I had a problem with Ubuntu, it became slow after I got a message saying that a partition was full. So I opted to resize the partition.
So recently I installed Windows 10 in my laptop. The OS (Windows 10) ended up overwriting my ubuntu bootloader. So I created a USB bootable disk for Xubuntu, then I resized and moved the partitions I had on Ubuntu without any consideration of the messages I got saying moving a partition might corrupt a partition and make the Ubuntu OS not boot. Then I used the terminal to reinstall grub. I used:
$ sudo mount /dev/sda6 /mnt/boot \#which is where my boot partition
$ sudo grub-install --boot-directory=/mnt/boot /dev/sda
Then I restarted my computer. It brought me to the grub menu as usual but past that it stops at error: kernel panic unable to mount the root fs.
Then tried to use boot-repair, but it did not help. The boot-repair application save its info here.