I want to use an uncompressed kernel image and boot the BeagleBoard. Generally I use uImage to boot the kernel which is in compressed format. How do I use an uncompressed kernel image?
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You are using U-Boot as the bootloader, right? – Gilles 'SO- stop being evil' Feb 06 '12 at 23:43
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yes! Is it possible using uboot? – Sharanya Feb 07 '12 at 05:56
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As far as I know, U-Boot cannot directly boot a “raw” ELF image (vmlinux). You need to turn it into the uImage format, which contains the compressed vmlinux plus a few extra bytes of metadata that describe the kernel load address. U-Boot FAQ 2.19 explains how to generate uImage; it's fairly straightforward, using the mkimage utility in the U-Boot source tree:
mkimage -A arm -O linux -T kernel -C gzip … -d vmlinux uImage
(You may need extra parameters indicating the load address.)
Gilles 'SO- stop being evil'
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1Uncompressing the uImage while booting takes some time. I need to minimize that. So i thought why dont i try with the uncompressed raw file vmlinux. – Sharanya Feb 07 '12 at 05:55
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3The effect you want to achieve might be opposite to intended. Decompression time is usually smaller than time of copying data from flash. – Matt Kucia Aug 25 '13 at 20:46
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If you are using ubifs for the root image, it is already compressed somewhat. – John Klug Jun 08 '21 at 17:28
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mkimage -A arm -O linux -T kernel -C gzip … -d vmlinux uImage
Change gzip in the above example to none, and you'll create a u-Boot compatible uncompressed image.
Jim Davis
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If you are using Buildroot, select a uImage kernel output file (BR2_LINUX_KERNEL_UIMAGE=y). Compile normally and Buildroot will also create a vmlinux file in an intermediate step. While the vmlinux file is not copied to the /output/images directory it can be found in ./output/build/linux-custom/(or by running find . -name "vmlinux").
