5 sec boot

david at lang.hm david at lang.hm
Mon Oct 6 13:13:07 EDT 2008

On Mon, 6 Oct 2008, pgf at laptop.org wrote:

> mitch wrote:
> > >
> > >  > On a related topic, I would like to see us start bundling the initrd
> > >  > into the kernel image.  It's certainly possible to do that with existing
> > >
> > > "into"?  i'd rather see it simply concatenated,
> > By "into", I mean "in the same file".
> >
> > The existing kernel mechanism that I have looked at involves using the
> > linker to bind the kernel with the initramfs, creating symbols that tell
> > the kernel the location and size.  See
> > Documentation/filesystems/ramfs-roofs-initramfs.txt , especially the
> > "Populating initramfs:" section.
> >
> > I don't have strong feelings about the mechanism that is used.  The
> > method that is already in the kernel source seems like a good choice
> > unless it has problems.
> i think a scheme which makes the kernel and initrd inseparable
> using tools available on the laptop wouldn't be optimal.  like
> you, i like having them in the same file, but if we can't figure
> out how to glue an external initramfs onto a kernel so that they
> can still be taken apart (so the initramfs can be easily
> modified, or perhaps reused with another kernel, easily), then
> i'd say we should go with deepak's suggestion of separate
> partitions for kernel and initrd.

it's not that hard to find where the filesystem image starts and 
extract/replace/modify it from there.

Tivo systems have been doing this for a _long_ time. they have two kernel 
partitions, two root partitions, etc with the kernel partition including 
the initial filesystem and the firmware checking the integrity of the 
kernel partition (and the software there checks the integrity of the root 

it works well for Tivo in the locked-down mode, and it's been easy for 
people to hack it once the firmware check is disabled

David Lang

> (this all assumes the performance win over simply reading from the
> filesystem is worth it, of course.  i'm currently assuming that it
> would be, even with a possible change in filesystem.)
> paul
> =---------------------
> paul fox, pgf at laptop.org
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