Issue starting Ubuntu from Grub on 20.10

Solution 1:

Your initrd.img-5.8.0-59-generic ramdisk file is corrupt, and that's why you can't boot to the -59 kernel.

Loading Linux 5.8.0-59-generic ...
Loading initial ramdisk ...

See the file sizes and mod dates in the following two ramdisk files in /boot...

-rw-r--r-- 1 root root  54119063 Jul  5 19:46 initrd.img-5.8.0-55-generic
-rw-r--r-- 1 root root 115559351 Jul 16 20:44 initrd.img-5.8.0-59-generic

The fix...

Boot to the -55 kernel, open a terminal and type the following commands:

sudo update-initramfs -c -k 5.8.0-59-generic

ls -al /boot # confirm new file size for initrd.img-5.8.0-59-generic

reboot # to the normal -59 kernel

Update #1:

To check your file system...

• boot to a Ubuntu Live DVD/USB in “Try Ubuntu” mode
• open a terminal window by pressing Ctrl+Alt+T
• type sudo fdisk -l
• identify the /dev/sdXX device name for your "Linux Filesystem"
• type sudo fsck -f /dev/sdXX, replacing sdXX with the number you found earlier
• repeat the fsck command if there were errors
• type reboot