[Fedora-livecd-list] RFC- improving livecd installer efficiency

[Douglas McClendon]

Douglas McClendon wrote:
> Question:  Does the current livecd installer inefficiently write lots of 
> 0's to the destination drive that it doesn't need to?
> 
> I think it might.  The os.img on the F7 livecd is a 4G sparse file with 
> about 2.3G of data.  Anaconda's livecdcopy backend uses python's 
> os.read/write.  I would guess that that means that 4G of data is getting 
> written, when theoretically only 2.3G needs to.
> 
> The solution that comes to mind is this-
> 
> in livecd-tools, create the os.img as a 7G (or 700G??) sparse file.  
> Basically just way big.  Then take care to make the ext3fs be the exact 
> correct size for the data (i.e. 2.3G).  Then, in the initramfs, just 
> after mounting it (after snapshotting it), do a resize2fs to 7G (or 700G).

To clarify a bit- Clearly the resize2fs should probably happen during boot (long 
after initramfs).  No need to bloat the initramfs with resize2fs.

Also, the mechanism that comes to mind for the ext3fs creation is this-

Take the existing image built as is, but after final install, resize2fs it to 
the smallest possible (nearly), then truncate the file, then do the dd seek 
trick to re-sparsify it vastly larger.

Or perhaps just throw in an entire extra tarcopy of the system to a new fs image 
file created the exact right size from the beginning.  This is more work, but 
will possibly save space on any files that got created and deleted during the 
installation process.

-dmc