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Old 02-05-2014, 08:27 AM   #1
embLinux
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Lightbulb Want to understand Buildroot - the 3 compression modes


Hi there,

I'm using buildroot to generate my images and for sure there is the option of compression with the help of different methods (LZO, LZMA, gzip, ...).

So far i found these 3 compression options in buildroot (v. 2013.11):

- Kernel compression Mode (in make linux-menuconfig)

- Built-in initramfs compression mode (in make linux-menuconfig)

- Compression method for the .cpio root filesystem ( (in make menuconfig)

my questions are:
1 ) what is the difference of these modes (like is just the kernel compressed? is the whole image at once compressed, and where are the pros and cons between these 3 mentioned modes) and
2 ) why am I forced to chose between 3 methods for the kernel compression, instead of leaving it uncompressed ?

greetings

Last edited by embLinux; 02-05-2014 at 08:57 AM.
 
Old 02-24-2014, 01:59 PM   #2
Mara
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Those options are in fact three different ones. The first is of the compression of the kernel itself and it's the only one that deals with the kernel itself. The second is about the compression of the file system included in the kernel image (the kernel image may be compressed or not). The third option is about the additional file system. I'd recommend you to compress at least the external file system if you have one: this one may be really big if you choose to install too many packages.
 
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Old 02-25-2014, 01:56 AM   #3
embLinux
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Thank you, that explains my first question.

But is there a reasonable issue to be forced to compress a kernel instead of leaving it uncompressed? I can't think that this can be some kind of a bug.
 
Old 02-25-2014, 07:00 AM   #4
sundialsvcs
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I believe that it is fairly routine to compress the kernel, and that it is often necessary to compress "initramfs" because (IIRC ...) architecturally it was "a 3-1/2-inch floppy disk drive."
 
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