Easy enough to get an initrd into the Linux kernel, one simply has to make the rootfs and select the kernel option initrd source. That's all fine and dandy but can one pull this out of the kernel?

I did a cursory search of the web, but couldn't find anything about it.

I have an old kernel image that I need to pull apart, but I don't have the rootfs that was the initrd. Short of booting the kernel and tar bz2'ing the file system, is there a way to extract it?