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Discover the Anatomy of initrd
IdaAshley writes "The Linux initial RAM disk (initrd) is a temporary root file system that is mounted during system boot to support the two-state boot process. It contains various executables and drivers that permit the real root file system to be mounted, after which the initrd RAM disk is unmounted and its memory freed. In this article explore the initial RAM disk for Linux 2.6, including its creation and use in the Linux kernel. In many embedded Linux systems, the initrd is the final root file system."
This looks to be a pretty good tutorial.
As well as mkinitrd, there are some cool tools coming along that help build an initrd.
Here is one I have used, and although it's very early in it's development cycle.
http://yaird.alioth.debian.org/
Are there any more that are actually easy to use?
Signature v3.0, now with 42% less memory usage.
You're right. Initramfs is better in many ways to initrd, and doesn't have the crazy limitations.
Initramfs, IIRC, has these advantages:
It doesn't need block level drivers compiled into the kernel to read itself like initrd does.
It uses the kernel cache area as its file storage area so you don't have to allocate space with a ramdisk.
The mem it used to store files with temporarily can be returned to the kernel after the kernel has booted.
No artificial size limit.
All in all, it's a much better alternative.