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Re: "btrsquash" images (dracut dmsquash-live + btrfs-in-squashfs runtime)



On Mon, 2011-03-28 at 14:02 -0400, Will Woods wrote:
> Chris asked me about this on IRC so I thought I'd mention it here:
> 
> On Fri, 2011-03-25 at 14:35 -0400, Will Woods wrote:
> > Keep in mind that the image is actually two parts again - initramfs and
> > squashfs.
> 

This looks like a stripped down live-cd to me. How big does squashfs.img
become?

> I should be more careful about talking about splitting the images back
> up! Let me be clear: with this proposed image layout, loader is still
> very, very dead. The layout is like this:
> 
> Old: [loader] -> [stage2]
> F15: [anaconda runtime]
> New: [dracut] -> [anaconda runtime]
> 
> Note that we are *not* responsible for any of the code outside the
> anaconda runtime - which means we're still no longer responsible for
> anything that involves locating or mounting the anaconda runtime. 
> 
> All of that is completely up to dracut, which has far better debugging /
> tracing tools than loader ever did, plus a builtin shell, udev, LVM
> assembly tools, raid assembly tools, fairly robust networking, iSCSI
> setup, etc. 
> 
> > We can also save RAM on media installs (and boot.iso and USB-based
> > installs) by leaving the squashfs image on the media. And for every
> > other case, we can just use the concatenated Big Image like are now.
> 

Yes please, us low end people need a break. 

> This is pretty simple to set up - boot.iso would contain
> LiveOS/squashfs.img and the initramfs would have an /etc/cmdline that
> directs it to look for (e.g.) 
>   root=live:CDLABEL="Fedora 15"
> This would save another ~128MB RAM. The same technique could be applied
> for performing installs from external drives (USB sticks and the like).
> 

Again, great anything to save on the ram. This is very like the old run
from ram option on the older livecds, now you don't have to pass that
option at the boot prompt. In the case of media backed squashfs.img,
using uuid or label for the cmdline would the same as a livecd/usb does
now? 

> > If we keep those parts separate, PPC users could use dracut's
> > networking stuff to fetch the runtime image.
> 
> And this would be up to the sysadmin to set up, not us. We can default
> to booting from the combined image for the normal network case, but
> sysadmins are an ingenious lot; as long as we provide them separate
> images[1] they'll figure out how to make the corner cases work using
> dracut's capabilities.
> 
> -w 

Great idea,

Jerry



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