[CentOS] PXE-Kernel crashes with "RAMDISK: incomplete write ..." after modifiying initrd.img

Thu Mar 26 16:41:55 UTC 2009
Frank Thommen <frank.thommen at embl-heidelberg.de>

>> to install current PC models (with new Intel NICs) via Kickstart/PXE, I
>> wanted to add the newest e1000e-Treiber to initrd.img.  With this
>> modified image, the Kickstart kernel crashes with the following error
>> messages:
> Maybe you need to increase the memory allocated to ramdisk? by
> default I use ramdisk_size=16384 as a kernel parameter for booting
> the installer.

with ramdisk_size=16384 the error message is:

md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
RAMDISK: Compressed image found at block 0
RAMDISK: incomplete write (-28 != 32768) 16777216
VFS: Cannot open root device "<NULL>" or unknown-block(253,3)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on

There is probably an exact way to determine a valid ramdisk_size, buth 
which? :-}