How to build a JuNest image using QEMU

First steps

This tutorial show how to create a JuNest image for x86 inside QEMU. Of course, for images of different architecture (i.e. x86_64, arm, etc) the procedure would be the same.

You first need to create an empty image:

qemu-img create archlinux-i686.img 8G

Install ArchLinux

• You need first to download the ArchLinux image.
• Run QEMU for i386 architecture:

qemu-system-i386 -hda archlinux-i686.img -boot d -cdrom ../archlinux-2014
.12.01-dual.iso -m 1024

• Follow the procedure from the ArchLinux website
  • It is suggested to create just one partition /dev/sda1 on DOS partition table:

cfdisk /dev/sda
mkfs.ext4 /dev/sda1

Install JuNest and needed dependencies for the building

• Configure the ArchLinux in order to install internet with netctl
• JuNest image needs some packages to be already available inside ArchLinux:

pacman -S git base-devel arch-install-scripts 

• (Optional) Install haveged in order to generate entropy. This is useful when you need to create the keyring for pacman:

pacman -Syu haveged
systemctl start haveged
systemctl enable haveged

• Install package-query from AUR

#as user
mkdir package-query && cd package-query
wget https://aur.archlinux.org/packages/pa/package-query/PKGBUILD
makepkg -fsc
#as root
pacman -U package-query.*.xz

• Install JuNest

Build JuNest image

Before building the image it is better to update the OS first:

pacman -Syu

Use JuNest_TEMPDIR if you want to place the building directory on a partition with more space (default is /tmp)

JuNest_TEMPDIR=/tmp/ JuNest -b

Retrieve the JuNest image

• fdisk gives the start and end offsets in 512-byte sectors, so multiply by 512 to get the correct offset to pass to mount:

fdisk -l archlinux-i686.img

• Mount the QEMU image to extract the JuNest tar.gz file:

mkdir /mnt/archlinux-i686
mount -o loop,offset=OFFSET archlinux-i686.img /mnt/archlinux-i686