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Re: Proposal for low-mem cdrom install and minimum kernel versions thereof

On Tue, Oct 21, 2003 at 05:32:42AM +0200, Goswin von Brederlow wrote:
> Hi,
> debian-installer currently needs a lot of ram to install all the udebs
> on the cdrom. That was one reason for me to suggest mixing debix and
> debian-installer together into a live-cd install.
> So here is how it could work:
> -----------------------------
> 1. A small initrd is booted with enough stuff on it to find and mount
> the cdrom.
> 2. On the cdrom a huge initrd image is stored with all the udebs
> installed that anna would pull in of a cdrom anyway.
> 3. The huge initrd is loopback mounted and a lvm snapshot device is
> set over that with a ramdisk/tmpfs as copy-on-write storage.
> 4. mount the lvm snapshot on /mnt
> 5. transfere debconf database and other state files to /mnt
> 6. pivot-root over to the lvm snapshot and exec+chroot main-menu
> 7. continue as normal
> What have we won?
> -----------------
> The 20-40 MB ramdisk that would normaly be used will be kept on cdrom
> and only changes to that get stored to ramdisk on a block-by-block
> basis. No additional udebs would be installed into ram by anna unless
> choosen manually. The only big file left would be the Packages file
> which can probably also be preseeded on the cdrom.
> Apart from the ram, time is also saved. Installing all the udebs from
> cdrom takes a while on low-mem systems. Consider that an extra bonus.
> What needs to be changed for this?
> ----------------------------------
> - The device-mapper patch (kernel-patch-device-mapper.deb) would have
> to be included in a kernel image and the device-mapper tools (dmsetup)
> packaged as udeb.
> - When using tmpfs as storage 2.4.22 is the minimum kernel version.
> The benefit of tmpfs would be swapping capabilities once swap is
> initialized. Given this is for low-mem that might be nice. Using a
> ramdisk the lowest version is 2.4.19 I think.
> - rootskel-low-mem and busybox-low-mem versions would be needed
> - A pkglist and medialist per architecture. Two if there should be a
> cdrom wth and without base debs. But they would be just the
> cdrom-udebs/cdrom-base lists with the important udebs moved into the
> initrd. Could even be generated by the Makefile so only one list has to
> be changed in future.
> Think about it and let me know what you think. Try an d-i install with
> 64MB, 32MB or even 16 MB ram.

This sounds like a great idea to me. I am adding a low-memory test to
my list, to see how the current installer does. There are a lot of 
older machines out there that we're leaving behind if we require 32MB.

Debian GNU/Linux Operating System
  By the People, For the People
Chris Tillman (a people instance)
   toff one at cox dot net

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