Tiny Core Linux Installation and Boot Menu Setup on Grub2-EFI

Tiny Core Linux is a wonderful tool to have as a backup system on a USB drive in case you ever need to do emergency repairs to your computer system.  It can also be a very lightweight and elegant  desktop system when installed to a hard drive.  My goal was to install to a small partition on my hard drive, and boot from the grub installation installed from my Debian Buster installation on another partition.

I followed the excellent installation instructions on the Tiny Core website at: http://tinycorelinux.net/install.html

I booted back into by Debian system and ran # update-grub , but the prober failed to find my Tiny Core installation.

Fortunately, Grub2 provides a way to add custom menu items to the boot menu.

First, I needed the UUID of the root partition of my Tiny Core installation, so I opened a root terminal and ran # blkid  The results included the partition I was interested in, which was: /dev/sda6: LABEL="tinycore" UUID="7a130a42-5c23-4148-80c9-c9a8e78f311c" TYPE="ext4" PARTUUID="c04ff9fd-76a7-4e19-be5f-588f230dd9f3"

Then, I need to know the locations of the  kernel and initrd files.  I can cheat a little because I know the files will be in the /tce/boot directory on the Tiny Core partition.  So, I take a peek at that directory with the command # mkdir tmp && mount /dev/sda6 tmp && ls tmp/tce/boot/ && umount tmp  && rmdir tmp

Which returns:
core.gz  extlinux  vmlinuz

In order to get Grub2 set up to boot Tiny Core, I edited the custom boot entry file.  To do this, I opened a terminal and ran the following (as root): # nano /etc/grub.d/40_custom

The file, 40_custom, looks like this before editing:

#!/bin/sh

exec tail -n +3 $0

# This file provides an easy way to add custom menu entries.  Simply type the

# menu entries you want to add after this comment.  Be careful not to change

# the 'exec tail' line above.

Without removing any text in the file, I added my entry at the bottom, adding the UUID for /dev/sda6 where appropriate.  I am using vmlinuz for the linux line and core.gz for the initrd line.  I didn't have any additional bootcodes I wished to pass, but those can be added to the end of the line that starts with "linux":

menuentry "Tiny Core on sda6"  {

insmod part_gpt

insmod ext2

set root='hd0,gpt6'

search --no-floppy --fs-uuid --set 7a130a42-5c23-4148-80c9-c9a8e78f311c

linux /tce/boot/vmlinuz root=7a130a42-5c23-4148-80c9-c9a8e78f311c

initrd /tce/boot/core.gz

}

I hit ctrl+x to save the file, then ran # update-grub.  I was a bit disappointed here because my entry did not show in the list of menu entries generated, but I rebooted anyway.  At boot, the custom entry was at the bottom of my Grub2 menu list, and I was off and running with Tiny Core