[Fedora-livecd-list] Progress Report: Upping the 4gb filesystem limit

[Frederick Grose]

On Sun, Jun 17, 2012 at 6:25 PM, David Laban <alsuren at gmail.com> wrote:

> Just a heads up that I'm working on a couple of patches to
> livecd-iso-to-disk that let you up the filesystem limit.
>
> The current setup is:
>
> filesystem
> |_ livecd.iso
>   |_ squashfs.img --read-only?
>      |_ ext3fs.img
>
> I have prototyped it, and I had to:
>
> * cp --sparse=always ext3fs.img <filesystem with sparse support and
> 2.5GB free> // If I could mount the squashfs image read-write or do
> some kind of snapshot/overlay, this would be unneccesary
>
> * dd seek=8GB of=ext3fs.img
> * losetup ext3fs.img
> * resize2fs /dev/loopX // automatically expands to fill the whole
> 'partition' == 8GB
> * mkdir -p tmp/LiveOS/
> * mv ext3fs.img tmp/LiveOS/
> * mksquashfs tmp squashfs.img // takes ages: has to re-compress 2.5GB
>
> Can anyone give any hints on making this more efficient, or should I
> submit a patch to
>
> http://git.fedorahosted.org/git/?p=hosted/livecd;a=blob;f=tools/livecd-iso-to-disk.sh;hb=HEAD
> as it is?
>
> Also, I need to do more research into snapshots (had a wild goose
> chase grepping the kernel source for "overlay") but I think that I
> might be able to re-compact the overlay file into the squashfs using
> the above process. Would anyone be interested in seeing a patch of
> that form?
>

Yes, such a patch is feasible.
See
http://wiki.sugarlabs.org/go/LiveOS_image

for more information on the LiveOS image.

I have a version of edit-livecd,
http://git.fedorahosted.org/git/?p=hosted/livecd;a=blob;f=tools/edit-livecd;hb=HEAD
, which I call editliveos.py, that uses a virtual filesystem mirror to
merge the ext3fs.img with the overlay to create an updated, single
filesystem image file (instead of using rsync, as the current version does
with the --clone option).

(I haven't tested the rsync version in a long time, since it failed,
http://www.mail-archive.com/livecd@lists.fedoraproject.org/msg01052.html
, and I haven't seen other reports of its use.)

My current version of editliveos.py has a perplexing bug where an image
built from a live running source will reboot, but one built from an
attached LiveOS source fails to reboot.  This was not previously a problem,
and I suspect some side effect of the systemd startup changes on the way
new sessions or seats are authenticated.

The new version involves updates to fs.py, util.py, live.py, and creator.py
and I have not submitted patches yet for review, but I have just posted
whole files at
http://git.sugarlabs.org/soas/sugar-clone-extensions/commit/8c4e03323fc9a7e630e6c62213bb842909fbaa00

           --Fred


> Also, I think that pre-allocating 2GB from /dev/zero on FAT
> filesystems is pointless and needlessly slow. Doesn't the overlay grow
> itself anyway?


The overlay file is fixed in size.

Also, isn't the limit 4GB for FAT32?
>
> David.
> --
> livecd mailing list
> livecd at lists.fedoraproject.org
> https://admin.fedoraproject.org/mailman/listinfo/livecd
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