Livecd from ram

Phillip Susi psusi at
Sat Dec 24 17:17:07 GMT 2005

I've been kicking this idea around for a while now in my head and now 
I'd like to get some more opinions.  I think that the livecd would 
perform much better if the cloop/cramfs image is copied to a tmpfs at 
boot time and mounted from there.

What about systems without enough ram to hold the whole image?  The most 
common use cases of the livecd will be in a system that has a hard drive 
that already either has a linux system or windows installed.  If the 
system already has a linux system installed, there will be a linux swap 
partition that can be used.  If windows is installed, then I thought 
hey, windows has a pagefile already on the disk, simply using that 
shouldn't be too hard right?

The initramfs on the livecd could first probe for a linux swap 
partition, and if not found, then check all fat and ntfs partitions for 
a windows pagefile.  Even if it is on an ntfs partition, you can still 
get the block list that the existing file lives in and bypass the 
filesystem to swap to the pagefile.  You would need to skip the windows 
pagefile header, but the rest of the file could be turned into linux 
swap space.  This could be done with a small utility to get the block 
list and set up a kernel device mapper device mapping the pagefile, then 
mkswap and swapon that dm device.

With some usable swap space, even mid to low memory systems could copy 
the livecd image to the swap space and then running from there should be 
much faster than from the cd.  Of course, in the event that no swap is 
found, the system will run like it does now, and the user can use a boot 
parameter to force one way or the other.  What do you guys think?

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