How to do it...

Follow these steps outlined to install a new Debian Linux distribution on the raw image:

1.  Mount the root partition from the Network Block Device (NBD) device and ensure that it was mounted successfully:  

root@kvm:~# mount /dev/nbd0p2 /mnt/    
root@kvm:~# mount | grep mnt    
/dev/nbd0p2 on /mnt type ext4 (rw) 
root@kvm:~#

1.  Install the latest stable Debian distribution on the root partition mounted on /mnt from the specified public repository:

root@kvm:~# debootstrap --arch=amd64 --include="openssh-server vim" stable /mnt/ http://httpredir.debian.org/debian/    
...    
I: Base system installed successfully.    
root@kvm:~#

1.  Ensure the root filesystem was created, by listing all the files at the mounted location: 

root@kvm:~# ls -lah /mnt/    
total 100K    drwxr-xr-x 22 root root 4.0K Feb 10 17:19 .    
drwxr-xr-x 23 root root 4.0K Feb 10 15:29 ..    
drwxr-xr-x 2 root root 4.0K Feb 10 17:19 bin    
drwxr-xr-x 2 root root 4.0K Dec 28 17:42 boot    
drwxr-xr-x 4 root root 4.0K Feb 10 17:18 dev    
drwxr-xr-x 55 root root 4.0K Feb 10 17:19 etc    
drwxr-xr-x 2 root root 4.0K Dec 28 17:42 home    
drwxr-xr-x 12 root root 4.0K Feb 10 17:19 lib    
drwxr-xr-x 2 root root 4.0K Feb 10 17:18 lib64    
drwx------ 2 root root 16K Feb 10 17:06 lost+found    
drwxr-xr-x 2 root root 4.0K Feb 10 17:18 media    
drwxr-xr-x 2 root root 4.0K Feb 10 17:18 mnt    
drwxr-xr-x 2 root root 4.0K Feb 10 17:18 opt    
drwxr-xr-x 2 root root 4.0K Dec 28 17:42 proc    
drwx------ 2 root root 4.0K Feb 10 17:18 root    
drwxr-xr-x 4 root root 4.0K Feb 10 17:19 run    
drwxr-xr-x 2 root root 4.0K Feb 10 17:19 sbin    
drwxr-xr-x 2 root root 4.0K Feb 10 17:18 srv    
drwxr-xr-x 2 root root 4.0K Apr 6 2015 sys    
drwxrwxrwt 2 root root 4.0K Feb 10 17:18 tmp    
drwxr-xr-x 10 root root 4.0K Feb 10 17:18 usr    
drwxr-xr-x 11 root root 4.0K Feb 10 17:18 var    
root@kvm:~#

1. Bind and mount the devices directory from the host to the image filesystem:   

root@kvm:~# mount --bind /dev/ /mnt/dev    
root@kvm:~#

1. Ensure that the nbd devices are now present inside the mount location:

root@kvm:~# ls -la /mnt/dev/ | grep nbd0    
brw-rw---- 1 root disk 43, 0 Feb 10 18:24 nbd0    
brw-rw---- 1 root disk 43, 1 Feb 10 18:26 nbd0p1    
brw-rw---- 1 root disk 43, 2 Feb 10 18:26 nbd0p2    
root@kvm:~#

1.  Change the directory namespace to be the root filesystem of the image and ensure the operation succeeded:  

root@kvm:~# chroot /mnt/    
root@kvm:/# pwd
/    
root@kvm:/#

1.  Check the distribution version inside the chroot environment:

root@kvm:/# cat /etc/debian_version
8.7    
root@kvm:/#

1. Mount the proc and sysfs virtual filesystems inside the chrooted environment:

root@kvm:/# mount -t proc none /proc    
root@kvm:/# mount -t sysfs none /sys    
root@kvm:/#

1. While still inside the chrooted location, install the Debian kernel metapackage and the grub2 utilities:  

root@kvm:/# apt-get install -y --force-yes linux-image-amd64 grub2

1. Install GRUB on the root device:  

root@kvm:/# grub-install /dev/nbd0 --force   
Installing for i386-pc platform.
grub-install: warning: this msdos-style partition label has no post-MBR gap; embedding won't be possible.
grub-install: warning: Embedding is not possible. GRUB can only be installed in this setup by using blocklists. However, blocklists are UNRELIABLE and their use is discouraged..
Installation finished. No error reported.    
root@kvm:/#

1.  Update the GRUB configs and the initrd image:   

root@kvm:/# update-grub2    
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.16.0-4-amd64
Found initrd image: /boot/initrd.img-3.16.0-4-amd64
done   
root@kvm:/#

1.  Change the root password of the guest: 

root@kvm:/# passwd    
Enter new UNIX password:    
Retype new UNIX password:    
passwd: password updated successfully    
root@kvm:/#

1. Allow access to the pseudo Terminal inside the new guest OS:   

root@kvm:/# echo "pts/0" >> /etc/securetty    
root@kvm:/#

1. Change the systemd run level to the multi-user level:  

root@kvm:/# systemctl set-default multi-user.target    
Created symlink from /etc/systemd/system/default.target to /lib/systemd/system/multi-user.target.    
root@kvm:/#

1. Add the root mountpoint to the fstab file, so it can persist reboots:

root@kvm:/# echo "/dev/sda2 / ext4 defaults,discard 0 0" > /etc/fstab

1. Unmount the following filesystems as we are done using them for now: 

root@kvm:/# umount /proc/ /sys/ /dev/

1. Exit the chrooted environment:   

root@kvm:/# exit    
exit    
root@kvm:~#

1. Install GRUB on the root partition of the block device associated with the raw image:   

root@kvm:~# grub-install /dev/nbd0 --root-directory=/mnt --modules="biosdisk part_msdos" --force 
Installing for i386-pc platform.
grub-install: warning: this msdos-style partition label has no post-MBR gap; embedding won't be possible.
grub-install: warning: Embedding is not possible. GRUB can only be installed in this setup by using blocklists. However, blocklists are UNRELIABLE and their use is discouraged..
Installation finished. No error reported.    
root@kvm:~#

1. Update the GRUB configuration file to reflect the correct block device for the guest image: 

root@kvm:~# sed -i 's/nbd0p2/sda2/g' /mnt/boot/grub/grub.cfg    
root@kvm:~#

1.  Unmount the nbd0 device:   

root@kvm:~# umount /mnt    
root@kvm:~#

1. Disassociate the nbd0 device from the raw image:   

root@kvm:~# qemu-nbd --disconnect /dev/nbd0    
/dev/nbd0 disconnected    
root@kvm:~#