switch_root and centos

Michael Di Domenico mdidomenico4 at gmail.com
Mon Dec 14 03:30:58 UTC 2009

Can anyone point me towards a how-to that shows step by step how to
boot up busybox and then switch_root to Centos installed on a local
hard drive and start that up?

After messing with busybox for a few days, i've gotten it to pxe boot
and run inside QEMU, but i'm having the hardest time getting
switch_root to startup Centos fully

The first problem i hit is the infamous "not rootfs", which i can see
is controlled by conditions, though have no idea which one i'm failing
on (a more verbose error msg would have been nice).  I commented out
the conditions and it does seem to pivot root, but doing

exec switch_root /newroot /etc/rc.d/rc.sysinit

looks like things are going to startup and it pushes through some of
the sysinit scripts, but then dumps me back into busybox

Which led me to believe its not really invoking /sbin/init, but when i do

exec switch_root /newroot /sbin/init 3

I get 'timeout opening/waiting for initctl'

I'm really at a loss to understand what's not working and googling
hasn't turned up any revelations

Here's my busybox init script



mount -t proc proc /proc
mount -t sysfs sysfs /sys
mount -t tmpfs tmpfs /dev

echo "Creating initial device nodes"
mdev -s

echo "Loading jbd.ko module"
insmod /lib/modules/jbd.ko
echo "Loading ext3.ko module"
insmod /lib/modules/ext3.ko
echo "Loading scsi_mod.ko module"
insmod /lib/modules/scsi_mod.ko
echo "Loading sd_mod.ko module"
insmod /lib/modules/sd_mod.ko
echo "Loading libata.ko module"
insmod /lib/modules/libata.ko
echo "Loading pata_sis.ko module"
insmod /lib/modules/pata_sis.ko
echo "Loading sata_sis.ko module"
insmod /lib/modules/sata_sis.ko
echo "Loading ata_piix.ko module"
insmod /lib/modules/ata_piix.ko
echo "Loading mii.ko module"
insmod /lib/modules/mii.ko
echo "Loading e1000.ko module"
insmod /lib/modules/e1000.ko
echo "Loading sis900.ko module"
insmod /lib/modules/sis900.ko

mount /dev/hda /newroot
exec switch_root /newroot /sbin/init 3

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