Emulating Android JB on QEMU -

i've been trying build , run android jellybean on qemu.
have kernel built target machine type (arm versatile express - cortex a15)

i have been trying build qemu image output of android build end errors such as
qemu-system-arm -serial stdio -m vexpress-a15 -m 128m -kernel zimage -append "root=/dev/sda1 earlyprintk" android_jb.img

<3>vfs: unable mount root fs via nfs, trying floppy.
vfs: cannot open root device "/" or unknown-block(2,0)
please append correct "root=" boot option; here available partitions:
<0>kernel panic - not syncing: vfs: unable mount root fs on unknown-block(2,0)

this happens if don't specify -initrd option qemu.

when specify initrd option
qemu-system-arm -serial stdio -m vexpress-a15 -m 128m -kernel zimage -append "root=/dev/sda1 earlyprintk" -initrd ramdisk.img android_jb.img (generated android build process), following errors

<3>init: cannot find '/system/bin/servicemanager', disabling 'servicemanager'
<3>init: cannot find '/system/bin/vold', disabling 'vold'
<3>init: cannot find '/system/bin/sh', disabling 'setconsole'
<3>init: cannot find '/system/bin/netd', disabling 'netd'
<3>init: cannot find '/system/bin/debuggerd', disabling 'debuggerd'
<3>init: cannot find '/system/bin/rild', disabling 'ril-daemon'
<3>init: cannot find '/system/bin/surfaceflinger', disabling 'surfaceflinger'
<3>init: cannot find '/system/bin/app_process', disabling 'zygote'
<3>init: cannot find '/system/bin/drmserver', disabling 'drm'
<3>init: cannot find '/system/bin/mediaserver', disabling 'media'
<3>init: cannot find '/system/bin/installd', disabling 'installd'
<3>init: cannot find '/system/bin/keystore', disabling 'keystore'
<3>init: cannot find '/system/bin/sh', disabling 'console'

my android_jb.img contains contents of android_out/root/* , android_out/system android_out output of android build
(android_out = out/platform/target/project/armboard_v7a)

if using -initrd, loads ramdisk contains few binaries. system , other partition mounted in init.rc, , seems mount not happened in logs.