how_to_modify_initrd.img_and_recreate_it

                   How to Modify initrd.img and Recreate it
Abstract
========
  This guide documents how to modify an Initial Ramdisk Image, and recreate it.

Contents
========
  1. Extract initrd.img
  2. Modify the Contents of initrd.img
  3. Recreate the initrd.img

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1. Extract initrd.img
=====================

# initrd.img is in gzip format, we first rename it to initrd.gz
$ mv initrd.img initrd.gz

# Unzip initrd.gz using gunzip, and we get the file "initrd"
$ gunzip initrd.gz

# The file "initrd" is in cpio "newc" format, which can be extracted using cpio
$ mkdir initramfs && cd initramfs
$ cpio -id < ../initrd

# Now, the contents of initrd.img are in dir "initramfs"
$ ls

2. Modify the Contents of initrd.img
====================================

Based on your requirements, make some changes ...

3. Recreate the initrd.img
==========================

$ cd ..
$ find initramfs | cpio --create --format='newc' > initrd
$ gzip initrd
$ mv initrd.gz initrd.img