suggestion: rescue boot extension

Richard W.M. Jones rjones at
Thu Jun 3 09:56:56 UTC 2010

On Wed, Jun 02, 2010 at 04:04:18PM -0500, Michael Cronenworth wrote:
> Eric Sandeen wrote:
> > Is it better to have a separate volume for this, or to just have a sort
> > of rescue initramfs ...?
> >
> > Seems like the latter is more flexible but then I'm no boot process wizard.
> Good suggestion.
> Another one: What about LVM snapshots? and/or btrfs snapshots?
> Either way would be less wasteful than a whole partition that would be 
> obsolete in a few weeks and may or may not have to deal with byte 
> growing pains if the initial size is too small years down the road.

I would like to note here that Windows Vista and later "solves" this
problem by stuffing a multi-megabyte rescue binary into the sectors
before the first partition.

One consequence of this is that the first partition starts at some
ridiculously large offset, and another is that if you don't copy this
"hidden" unpartitioned data between the boot sector and the first
partition, then you can end up with an unbootable Windows system.  I
found this out the hard way when writing virt-resize.  But at least it
doesn't require a precious primary partition :-)


Richard Jones, Virtualization Group, Red Hat
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