Difference between revisions of "Initramfs"

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How to inject a separate initramfs file into a 2.6 vmlinux (as section .init.ramfs):
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How to inject a separate initramfs file into vmlinux as section .init.ramfs.
  
First turn the initramfs into an ELF, excluding anything but the file data:
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First turn the initramfs into an ELF, excluding everything but the file data:
  
 
     objcopy -I binary -O elf32-i386 -B i386 --redefine-sym _binary_initramfs_start=.init.ramfs -N _binary_initramfs_end -N _binary_initramfs_size initramfs initramfs.elf
 
     objcopy -I binary -O elf32-i386 -B i386 --redefine-sym _binary_initramfs_start=.init.ramfs -N _binary_initramfs_end -N _binary_initramfs_size initramfs initramfs.elf
  
Note that the symbol names _binary_initramfs_{start,end,size} depend on the input filename. objcopy does some translation here, e.g. a period (.) in the filename will become an underscore (_) in the symbols.
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Note that the symbol names _binary_initramfs_{start,end,size} above depend on the input filename. objcopy does some translation here, e.g. a period (.) in the filename will become an underscore (_) in the symbols.
  
 
Now remove any existing .init.ramfs section in vmlinux and add the one in initramfs.elf:
 
Now remove any existing .init.ramfs section in vmlinux and add the one in initramfs.elf:

Revision as of 23:45, 6 August 2008

How to inject a separate initramfs file into vmlinux as section .init.ramfs.

First turn the initramfs into an ELF, excluding everything but the file data:

   objcopy -I binary -O elf32-i386 -B i386 --redefine-sym _binary_initramfs_start=.init.ramfs -N _binary_initramfs_end -N _binary_initramfs_size initramfs initramfs.elf

Note that the symbol names _binary_initramfs_{start,end,size} above depend on the input filename. objcopy does some translation here, e.g. a period (.) in the filename will become an underscore (_) in the symbols.

Now remove any existing .init.ramfs section in vmlinux and add the one in initramfs.elf:

   objcopy -I elf32-i386 -O elf32-i386 -R .init.ramfs --add-section .init.ramfs=initramfs.elf vmlinux vmlinux.withnewinitramfs

All done.