[Fedora-livecd-list] The long-awaited landing of persistence
Jeremy Katz
katzj at redhat.com
Thu Mar 6 20:38:32 UTC 2008
On Thu, 2008-03-06 at 15:20 -0500, Warren Togami wrote:
> Jeremy Katz wrote:
> > The quick steps of how to take advantage of the functionality:
> > 1) Build a live image using the newer mkinitrd (6.0.32) in your repos
> > 2) Use the updated livecd-iso-to-disk.sh with an --overlay-size-mb=512
> > (or 1024 or whatever based on the capacity of your USB stick minus the
> > size of the ISO)
>
> if [ -n "$overlaysizemb" ]; then
> echo "Initializing persistent overlay file"
> OVERFILE="overlay-$( /lib/udev/vol_id -l $USBDEV )-$(
> /lib/udev/vol_id -u $USBDEV )"
> dd if=/dev/null of=$USBMNT/LiveOS/$OVERFILE \
> count=1 bs=1M seek=$overlaysizemb
>
> Warning!
>
> If your USB stick is vfat filesystem and $overlaysizemb is
> some number larger than your RAM, your system will swap storm and die.
> According to Ulrich Drepper this isn't dd using all RAM, but it is up to
> the filesystem implementation. Since the OOM happens in kernel space it
> cannot OOM kill anything and recover.
>
> I just tried the same thing with the USB stick reformatted as ext3. It
> successfully created the sparse file without any problem.
>
> Perhaps this means we cannot support overlay images on vfat?
Or we may need to limit the size that we support. Warren and I are
looking a little closer now...
Jeremy
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