QEMU: How to transfer files from Host to Guest

In virtual box there is a way to transfer files from host to guest and vice versa using the guest additions. In qemu there is a way to transfer files. First install
libguestfs-tools.

apt-get install libguestfs-tools

The libguestfs-tools package contains two important programs guestmount and guestunmount. To mount a image say with qcow2 format run

guestmount -a hd.qcow2 -m /dev/sda  /mnt/dir 

-a hd.qcow2: this option must be followed by a image file.
-m /dev/sda: the disk layout  your image file has. If you don't know just type random disk no and it will give you a layout of the image file.
 /mnt/dir: the mount point of your image.

No you can transfer your file. To unmount run

guestunmount  /mnt/dir

IMPORTANT: Never mount an image when qemu is running. It will corrupt the image.

Reference:

 http://ask.xmodulo.com/mount-qcow2-disk-image-linux.html