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


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.


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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:



xz --format=lzma


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  • 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.



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  • 6 months later...
  • 3 years later...

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