kernel [vmlinuz] and initrd image [initrd.img]

• vmlinuz- is the "linux kernel"

• initrd is the "initial ramdisk"

It is enough files stored in a ramdisk to store needed drivers . You need the drivers so that the kernel can mount / and kick off init.

Remove old linux kernel entries from GRUB2 

 GRUB 2 has three main parts:

•     /etc/default/grub - the file containing GRUB 2 menu settings.

•     /etc/grub.d/ - the directory containing GRUB 2 menu creating scripts.

•     /boot/grub/grub.cfg - the GRUB 2 configuration file, not editable.

Steps 


1. /etc/grub.d/10_linux Identifies kernels on the root device for the operating system in use and creates menu entries.


Note: All kernels residing in the boot folder are included in this section. If you don't want all your old kernels to appear in the menu, remove the kernels from the /boot folder. 


2. Run grub-mkconfig


3. update-grub