Re: loader/stage2 interaction

[Chris Lumens <clumens redhat com>]

>>> - Part of the last one... we should copy the stage2 image out of its
>>>   initial location.  My reasoning for this is still that it makes
>>>   error handling easier when the repo has trouble.  This requires
>>>   making the repo editor more useful too.
>>>
>>>   Problem:  This increases the memory requirements, which no one likes.
>>
>> Small is good, but which specific memory requirements are we talking about?
>
> I was thinking ramdisk. If one boots off CD or a hdd or a USB disk, there's 
> something approaching a real disk (at least) for stage2. If you want the 
> ability to remove the boot medium, then that has to be stored somewhere 
> else.
>
> The target disk would be nice, but that's not (reliably) available until 
> partitioning and filesystem layout is done.

Yes, exactly.  In the URL installation case, we download the stage2.img
and toss it into /tmp, which is a ramdisk.  We only have to do this if
they're booting off the network, as the CD has stage2 on it.  It'd be a
lot simpler to just always put the stage2.img into /tmp but that
increases the memory usage for everyone.  Right now we're only
increasing the memory requirements for people who are booting off the
network and using URL installs.

The memory usage of stage2 is something around 100 MB.  We move this to
the target filesystem as soon as it's available.  That now happens to be
before package selection and dependency solving, which is where we
really run into memory troubles.

- Chris