirty

so for this, I used the live ubuntu usb and installed boot-repair as follows (this is installed only in memory, not on disk, as it is a live ubuntu usb, so if you reboot, you need to redo these steps below):

sudo apt-add-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install boot-repair

then I ran boot-repair and selected the first option:

sudo boot-repair

this showed the commands to type to remove the old grub and install a new one into the EFI partition created above; then it was possible to boot in the newly installed ubuntu, using the new grub in the new EFI partition;

then in ubuntu at the terminal prompt I typed

sudo update-grub

and now the windows was also added to the grub menu and everything works again, upon the next reboot both ubuntu and windows can now be selected in the grub menu

apparently to shut down windows without the dirty hibernation, need to type at a windows command prompt

shutdown /s

I deleted the ubuntu partition because I needed more space on the windows partition; I did this using Create and format hard disk partitions in windows - just click on start menu and type part; resizing of windows partitions should be done only from windows to avoid issues; so I resized the windows partition with a few extra GB;

luckily, I did not give all the free space that was left after deleting the ubuntu partition to windows;

so when I got the grub rescue error, upon the next reboot, the ls and set grub commands worked, but several other commands like chainloader, initrd or normal did not work; the problem was that although I did do a shutdown, windows tries to be smarter and second guess you and do a hibernate anyway, to enable a faster boot next time; so the disk was in a "dirty" inconsistent state and therefore could not be mounted, except in read-only mode which does not allow fixing anything, even using a live ubuntu usb drive, and therefore, could not fix/reinstall grub from the live ubuntu; this of course also means that windows cannot be started from grub; and naturally, the os-prober command from linux cannot find the windows system in this state either, not that it matters;

in my case, as I had free space available, I created a partition from linux, with the ubuntu live usb installer - without touching the windows partitions - and also created a new EFI partition for grub and sized it to 128MB for good measure, and installed ubuntu into the new partition using the live usb installer; it installed fine - but at the end it failed to install grub - because the windows was hibernated/dirty

so for this, I used the live ubuntu usb and installed boot-repair as follows at a terminal (ctrl+alt+t to open a terminal in ubuntu) (this is installed only in memory, not on disk, as it is a live ubuntu usb, so if you reboot, you need to redo these steps below):

sudo apt-add-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install boot-repair

then I ran boot-repair and selected the first option:

sudo boot-repair

this showed the commands to type to remove the old grub and install a new one into the EFI partition created above; then it was possible to boot in the newly installed ubuntu, using the new grub in the new EFI partition;

then in ubuntu at the terminal prompt I typed

sudo update-grub

and now the windows was also added to the grub menu and everything works again, upon the next reboot both ubuntu and windows can now be selected in the grub menu

apparently to shut down windows without the dirty hibernation, need to type at a windows command prompt

shutdown /s