I installed slack with elilo in EFI mode.
The elilo.conf is simple and it loads vmlinuz without an initrd. It's straightforward.

In the case of loading a Xen-dom0 kernel I understand you have to use mobootpack to create a composite image for the elilo loader. But is an initrd still required in this case?

From memory, an initrd is only needed if the kernel doesn't have all necessary drivers compiled into it.

If the kernel was compiled using an initrd, you probably need it. If you compile your own, you can choose your options and do without it. I do. In booting, the following things happen

1. Bios starts reading the hard disk, and thus runs the boot loader
2. Boot loader loads kernel and initrd if specified.
3. Kernel takes over. It has to be equipped to handle every task it attempts with compiled in modules.
4. Kernel mounts root and the module tree becomes accessible.

So, obviously in the initrd or kernel, you need support for your hard disk filesystem, and motherboard chipset. In special cases you need access to decryption, or network or other exotic things. If /boot and / don't have the same filesystem, you need support for both. You don't need modules for networking, bluetooth and usb unless they're needed by the kernel in the boot process.

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https://en.wikipedia.org/wiki/Initial_ramdisk

I had to look it up.

Reason I asked was in the particular case of loading Xen.
If I understand correctly, Xen loads first then it chains vmlinuz. So the order in which modules load is:

- Xen
- initrd
- vmlinuz.

Do you mean you want to edit grub such as this?
"
Edit Debian's configuration file for grub-mkconfig.
# vi /etc/default/grub

Change the line:

GRUB_DEFAULT=0

to

GRUB_DEFAULT='Debian GNU/Linux, with Xen hypervisor'
"

I am now lost as to your question exactly? Do you mean when you start a dom?

1 members found this post helpful.

I was asking when starting dom0.

Nevermind, I think the question has been answered.

OK, sorry I didn't get the question.
Thanks for the update.

More info here just in case.

https://wiki.xenproject.org/wiki/Xen...eginners_Guide

The initrd copes with parts of the kernel that were compiled as "modules", but are REQUIRED to read the data necessary to boot. The initrd is optional if those parts of the kernel are NOT modules. Things like drivers for the hardware that contains the kernel (SATA / USB), and the filesystem(s) needed to read the kernel are required to NOT be modules if you do not have an initrd. All the other modules can be loaded after the fact via /etc/modules or /etc/modprobe.d/*.conf preferences.

Pros and cons of course, like not being able to unload modules and free resources if they are not modules. Like if /boot/ is it's own partition with a unique filesystem, which you don't need after booting. The module to read it will always be active if it's not a module (less RAM, fewer CPU cycles). One thing that annoys me about embedded systems like raspbian is that the nfs modules are NOT modules. I don't use that part of the kernel, but they take space and add entries to the output of ps (nfsiod+rpciod), which annoys me as I cannot remove them without recompiling the kernel and rebooting. And on older boards with only 256MB of RAM, that can be a significant cost to performance and functionality.

You do not need initrd if you have all modules, required to access root filesystem, built-in the kernel.
It is mean, that it is only for your own compiled kernel.