Disable writing when not mounted

copied from http://wiki.openwrt.org/doc/howto/usb.storage

You may create an empty file to indicate that the disk is not plugged in so that you don't put files directly onto NAND by doing

touch /mnt/usbstorage/USB_DISK_NOT_PRESENT
chmod 444 /mnt/usbstorage -R

gentoo guest using virtio

kernel config


CONFIG_NET_9P_VIRTIO=m
CONFIG_VIRTIO_BLK=m
CONFIG_VIRTIO_NET=m
CONFIG_VIRTIO_CONSOLE=y
CONFIG_HW_RANDOM_VIRTIO=m
CONFIG_VIRTIO=y
CONFIG_VIRTIO_RING=y
CONFIG_VIRTIO_PCI=y
CONFIG_VIRTIO_BALLOON=m

Virtualization ---> 

  Host kernel accelerator for virtio net (EXPERIMENTAL)

<*>   PCI driver for virtio devices (EXPERIMENTAL)

  Virtio balloon driver (EXPERIMENTAL)

Networking Support --->   Plan 9 Resource Sharing Support (9P2000)  ---> 

  9P Virtio Transport

Device Drivers  --->  [*] Block devices  ---> 

  Virtio block driver (EXPERIMENTAL)

Device Drivers  --->  [*] Network device support  --->

  Virtio network driver (EXPERIMENTAL)

Device Drivers  --->  Character devices  --->

<*> Virtio console

  VirtIO Random Number Generator support

Fedora 16 Virtualizaton setup

yum -y install qemu-kvm libvirt python-virtinst bridge-utils
cat /etc/sysconfig/network-scripts/ifcfg-br0

DEVICE=br0
ONBOOT=yes
TYPE=Bridge
BOOTPROTO=dhcp
STP=on
DELAY=0
NM_CONTROLLED=no


cat /etc/sysconfig/network-scripts/ifcfg-em1
DEVICE=em1
HWADDR=XX:XX:XX:XX:XX:XX
ONBOOT=yes
BRIDGE=br0
TYPE=Ethernet
NM_CONTROLLED=no

systemctl stop NetworkManager.service
systemctl disable NetworkManager.service

chkconfig network on
service network start

reboot