Re: Migrations to xorriso

[Seth Goldberg]

Quoting Vladimir 'φ-coder/phcoder' Serbinenko, who wrote the following on...:

> Thomas Schmitt wrote:
> > Hi,
> >
> > Isaac Dupree wrote:
> >
> > > What size range are the whole images?
> >
> > The minimum output of grub-mkrescue 1.98 with
> > xorriso is 1544192 bytes.
> > grub-mkisofs: 1550336
> > genisoimage:  1859584 (-307200 with -no-pad)
> >
> > One may add lots of other files, of course.
> >
> >
> >
> > > Also I guess no one compresses whole ISOs
> >
> > It makes few sense to compress the ISO as a
> > whole. But one could compress some files in it.
> >
> > One could implement a reader for H. Peter Anvin's
> > zisofs format in GRUB's ISO 9660 reader - if not
> > present already.
> > zisofs is a transparent content compression of
> > single files. A reader is implemented in the
> > Linux kernel. See macro CONFIG_ZISOFS in
> > fs/isofs/*.[ch].
> > An authorised description is given in
> > doc/zisofs_format.txt of xorriso resp. in
> >   
> > http://bazaar.launchpad.net/~libburnia-team/libisofs/scdbackup/annotate/head:/doc/zisofs_format.txt
> > The ISO 9660 directory tree stays uncompressed.
> > Compressed and uncompressed files can be mixed.
> >
> > xorriso can produce zisofs compressed data files
> > on the fly (needs zlib).
> > A grub-mkrescue 1.98 image with all files
> > compressed has 884736 bytes. But one would have
> > to leave those files uncompressed which are
> > needed for reading ISO 9660 and zisofs
> > compression.
> I'm not sure that zisofs is useful for grub. We already have support for
> .gz files. xz support is coming. Compressing explicitly we would avoid
> to accidently compressing files we need uncompressed. Also we're more
> fs-independent.
> Implementing zisofs reader may have some value but isn't a priority.

 For the record, Solaris uses a ISO9660 filesystem image with individual 
compressed files, but this is mainly useful for being able to have a boot 
archive that grub2 does not have to completely decompress before loading 
into memory (so we get the benefit of a nearly-compressed filesystem image) 
without the overhead (taking the overhead on read operations).  The value to 
grub2, though, is unknown.

 --S