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LZMA bzroot compression

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Does anyone know how to compress the bzroot with lzma/xz? I've tried using the same syntax as gzip but it's not working :(

 

decompression with

xzcat /path/to/bzroot | cpio -i -d -H newc --no-absolute-filenames

works fine but compression using the assumed

find . | cpio -o -H newc | xz > /path/to/newbzroot

or

find . | cpio -o -H newc | xz --stdout - > /path/to/newbzroot

creates a new archive but chokes on reboot when trying to extract the initramfs.

 

The boot chokes with:

VFS: Cannot open root device"(null)" or unknown-block(8,2)
Please append a correct "root=" boot option" here are the available partitions:

compressing the same data using gzip works fine though.  Makes me think I'm doing something goofy with the compression  :o

 

Using 5.0rc3 and I've attached a screenshot of the kernel puking all over the place.

Kernel_panic.jpg.87da96e895ce5384cdad3a5ba60fd0ff.jpg

Did you enable the proper compression support in the linux kernel config?

 

Try using "lzma" located in /usr/bin. It's the same as invoking 'xz' with the lzma option:

lzma

or

xz --format=lzma

 

  • Author

ANNNNND epic faceapalm! ::) I was compressing to xz not to lzma.  Sometimes it pays to step back and take a break and have fresh eyes take a peek.

 

Appreciate it brit!

  • 2 weeks later...

To further this a bit, I saw with the compression change done in 5RC that we now need to use the following to extract bzroot:

 

xzcat /path/to/bzroot | cpio -m -i -d -H newc --no-absolute-filenames

 

Do we need to use a new command to compress?  What should we use with the new releases?

 

I seem to be having issues with this as the original RC4 file is about 32Mb and when I compress it jumps to 40Mb.

 

Thanks!

rmilanov, read the thread you posted in. It has the answers. ;)

 

The new command is "xz --format=lzma" or "lzma".

Ok... if that's correct then I will continue using it.  I was just concerned because when I used those my bzroot came out 8Mb larger when I barely added anything to the image.

 

R

Odd. Not sure why it would be that much larger.

 

find . | cpio -o -H newc | xz --format=lzma > /path/to/newbzroot

  • Author

It could have to do with the default compression level.  Not sure what Limetech uses when he compresses the kernel. Any compression with lzma will end up better than .gz though :)

try

 

find . | cpio -o -H newc | xz --check=crc32 --x86 --lzma2=preset=9e > /boot/new_bzroot

 

  • 6 months later...

try

 

find . | cpio -o -H newc | xz --check=crc32 --x86 --lzma2=preset=9e > /boot/new_bzroot

 

I tried this and my bzroot went from 33MB to 65MB :/ I changed a few lines of text in two files. How could it go up so much!?!?

  • 3 years later...

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