GRUB for Debian/Knoppix dual boot

[luiznetto]

After an unsuccessful Debian installation, I erased everything from my hard drive, partitioned and formatted it with GParted, and installed Knoppix. Knoppix works for me to a certain extent, but it has serious limitations - for example, my USB sound card doesn't work with Knoppix. So I intend to install Debian on top of Knoppix. I left 80% of the disk empty for that purpose.

But I have two questions for you. First, GRUB failed to install with the Knoppix. I am contacting the Knoppix Forum, but they take a long time to answer and that forum isn't very helpful. I'd rather use their version of GRUB, I don't like the look and feel of the GRUB that comes with Debian 10 (the letters are too small), but I will use it if I have to. So my question is, if I install Debian 10 on top of Knoppix, will GRUB be installed automatically to MBR? Will it put Knoppix automatically on the menu, or will I have to edit one of its configuration files? I've had Debian/Knoppix dual boot before, but it was done in a different way.

And the second question is, when I format the new partition to put Debian on it, what filesystem should I choose? Should it be ext4?

I deeply appreciate your help and thank you in advance.

[p.H]

So I intend to install Debian on top of Knoppix

Please explain what you mean by "on top of".

GRUB failed to install with the Knoppix

How then do you boot Knoppix ?

I don't like the look and feel of the GRUB that comes with Debian 10 (the letters are too small)

You can tune Debian's GRUB look and feel through /etc/default/grub.

will GRUB be installed automatically to MBR?

This question makes sense only with BIOS/legacy boot. With EFI boot, GRUB does not use boot sectors.
GRUB for BIOS is installed wherever you tell it to. It can be an MBR, or a partition boot record.

Will it put Knoppix automatically on the menu

It depends how Knoppix (which I have no experience with) boots. If it boots the usual Linux way using a kernel image (vmlinuz) and initramfs (initrd) and a standard filesystem in a plain partition, then os-prober should detect it and update-grub should add it to GRUB's menu.

when I format the new partition to put Debian on it, what filesystem should I choose? Should it be ext4?

Ext4 is the sensible default choice if you have no reason to choose another filesystem type.

[luiznetto]

Please explain what you mean by "on top of".

I mean side by side. Install Debian without uninstalling Knoppix. Have you ever heard of Linux/Windows dual boot? A lot of people do that. I want to do the same with Debian/Knoppix instead of Debian/Windows. As simple as that.

How then do you boot Knoppix ?

It boots like a live CD/DVD, without a boot loader. It goes straight into Knoppix, without showing a Grub menu first, the same way it happens when you boot the live Debian or the live Knoppix DVD.

I am pretty sure I need Grub for BIOS because my laptop (which is about 12 years old) still uses BIOS. Actually I had Debian 10 installed before, I had to erase it because I had problems with the fan, but I am pretty sure Grub was installed to MBR, as has always been the case with this laptop. I have vmlinuz in the /boot directory and init in the / (root directory), but couldn't find initramfs or initrd.

Thank you.

[p.H]

I mean side by side.

This is very different from "on top of". Quite the opposite, actually.

Have you ever heard of Linux/Windows dual boot?

Please don't be patronizing.

It boots like a live CD/DVD, without a boot loader. It goes straight into Knoppix, without showing a Grub menu first

Any bootable media, including CD/DVD, has to have a boot loader. CD/DVD often use ISOLinux. Not showing a boot menu does not mean there is no boot loader.
Even GRUB can be set up so that it does not show any boot menu.

I have vmlinuz in the /boot directory and init in the / (root directory), but couldn't find initramfs or initrd.

By default init is expected to be in /sbin in the root filesystem. It is expected to be in / in the initramfs filesystem, but then /boot/vmlinuz should not be present. I don't know how Knoppix works, so I cannot explain this.

[luiznetto]

Thank you very much, but you still haven't answered my question. So, in case Grub has actually been installed, how should I configure it so that it will display the menu during boot? How can I make sure Grub was installed?

And the other question is, if I now install Debian side by side with Knoppix, will Grub be installed automatically onto MBR? If not, what can I do to make sure it does, and shows both OSs that I have installed on the menu?

[sunrat]

The installer will ask which disk you want GRUB installed to, so tell it to install to which ever disk your computer has set as its first boot disk. GRUB should detect any other OSs you have installed and add them to its menu.