Mount qemu harddisk image in host system

Recently I got to copy a lot of files from a qemu guest, and I think using network is too slow, so I googled for solutions to mount qemu image in host system (when guest is shutdown). And it turns out that only raw images are supported, therefore the first step is to convert the image format:

qemu-img convert –f qcow2 origin.qcow –O raw temp.raw

Then I fount in archlinux wiki that I should mount with –loop,offset=32256 option, but I fail to figure out where 32256 comes. Luckily I remenbered how I delt with dd images. Just get the offset with fdisk:

fdisk –u –l temp.raw

Then I have the sector size (512 in my case) and the offset (2048, start sector of my partation), so the offset should be 512*2048=1048576. (btw, you can calculate with bc: echo ‘512*2048’ | bc)

mount –t ext4 –o loop,offset=1048576 temp.raw /mnt/some-path

That’s it :)

QEMU "host only network"

Abstract: Setup an LAN network of only the host and guest.

Recently I'm trying something on qemu and want to access the guest from the host more freely than user mod port redirect, but I do not want to expose my guest to the host network. All I did is to wrap everything into a script:

#!/bin/sh

HOSTIP="192.168.1.250"
GUESTIP="192.168.2.10"
NETMASK="255.255.255.0"
USERID=`whoami`
IFNAME=`sudo tunctl -b -u $USERID`

sudo ifconfig $IFNAME $HOSTIP netmask $NETMASK up

echo ":: Host IP is $HOSTIP"
echo ":: Run the follwing command in guest to set IP and gateway:"
echo " # ifconfig eth0 $GUESTIP"
echo " # route add default gw $HOSTIP"
echo ":: Starting QEMU with TUN/TAP network..."

qemu -hda webdev.qcow \
     -boot c -m 256 \
     -k en-us -localtime\
     -net nic,vlan=0,model=rtl8139 \
     -net tap,vlan=0,ifname=$IFNAME,script=no,downscript=no

sudo tunctl -d $IFNAME
HOSTIP="19

Btw, I find sticky note gadget on iGoogle a great tool to share a couple of lines between machines - I'm writing on my Windows laptop and the script is in my Linix desktop, just a few paste and copy brings the script here :)