how modify initramfs...init script

Hello , all
In linux boot process when using initramfs..
I dont want to use real rootfilesystem ..
I want to continue working on root filesystem on ram disk ..also want to have ability to read/write CF disk..
I am booting linux from CF disk , havind minimal debian 4.0 system on it....
any help / reference will do !!
thanks in advance

Take a look at the file Documentation/filesystems/ramfs-rootfs-initramfs.txt in the linux directory.

Basically, what I did to get this working was to create a directory containing all files for the initramfs and a file describing my initramfs and point to that file in the kernel configuration. You have to provide an /init file in your initramfs, I used a symlink to busybox for that purpose and then I created an /etc/inittab with an entry for my start script. I don't know how this will work in Debian though.

ugglan,
Thanks for the pointer, I was going to post a similar/related question. Funny, I was looking for "initxxx" in the filesystems directory, never thought to look under ramxxx

How to View, Modify and Recreate initrd.img

Question: How do I view, modify and recreate the new initrd.img on Ubuntu, Debian, CentOS, Fedora, Red-Hat, Arch Linux, or SUSE distributions?

1. How To View Content Of initrd.img file?

initrd.img is in gzip format. So move initrd.img to initrd.gz as shown below.

# cp /tftpboot/el5/initrd.img .

# ls
cdrom initrd.img

# mv initrd.img initrd.gz

Unzip the initrd.gz file as shown below.

# gunzip initrd.gz

# ls
cdrom initrd

After unziping the initrd.gz file, the initrd is further in cpio ‘newc’ format. So extract the files from initrd using cpio ‘newc’ format as shown below.
Note: info cpio will give more information about ‘newc’ format.

# mkdir tmp2

# cd tmp2/

# cpio -id < ../initrd
16524 blocks

Now you can view the content of initrd.img file

# ls
bin dev etc init modules proc sbin selinux sys tmp var

2. How To Modify Content of Image and Recreate New Image?

After extracting the file as shown below, make appropriate modification to any of those files. Then pack the files back into the archive using the following commands. Pack the modified files back to cpio ‘newc’ format.

# find . | cpio --create --format='newc' > /tmp/newinitrd
16524 blocks

# ls /tmp/
cdrom initrd newinitrd tmp2

# ls -l /tmp/newinitrd
-rw-r--r-- 1 root root 8460288 Jul 2 14:50 /tmp/newinitrd

Gzip the archive file.

# gzip newinitrd

# ls
cdrom initrd newinitrd.gz tmp2

# ls -l newinitrd.gz
-rw-r--r-- 1 root root 6649867 Jul 2 14:50 newinitrd.gz

Move file as an image file. You can use the newinitrd.img as your new boot image.

# mv newinitrd.gz newinitrd.img

# ls -l newinitrd.img
-rw-r--r-- 1 root root 6649867 Jul 2 14:50 newinitrd.img