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Re: [Xen-users] booting domU with multiple concatenated ramdisks?

To: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Subject: Re: [Xen-users] booting domU with multiple concatenated ramdisks?
From: Ferenc Wagner <wferi@xxxxxxx>
Date: Wed, 02 Apr 2008 15:26:15 +0200
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Mark Williamson <mark.williamson@xxxxxxxxxxxx> writes:

>> Some bootloaders (eg. syslinux) have to ability to load multiple
>> ramdisks, effectively concatenating them.  This makes it very easy
>> to augment ramdisks, like eg. customizing an installer.  Can I do
>> something similar with XEN?  Separating the ramdisk cpio arhives with
>> commas in the config file didn't work...
> I don't think this is currently possible.  There was some work done by a 
> developer in adding the ability to load multiple modules with the domain 
> builder (for supporting GNU HURD) but I don't know what happened to it.  I 
> don't *think* it was actually checked in.
> What do you actually require here?  Do you *literally* just need 
> concatenation 
> of the ramdisks in memory?

Yes, pretty much.  Basically, I'd like to have an easy means of
dropping random files into the ramdisk.

> Some metadata too?

I don't understand this, but probably no.

> It's probably not very hard to hack pygrub to build a compound
> "ramdisk" image containing the concatenated contents of multiple
> files (possibly with some other goop in there) in a file, then pass
> *that* to the domain builder.  It would be harder to modify the
> domain builder itself to load multiple files directly.

It's mostly trivial either way, right now I worked around by
decompressing both cpio archives, concatenating the compressing the
result again.  That effectively merges their contents behind the back
of the boot loader (or domain builder).  It's just somewhat
inconvenient when one has to test lots of different modifications one
after the other.

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