Re: How to use xzio?

[szymon]

On Mon, 27 Dec 2010 22:58:18 -0800 (PST), Seth Goldberg 
<address@hidden> wrote:
> Hi,
>
>   I'm trying to experiment with loading xz-compressed multiboot
> modules and cannot figure out how to do it so that the xzio module 
> can
> actually deal with the compressed file (after instrumenting it, the
> problem is "unsupported xz options"),  I've tried simply compressing
> the file I'm interested in loading with "xz", and with "xz -1" and
> both of the files cannot be decompressed. What's the deal with the xz
> support, then?

xzio utilizes xzembedded for decompression and this implementation 
doesn't
support crc64 (which is default in xz). So one must compress files with
xz --check=crc32 foo.bar  or  xz --check=none foo.bar

It also supports BCJ filters (only with start offset=0) so if you are 
compressing
executable code better compression ratio (few %) can be achieved
xz --x86=start=0 --lzma2 --check=crc32 foo.bar
(also supports PowerPC, ARM, ARM-Thumb, IA-64, SPARC code, see xz 
manual for details)


Maybe xzio should print appropriate warning when unsupported (but not 
critical
for decompression) option is used?

> Also, the grub manual currently only lists gzip:

Yeah... I'll update documentation with xz stuff when find some time :)

--
Szymon Janc