Re[2]: [uml-user] tmpfs-based root filesystems (aka diskless) under UML...

[Rob F. <rf...@ke...>]

On Sat, 29 Dec 2001 09:46:36 -0500
Jeff Dike <jd...@ka...> wrote:
>.  I've never had cause to figure out what an initrd image is supposed
> to do or how it's supposed to do it.
A normal way to use it is:
On another machine make a blank file i.e. with dd if=/dev/zero of=fs
count=4000 bsize=1k
mkfs a filesystem on this file this file, i.e. mkfs fs
loop mount the file: mkdir mnt; mount -o loop fs mt
copy a filesystem into this  file (for example get a copy of tomsbtr and
copy -a it, I use a busybox and uClibc built disk).
unmount and gzip it to make fs.gz
then fire up ye old unix kernel with the initrd compiled in and initrd=fs.gz
ramdisk_size=4000 root=/dev/ram0 init=/linuxrc as arguments.
The kernel will create a ram disk, then uncompress the fs.gz directly
into it as an image. Once this is done, the ram disk will have a
filesystem in it. The kernel will then mount this fileystem as the root
and, under instruction from the command line will execute the linuxrc
file which kicks starts the whole process. 
(That's where I create the shm filesystem and pivot).

-- 
Rob Fowler rf...@ke...