Date: Fri, 5 Sep 2003 23:53:04 +0100
From: Colm MacCarthaigh <colm@stdlib.net>
To: ilug@linux.ie
User-Agent: Mutt/1.3.28i
Subject: [ILUG] cramfs + initrd + Linux = headache

The Linux Kernel Developers are special people, they've broken cramfs
as an initrd 3 times now since 2.4.18, and we decided to abandon it and
now use ext2 initrd's for our Software RAID setups :)

Unfortunately since Debian's nice mkinitrd command just makes cramfs
by default you need to provide a program to take a directory and
build an image. Just such a script for ext2 is attached, a new
initrd can be made as;

 mkinitd -m `mkext2initrd %s %s` -r /dev/[thing is root] -o /your/initrd

Or if you just replace mkcramfs with the script, or modify
/etc/mkinitrd/mkinitrd.conf to match it's all good too.

Posted in the hope it saves someone else a whole heap of headache.

*waves hello if you're reading the archive and just got here from google*

--
Colm MacC=E1rthaigh                        Public Key: colm+pgp@stdlib.net
colm@stdlib.net					  http://www.stdlib.net/




#!/bin/bash

# mkext2initrd directory imagename
#
# - Make an ext2 initrd, colm.maccarthaigh heanet.ie
#   Contains bashisms

if [ ! -d "$1" -o -z "$2" ] ; then
	echo "usage: mkinitdrd directory imagename"
	exit 1
fi

# get an idea of the current usage
USAGE=`du -sb $1/ | awk '{print $1}'`
IMAGE=`mktemp`

# Create an empty file of the corresponding size + 20%
if ! dd if=/dev/zero of=$IMAGE bs=1 count=$(( $USAGE + $(($USAGE / 5)) )) \
   > /dev/null 2> /dev/null ; then
	echo "error creating $IMAGE"
	rm $IMAGE
	exit 1
fi

# Create the filesystem
if ! yes | mkfs.ext2 $IMAGE > /dev/null 2> /dev/null ; then
	echo "error creating filesystem on $IMAGE"
	rm $IMAGE
	exit 1
fi	

# Mount it over loopback
if ! mount -oloop $IMAGE /mnt ; then
	echo "error mounting filesystem, $IMAGE"
	rm $IMAGE
	exit 1
fi

# Tar stuff
if ! tar -C $1 -cpf - ./ | tar -C /mnt -xpf - ; then
	echo "error untarring"
	rm $IMAGE
	exit 1
fi

# umount
if ! umount /mnt ; then 
	echo "error unmounting"
	rm $IMAGE
	exit 1
fi

# gzip
if ! gzip -n -9 $IMAGE -c > $2 ; then
	echo "error compressing $IMAGE to $2"
	rm $IMAGE
	exit 1
fi

# Remove the image
rm $IMAGE





Date: Sat, 6 Sep 2003 00:13:36 +0100
From: Colm MacCarthaigh <colm@stdlib.net>
To: Ronan Cunniffe <ronan@cunniffe.net>
Subject: Re: [ILUG] cramfs + initrd + Linux = headache
Cc: ilug@linux.ie

On Sat, Sep 06, 2003 at 12:02:25AM +0100, Ronan Cunniffe wrote:
> Quoting Colm MacCarthaigh <colm@stdlib.net>:
> >
> > The Linux Kernel Developers are special people, they've broken cramfs
> > as an initrd 3 times now since 2.4.18, and we decided to abandon it and
> > now use ext2 initrd's for our Software RAID setups :)
>
> >  mkinitd -m `mkext2initrd %s %s` -r /dev/[thing is root] -o /your/initrd
>
> What's wrong with the usual loopback/ext2 scheme?

What do you mean usual? The usual Debian way is to create a cramfs initrd,
this script basically provides an ext2 over loopback scheme.

So in that sense, there's nothing wrong with a lookback/ext2 scheme,
this is one!

All this script does is allow you to use one with Debian's mkinitrd,
which handles all the nasty details of building a useful / directory,
putting in the raidtools, creating a modules heirarchy  and all that
kind of messing about for you.

--
Colm MacCarthaigh                        Public Key: colm+pgp@stdlib.net
colm@stdlib.net					  http://www.stdlib.net/