livecd and pxe boot memory footprint

[Phil Meyer]

The livd images currently appear to have 4GB filesystems, which would 
correspond to single layer DVDs. This is ok.

My question: Is the entire free space reported bf tools like 'df' writable?

My simple tests indicate that it is not.

ie:

# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop6 4.0G 1.3G 2.7G 33% /
05:40 PM Tue Sep 27
# wget 
http://mirror.fiber.net/centos/6.0/isos/x86_64/CentOS-6.0-x86_64-bin-DVD1.iso
--2011-09-27 17:41:04-- 
http://mirror.fiber.net/centos/6.0/isos/x86_64/CentOS-6.0-x86_64-bin-DVD1.iso
Resolving mirror.fiber.net... 69.160.84.36
Connecting to mirror.fiber.net|69.160.84.36|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 4238800896 (3.9G) [application/octet-stream]
Saving to: “CentOS-6.0-x86_64-bin-DVD1.iso”

12% [===> ] 529,255,008 721K/s in 13m 11s


Cannot write to “CentOS-6.0-x86_64-bin-DVD1.iso” (Read-only file system).

# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop6 4.0G 1.8G 2.2G 46% /

So it seems that roughly 500MB is available via an overlay.

Only 'livecd-iso-to-disk', of all of the livecd tools, has an overlay 
option.

The question is:

How to adjust the overlay somewhere during the process of:

livecd-creator -> livecd-iso-to-pxeboot

such that a system using that initrd.img has all of the remainder of the 
4GB file-system available via the overlay.

Thanks for any pointers!

<Cross Posted>