CentOS 6.5 initrd cannot open root device
 

Hi All,

I need to build an install CD with a few customizations and need to add some file to initrd.img. But when I create an initrd.img using what came with the CentOS 6.5 install disk, even without any additions, simple extraction and re-packing it doesn't boot.

Here's what I did, please let me know if anyone knows what could be
wrong.

CentOS 6.5 mounted on /mnt/iso
Extracted the initrd.img that came with the CentOS install disk
$ mount -o loop CentOS-6.5-x86_64-bin-DVD1.iso /mnt/iso
$ mkdir tmp
$ cd tmp
$ cp /mnt/iso/isolinux/initrd.img initrd.img.xz
$ xz -d initrd.img.xz
$ cpio -id < initrd.img
$ rm initrd.img
$ find . -depth -print | cpio -o -H newc > ../initrd.img
$ cd ../
$ xz --format=lzma -9 initrd.img

This results in results in initrd.img.lzma. I copied all data from /mnt/iso into a new directory (release) (using rsync) and copied the above initrd.img.lzma as release/isolinux/initrd.img. And created a bootable disk using mkisofs.

The boot fails saying:
VFS: Cannot open root device "(null)" or unknown-block (253,0)

If I just copy the original initrd.img to the release/isolinux/initrd.img and create the install disk it boots fine. I can't quite understand what happens when I extract and re-pack the file that it starts booting.

It may have something to do with the root option in your boot-loader. It needs to have the image defined as well.